by shalini srivastava-modi - university of toronto t-space · v and it is impossible to thank my ma...
TRANSCRIPT
EVALUATING THE ABILITY of eQUEST SOFTWARE TO SIMULATE LOW-
ENERGY BUILDINGS IN A COLD CLIMATIC REGION
by
Shalini Srivastava-Modi
A thesis submitted in conformity with the requirements for Master of Science
Department of Geography and Planning of
University of Toronto
© Copyright by Shalini Srivastava-Modi (2011)
ii
ABSTRACT
Evaluating the Ability of eQUEST Software to Simulate Low-Energy Buildings in a
Cold Climatic Region
in partial fulfillment for the degree of
Master of Science, Department of Geography and Science, University of Toronto, 2011.
Supervisor: Dr. L.D. Danny Harvey
Review Committee members: Dr. Kim Pressnail, Dr. Russell Richman, Dr. Brad Bass
Building Simulation is widely used for understanding how a building consumes energy and for
assessing design strategies aimed at improving building energy efficiency. The present research
study uses eQUEST, a popular simulation software. Various simulations are done here to
analyse and critically comment on the best design strategies to be used in order to vastly
reduce the energy consumption of a recently constructed small (1800 m2 floor area)
commercial building in Brampton, Ontario, which is a heating dominated region. The limitations
faced with eQUEST while simulating the modified design are critiqued.
A complete understanding of the building science and heat flow through the building envelope
has been applied to modify the building in question. After all the changes applied, the overall
heat load of the building was reduced to 15 kWh/m2/yr and the overall energy consumption
reduced by 60 percent.
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DEDICATION
To Ma and Dad
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ACKNOWLEDGEMENT
There are a myriad of people I would like to thank for supporting me on this journey. They are -
Professor Harvey, for believing in me, sponsoring me and having immense patience as my
journey went through numerous ups and downs. He is a dedicated person in the field of
energy efficiency and I have learnt a lot from him. Our discussions were always very
informative and showed me a very clear picture of the subject matter. It has been a privilege
to be his student.
Prof. Kim Pressnail, Prof. Russell Richman and Dr. Brad Bass for being in my Review
Committee and providing critical remarks.
Prof. Ted Kesik, Prof. Jyotirmay Mathur, Mr. Brian Fountain, Mr. Antoni Paleshi, Mr. Kamel
Haddad and Mr. Shivraj Dhaka for technical support with eQUEST.
Mr. Gahir for providing with the drawings of the building, which has been the one in
question in this research work and Mr. Iqbal for answering various design questions related
to the building.
My mentor Mr. Rishi Kumar and friends Abhishek Bathula, Shailza Singh and Rujul Pathak for
sparing their time and discussing my work with me as well as providing technical support
with the software.
All the wonderful people I met during my visit to India who offered me a helping hand to
progress in my work without expecting anything at all in return.
Bharti Aunty for her indispensable contribution and support by taking care of my boys and
home in general.
My little boys Aarav and Anshul sure deserve big thanks for letting their Mamma work as
they waited for her to be with them!
Anuj and Chittal for their unconditional and very valuable support.
Ma and Dad for loving me so much, making me the person I am today, having faith in me and
encouraging me whenever I felt low. My Dad for all the strength and support he provided
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and it is impossible to thank my Ma enough for what she has done for me, for being around
for months together during my thesis period, and for all her support and prayers.
Lastly, Hemen, for letting me pursue my dream, taking pride in me and my work, and
supporting me as much as he could. I could never have accomplished this work without his
love, support, encouragement, and faith in me.
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TABLE OF CONTENTS
ABSTRACT...................................................................................................................................ii
DEDICATION...............................................................................................................................iii
ACKNOWLEDGEMENT................................................................................................................iv
TABLE OF CONTENTS..................................................................................................................vi
ACCRONYMS..............................................................................................................................ix
DEFINITIONS...............................................................................................................................x
LIST OF FIGURES.........................................................................................................................xi
LIST OF TABLES..........................................................................................................................xiii
1. INTRODUCTION...............................................................................................................1
1.1 Background...............................................................................................................1
1.2 Commercial Buildings in Canada..............................................................................3
1.3 Research Approach...................................................................................................4
2. BUILDING SIMULATION...................................................................................................7
2.1 Energy Simulation.....................................................................................................7
2.2 Simulation tools and comparison.............................................................................9
2.3 eQUEST as a simulation tool....................................................................................11
2.3.1 Engine in eQUEST.........................................................................................12
2.3.2 Building Blocks of Simulation.......................................................................12
2.3.3 Types of Heat Transfer Surfaces in DOE-2...................................................15
2.3.4 Observed and noted limitations of eQUEST................................................15
3. ENERGY EFFICIENCY MEAURES (EEMs)..........................................................................18
3.1 Building shape, form and orientation......................................................................18
3.2 Thermal mass..........................................................................................................19
3.3 Glazing fraction.......................................................................................................20
3.4 Window properties.................................................................................................23
3.5 Opaque envelope components................................................................................24
3.6 Air tightness.............................................................................................................25
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3.7 Shading....................................................................................................................26
3.8 HVAC........................................................................................................................27
3.8.1 All air system................................................................................................28
3.8.2 Hydronic system...........................................................................................28
3.8.3 Ventilation....................................................................................................29
3.8.4 Production of Heat/coldness........................................................................33
3.8.5 Distribution of Heat/coldness.......................................................................36
3.8.6 Heat recovery...............................................................................................37
3.9 Domestic hot water.................................................................................................37
3.10 Lighting...............................................................................................................38
3.11 Energy use savings in various buildings across the globe...................................40
4. THE CASE STUDY.............................................................................................................41
4.1 The Building.............................................................................................................41
4.2 Climate of Southern Ontario....................................................................................43
4.3 As-is case design parameters...................................................................................43
4.3.1 Envelope.......................................................................................................43
4.3.1.1 External Wall Construction.....................................................................44
4.3.1.2 Roof Construction...................................................................................45
4.3.1.3 Floor Construction (Slab on grade).........................................................46
4.3.1.4 Fenestration............................................................................................47
4.3.1.5 Thermal resistance of Envelope..............................................................47
4.3.2 Occupancy, Lighting and Equipment............................................................49
4.3.3 Infiltration.....................................................................................................50
4.3.4 HVAC system.................................................................................................50
4.3.5 Schedules......................................................................................................50
4.4 As-is Case Results.....................................................................................................51
4.5 Analysis of As-is Case Results...................................................................................54
4.6 Rough manual calculations to check the heat load for the As-is case.....................54
5. MODIFICATIONS, RESULTS AND ANALYSIS.....................................................................58
5.1 Orientation (OT).......................................................................................................61
5.2 Modified glazing fraction (WF).................................................................................63
5.3 Added shading on windows (WS).............................................................................64
5.4 Window improvement (WI).....................................................................................64
5.5 Envelope improvements (ENV)................................................................................65
5.6 Infiltration (INF)........................................................................................................68
5.7 Lighting (LGT)............................................................................................................69
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5.8 Heat Recovery (HR)...................................................................................................70
5.9 Mechanical systems (HVAC).....................................................................................72
5.10 Primary Energy use...........................................................................................74
5.11 Financial Analysis..............................................................................................76
5.11.1 Energy Cost ................................................................................................76
5.11.2 Net Present Value (NPV).............................................................................77
6. CONCLUSIONS.......................................................................................... ....................80
6.1 Challenges of eQUEST............................................................................................80
6.2 Conclusions made on the analysis of all simulations done in this research work...81
6.3 Suggestions for future research based on this study.............................................82
REFERENCES..............................................................................................................................84
APPENDIX..................................................................................................................................86
ix
ACCRONYMS
ACH50 Air Change per Hour at 50 Pascal Pressure difference
ASHRAE American Society of Heating and Air‐conditioning Engineers
CFD Computational Fluid Dynamics
DOE Department of Energy, USA
DSF Double Skin Façade
IAQ Indoor Air Quality
LEED Leadership in Energy and Environmental Design (A rating system/tool for building to measure how sustainable/energy efficient it is)
HDD Heating Degree Days
VIP Vacuum Insulated Panel
VAV Variable Air Volume
MV Mixing Ventilation
DV Displacement Ventilation
DCV Demand Controlled Ventilation
COP Coefficient of Performance
NPV Net Present Value
x
DEFINITIONS
GHG – Green House Gases are gases in the atmosphere that absorb and emit radiation
within the thermal infrared range. This process is the fundamental cause of the
greenhouse effect. The primary greenhouse gases in the earth’s atmosphere are water
vapour, carbon dioxide, methane, nitrous oxide, and ozone.
EUI – Energy Utilization Index is the total energy (electricity and gas) used annually per
unit conditioned space.
HUI – Heating Utilization Index is the total energy used for heating annually per unit
conditioned space.
HDD – Heating Degree Day is a measurement designed to reflect the demand for energy
needed to heat a building. HDDs are defined relative to a base temperature – the
outside temperature above which a building needs no heating, taken to be 18˚C.
Azimuth – is the degree measure from the North.
Window Reveals – A reveal is the visible part of each side of a window or door, which is
not covered by the window frame.
Human Thermal Comfort – It is the condition of mind which expresses satisfaction with
the thermal environment. The environmental factors affecting thermal comfort include
air temperature, radiant temperature, air velocity and humidity. The personal factors
affecting thermal comfort are clothing and individual’s metabolic heat.
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LIST OF FIGURES
Figure 1.1 World marketed energy consumption (EJ), 1990-2035 (Source: EIA 2007)
Figure 1.2 Distribution of energy use in commercial building in Canada (Source: NRTEE
2009)
Figure 1.3 Growth in energy consumption in commercial buildings in Canada (Source:
NRTEE 2009)
Figure 3.1 Sunpath in summer at a northern latitude
Figure 3.2 Sunpath in winter at a northern latitude
Figure 3.3 Bad window frame installation
Figure 3.4 Recommended window frame installation
Figure 3.5 Use of shading to prevent summer heat gain and permit winter heat gain
Figure 3.6 Hybrid ventilation concept graphic
Figure 4.1 Graphical representation of the building
Figure 4.2 Geometrical representation of the building
Figure 4.3 Floor Plan of First Floor (with units as zones)
Figure 4.4 Floor Plan of Second Floor (with units as zones)
Figure 4.5 Section of the external wall of the existing building
Figure 4.6 The overall electric consumption in kWh/m2/yr
Figure 4.7 The overall gas consumption in kWh/m2/yr
Figure 4.8 Percentage breakdown of electricity use in the building
Figure 4.9 Percentage breakdown of natural gas use in the building
Figure 4.10 Cumulative energy use in kWh/m2/yr throughout the year by various factors
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Figure 5.1 Variation in the total energy demand (kWh/m2/yr)
Figure 5.2 Variation in heating energy demand (kWh/m2/yr)
Figure 5.3 Variation in cooling energy demand (kWh/m2/yr)
Figure 5.4 Variation in vent fan energy demand (kWh/m2/yr)
Figure 5.5 Original orientation of the building (snapshot of eQUEST screen)
Figure 5.6 Changed orientation (snapshot of eQUEST screen)
Figure 5.7 Thermal-bridge-free
Figure 5.8 NOT thermal-bridge-free
Figure 5.9 Best practices of envelope construction
Figure 5.10 Schematic diagram of Heat Exchanger
xiii
LIST OF TABLES
Table 2.1 Characteristics of eQUEST (Source: Crawley et al, 2005)
Table 3.1 Illustration of the effect of building shape on the surface area: volume ratio,
average
Table 4.1 Properties of materials consisting of various layers of existing external wall
construction
Table 4.2 Properties of materials consisting of various layers of existing Roof construction
Table 4.3 Properties of materials consisting of various layers of existing Floor construction
Table 4.4 Thermal Resistance of various elements of the existing envelope
Table 4.5 Area, occupancy, lighting and equipment power densities of all the zones
Table 4.6 Rough manual calculation for total heat loss for the As-is-case
Table 4.7 Manual heat requirement and heat load calculations for all (relevant) cases
Table 5.1 Nomenclature used to represent various cases
Table 5.2 Details of the windows chosen for modified building
Table 5.3 The total energy costs for the original and final cases per square meter of the
building area
Table 5.4 The Net Present Value of the annual savings per square meter of the floor area
for various rates of inflation
1
CHAPTER 1
INTRODUCTION
1.1 Background
Fossil Fuels are the biggest source of primary energy. Unfortunately, combustion of fossil fuels
emits carbon dioxide (CO2) and other greenhouse gases, as well as, pollutants, which contribute
to global warming, air and water pollution, and other damage to the earth’s ecosystem.
Additionally, the world’s energy consumption continues to increase, which exacerbates the
problem of environmental detriment. In the IEO 2009 reference case, world energy
consumption is projected to increase from 522 EJ in 2006 to 570 EJ in 2015 and 730 EJ in 2030.
It is forecasted to be about 2 percent lower than projected in the International Energy Outlook
2008 (IEO2008), largely as the result of a slower overall rate of economic growth. From the
retrieved data of US Energy Information Administration, the graph (Figure 1.1) has been drawn
and it clearly says that from the year 2000, the energy usage in this world has and will increase
tremendously.
Figure 1.1 World marketed energy consumption (EJ), 1990-2035 (Source: EIA 2007)
375 395 427
522 570
622 670
728 760
0
100
200
300
400
500
600
700
800
1990 1995 2000 2007 2015 2020 2035 2030 2035
History
Projections
2
Energy use in buildings accounted for 2.12 Gt Carbon emissions in 2002 globally, which is 33%
of total energy-related emission in the world. The Special Report on Emissions Scenarios (SRES)
projects these emissions to grow to 3 Gt (B2 scenario) and 4.25 Gt Carbon by 2030. Thus,
energy use in buildings is a strong contributor to global warming. At the same time, there lies a
huge potential of emission mitigation in the building sector. It is, therefore, of extreme
importance and urgency that building engineers and architects get intensely involved in
reducing energy use in buildings – both in new buildings, as well as, through renovation of
existing buildings.
It has been demonstrated that there lies a possibility of achieving up to 80% of saving in energy
usage in new residential and commercial buildings (Harvey, 2006, section 14.2.2). However,
there lies a huge stock of inefficient existing buildings. The extent to which energy use in the
existing buildings can be reduced will determine our long term ability to reduce energy use in
the building sector. Various retrofit techniques and measures may be implemented in order to
improve the energy efficiency of existing buildings. At the same time, various kinds of
modifications can also be done in the design of new buildings in order to minimize their energy
use. Electricity instead of fossil fuels can be used to meet these vastly reduced energy loads and
electricity produced using solar, wind or other renewable resources can eventually be used
instead of electricity produced from coal fired power plants. This can be a huge step towards
reducing carbon emissions by the building sector.
In order to bring down the energy demand of a building, it is important to understand how
energy is distributed throughout the building and how each design parameter contributes to
the energy consumption of the building. Figure 1.3 shows the average distribution of energy in
commercial buildings of Canada. Building simulation can be an effective tool, both for
understanding how a building consumes energy and for assessing building design strategies
aimed at improving building energy efficiency.
3
Figure 1.2 Distribution of energy use in commercial building in Canada (Source: NRTEE 2009)
The present research study uses eQUEST, a popular DOE-2 (defined under Definitions) program
used by the simulation community. Various simulations are done here to analyse and critically
comment on the best design strategies to be used in order to vastly reduce the energy
consumption of a recently constructed small (1800 m2 floor area) commercial building in
Brampton, Ontario. The building in this study has an area of 1800 m2; it has two floors with
retail stores on the first floor and offices on the second floor. The following subsection
describes the profile of commercial buildings in Canada briefly.
1.2 Commercial buildings in Canada
There are more than 440,000 commercial buildings in Canada, taking up approximately 672
million square metres of floor space. They account for 14% of end-use energy consumption and
13% of the country’s carbon emissions. Space and water heating account for 65% of energy
used in commercial buildings in Canada. Natural gas accounts for 52% of the energy used by the
sector and electricity accounts for 36%.
51%
7%
7%
8%
9%
5%
14% SPACE HEATING
OTHER NON-SUBSTITUTABLES
AIR CONDITIONING
LIGHTING
REFRIGERATION
OTHER SUBSTITUTABLES
WATER HEATING
4
Between 1990 and 2005, energy consumption by Canada’s commercial buildings increased by
25% and carbon emissions increased by 27% (NRTEE, 2009). Between 1990 and 2003, energy
intensity increased from 1.69 GJ/m2/yr to 1.84 GJ/m2/yr, but by 2005 it decreased to 1.62
GJ/m2/yr, indicating improvement in recent years. Figure 1.3 shows the growth in energy
consumption in commercial buildings in Canada.
Figure 1.3 Growth in energy consumption in commercial buildings in Canada (Source: NRTEE,
2009)
1.3 Research approach
Objectives and questions -
For the last few decades, varieties of building energy simulation programs have been developed
and are in use throughout the building simulation community. These building energy simulation
programs have different features and various capabilities. eQUEST is one of the most popular
and widely used building energy simulation programs. The reason for its popularity is the fact
that it combines simplified input wizards with detailed simulation tools and has the potential of
meeting various needs, both of architects and engineers, such as integrating graphical results
5
with context-sensitive guidance. It is a tool that can be used in the conceptual design stage,
when little is known about the building, as well as in the final design stages when most project
details have been finalized.
eQUEST has been chosen for this study to explore the practical limitations of such a popular
program in simulating extremely low energy buildings. A cold climatic region, Greater Toronto
Area, has been chosen, which is heating dominated. The concept used is to reduce the building
energy loads as much as possible and then meet them using the most efficient ways and
systems. An effort has been made to understand the challenges that eQUEST possesses in
designing the most energy efficient systems to provide the reduced energy (mostly heating)
loads. If these challenges are eliminated from this program, this can be truly a very useful tool
in the industry, given all its advantages that include ease in using, graphical results and more.
In this research work, simulations for various modifications are carried out. While applying the
upgrades, the major challenges faced by eQUEST are observed and documented. At the same
time, the behaviour of variation of various energy loads when applying the upgrades is
observed and analysed.
The objectives of this study are as follows:
1. To understand eQUEST software and its potential
2. To model the building in question in eQUEST
3. To apply various upgrades in order to achieve large energy use reduction and meet
them by most efficient ways.
4. To identify challenges faced by the software
5. To critically analyze the energy use pattern by changing various design parameters
6. To make substantial recommendations regarding designing of new commercial buildings
in a cold climatic region
This study specifically answers the following questions –
1. What is the extent of energy load reduction that can be achieved according to the
eQUEST software?
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2. How does building energy load behave when different upgrades are applied?
3. What are the parameters of commercial building design that affect the energy use the
most and should be considered critically while designing new buildings?
4. How much energy use reduction has been observed in practice in some existing
buildings around the world by applying similar upgrades?
Methodology –
The research approach used in this study has the following steps -
Collect data regarding the commercial plaza to be modeled
Prepare schedules for occupancy, lighting and equipments using actual data
Develop a detailed building energy simulation model of the building in question in
eQUEST
Apply various upgrades in the existing building design, which include orienting the
building so maximum windows face south, maximizing window fraction on south facade,
introducing daylight sensors, improving windows, infiltration, envelope, lighting, and
HVAC system
Document the challenges faced with eQUEST while applying these upgrades
Critically analyze the energy use pattern with each upgrade and suggest the most
efficient parameters for building design for new commercial buildings.
Scope -
The study of the software as well as the critical analysis of the building energy use is
presented only for the upgrades chosen.
Cost implications for these upgrades are also out of scope of this research work. The
suggestions made do not consider the cost implications or payback period but are
purely on the basis of the energy load reduction achieved by the upgrades.
7
CHAPTER 2
BUILDING SIMULATION
2.1 Energy Simulation
The energy used to heat or cool a building depends on the distribution of temperature within
the building, as well as, on the properties of the thermal envelope and the rate of air exchange
between inside and outside of the building. The temperature distribution plays an important
role, because the rate of heat flow across a window or wall depends on the difference in
temperature between the window or wall surface and the air temperature adjacent to the
surface. It also depends on the heat transfer coefficient between the inner envelope surface
and interior air, which in turn depends on the rate of air movement and degree of turbulence.
The detailed pattern of air movement depends on the mechanical ventilation system, as well
as, on the temperature distribution. In turn, the temperature distribution depends on the air
movement and of the temperatures on all the room surfaces. This creates a feedback loop – the
temperature distribution and boundary conditions depend, in part, on the air movement, which
depends (in part) on the temperature distribution and the boundary conditions. Computing this
interaction for an entire building requires solving the equations of fluid dynamics and
temperature on a fine grid that corresponds to the geometry of the building in question. This
approach is referred to as Computational Fluid Dynamics (CFD) and requires substantial
computing power and memory (Harvey, 2006, Appendix D). CFD calculates the thermal comfort
of a building accurately, but due to extremely complicated nature of the calculations involved,
it is not used extensively. Instead, a much simpler approach has been in use. This treats
different rooms in a building as a series of boxes. The temperature inside each of these boxes is
assumed to be uniform. The heat flow across each surface bounding each box is computed
using the following equation:
q = temperature difference / thermal resistance = ∆T / R
q (heat flow) has units of watts per square metre (W/m2).
8
Various sources of heat, such as lighting, fans, equipment, people, etc. can be included while
evaluating net heating or cooling requirements. The temperature change over a given period of
time depends on the net of all fluxes into or out of the box during that time interval. This
approach is called the Energy Simulation (ES) approach and is always used when computer
simulation models are used as a part of the design process. The down side of the Energy
Simulation programs is that they cannot accurately predict the energy use for systems that
produce non-uniform temperatures within the building, such as displacement ventilation. Also
they cannot provide information on airflow entering a building through natural ventilation,
whereas such airflow is important for predicting the interior air temperatures and the heating
and cooling loads in naturally ventilated buildings.
Technological advancements in computer software have provided tools that are very effective
at predicting energy performance once the building is operational. An energy simulation tool
models the thermal, visual, ventilation and other energy consuming processes taking place
within a building to predict its energy and environmental performance. During the calculation
process, these tools take into account the external climatic factors, internal heat sources,
building materials and systems to accurately model the building. Building energy simulation is a
powerful method for studying energy performance of buildings and for evaluating architectural
design decisions, as well as, choices for construction materials and methods. Complicated
design issues can be examined and their performance can be quantified and evaluated.
Simulation and energy analysis are essential to designers in developing effective forms and
components for their buildings. Building energy simulation is a process that can be used for
analysing the energy performance of a building. Such tools support the integrated use of
multiple investigation and visualization during the design evolution process—from the
conceptual and schematic phases to the detailed specifications of building components and
systems.
There is a wide range of simulation tools available today, which help predict various aspects of
building behaviour, such as, energy performance, acoustical performance, fire movement, anti–
9
seismic performance, lifecycle assessment simulators, etc. Energy performance simulation tools
allow designers to:
• Predict thermal behaviour of buildings in relation to their outdoor environment.
• Envisage the impact of daylight and artificial light inside buildings.
• Model the impact of wind pattern and ventilation on energy use.
• Estimate the size/capacity of equipment required for thermal and visual comfort.
• Calculate the effect of various building components on each other and predict resulting conditions.
• Check for compliance with building codes.
• Consider the building as a single integrated system.
Building energy simulation has been playing an increasingly significant role not only in building
design, but also in operation, diagnostics, commissioning and evaluation of buildings. It can
help designers compare various design options and arrive at the most energy efficient design in
view of cost-effectiveness. Building energy simulation can also help facility managers and
engineers identify energy saving potentials and evaluate the energy performance and cost
effectiveness of energy saving measures to be implemented. There are many building energy
simulation software available now. Some are simplified energy analysis tools that only provide a
quick analysis of annual energy use of buildings, but some use more detailed models and run on
hourly basis that provide detailed hour-by-hour energy use of buildings. No matter which
software is used, calibration of simulation models is necessary and crucial for the accuracy and
usability of energy simulation results. The calibration process compares the results of the
simulation with measured data and tunes the simulation until its results closely match the
measured data. Whole building simulation tools are widely used and are applied to the entire
building as an integrated system; these take into account all parameters and components
together.
10
2.2 Simulation tools and comparison
A large number of simulation tools have been developed over the last few decades. The
building energy simulation software tool web page, run by the US Department of Energy lists
over 240 tools, ranging from research grade software to commercial products. Some important
studies and comparisons have already been done on some of these tools that are discussed
below. This subsection has been largely drawn from Rallapalli, Hema (2010).
Crawley et al, (2008) describe testing and validation of the building simulation program
EnergyPlus. The results to date show good agreement with well established simulation tools,
such as, DOE-2.1E, BLAST, and ESP. Several testing utilities have been developed to help
automate the task of assuring that each new version of the software is still performing properly.
Selected test results are presented along with lessons learned.
Zhou, (2008) evaluated the energy performance of the VAV (Variable Air Volume) air-
conditioning system and a new simulation module was developed and validated experimentally
in this study, on the basis of EnergyPlus. The differences between average monitored and
predicted data for the total cooling energy and peak cooling power are proved to be within 25%
and 28%.
Crawley, (2005) provides an overview with an up-to-date comparison of the features and
capabilities of twenty major building energy simulation programs. The comparison is based on
information provided by the program developers in the following categories: general modeling
features, zone loads, building envelope, daylighting, infiltration, ventilation, multizone airflow,
renewable energy systems, electrical systems and equipment, HVAC systems, HVAC equipment,
environmental emissions, economic evaluation, climate data availability, results reporting,
validation, user interface, links to other programs, and availability.
Henninger, (2004) reports on testing the EnergyPlus using IEA HVAC BESTEST E100–E200 series
of tests. HVAC BESTEST is a series of steady-state tests for a single-zone DX cooling system.
Cases range from dry to wet coil, low to high part load, and low to high temperatures. This
11
published test includes three sets of analytical solutions and results from several other
simulation programs for comparison.
Pasqualetto, (1997) presented a case study of a multiple-step validation undertaken to test the
MICRO-DOE2.1E program, which includes the following: (i) response of the model to a given
perturbation in the outdoor environment, (ii) comparison with another modeling tool, (iii)
sensitivity analysis, and (iv) empirical validation using information from a large existing office
building.
Comprehensive testing of building energy analysis software is a difficult task given the large
number of inputs that may be entered and the difficulties in establishing truth standards for all
but the simplest cases. Testing has been guided by a comprehensive test plan which includes
the following types of tests:
• Analytical tests which compare against mathematical solutions,
• Comparative tests which compare results of a given model against other software,
• Sensitivity tests which compare small input changes versus a baseline run,
• Range tests which exercise the program over wide ranges of input values,
• Empirical tests which compare model results against experimental data.
2.3 eQUEST as a simulation tool
Software tools that integrate graphical results with context-sensitive guidance are likely to have
the most appeal for architects. On the contrary, engineers need software tools that can be used
in both the conceptual design stage, when little is known about the building; as well as in the
final design stages, when most project details have been finalized. The eQUEST program
combines simplified input wizards with detailed simulation tools and thus, has potential to
meet these different needs at various stages of the design process.
eQUEST is an easy to use building energy analysis tool combining a building creation wizard, an
energy efficiency measure wizard and a graphical results display module with an enhanced
DOE-2 derived building energy simulation program.
12
The building creation wizard takes a user through the process of creating a building model.
Within eQUEST, DOE-2 performs an hourly simulation of the building based on walls, windows,
glass, people, plug loads, and ventilation. DOE-2 also simulates the performance of fans,
pumps, chillers, boilers, and other energy-consuming devices. eQUEST allows users to create
multiple simulations and view the alternative results in side-by side graphics. It offers energy
cost estimation, daylighting and lighting system control, and automatic implementation of
energy efficiency measures (eQUEST, 2008).
2.3.1 Engine in eQUEST
The simulation "engine" within eQUEST is derived from the latest official version of DOE-2;
however, eQUEST's engine extends and expands DOE-2's capabilities in several important ways,
including interactive operation, dynamic/intelligent defaults, and improvements to numerous
long-standing shortcomings in DOE-2 that have limited its use by mainstream designers.
2.3.2 Building Blocks of Simulation
Building simulation requires that a model of the proposed building be created that is capable of
simulating the important heat flow in the proposed building. Toward this end, the following list
summarizes essential components, steps, or building blocks, in a `how-to` description of the
process of simulation modeling. Before "building" anything, including a simulation model, one
needs to first consider and collect the following:
Analysis Objectives – The simulation model should be approached with a clear understanding of
the design questions to be answered. One has to focus on the important issues and at the same
time, limit the questions. Experience teaches how best to strike this important balance for each
new project.
Building Site Information and Weather Data - Important building site characteristics include
latitude, longitude and elevation, which help the simulation tool to choose the appropriate
weather site for the location. Other site characteristics required includes information about
13
adjacent structures or landscape capable of casting significant shadows on proposed (or
existing) building.
Building Shell, Structure, Materials, and Shades - eQUEST needs information about the walls,
roof, and floor of proposed building only in so far as they transfer or store heat. Geometry
(dimensions) and construction materials of each of the heat transfer surfaces of proposed
building. This will include glass properties of windows and the dimensions of any window
shades (e.g., overhangs and fins). eQUEST itself provides users with simple, user-friendly,
choices for each of these.
Building Operations and Scheduling - This includes information about when building occupancy
begins and ends (times, days of the week, and seasonal variations such as for schools), occupied
indoor thermostat set points, and HVAC and internal equipment operation schedules. eQUEST
has default operations schedules based on building type.
Internal Loads - Heat gain from internal loads (e.g., people, lights, and equipment) can
constitute a significant portion of the energy requirements in large buildings, both from their
direct power requirements and the indirect effect they have on cooling and heating
requirements. In fact, internal loads can frequently make large buildings relatively insensitive to
weather. More importantly, the performance of almost all energy-efficient design alternatives
will be impacted either directly or indirectly by the amount of internal load within a building.
HVAC Equipment and Performance - Good information regarding HVAC equipment efficiency
will be important to the accuracy of any energy use simulation. eQUEST assumes default HVAC
equipment efficiencies according to California's energy standard. Where possible, equipment
efficiencies specific to each analysis should be obtained, e.g., from the building design
engineers or directly from equipment manufactures. Most HVAC equipment manufactures now
publish equipment performance data on their web sites.
Utility Rates - A great strength of detailed energy use simulation using eQUEST is the ability to
predict hourly electrical demand profiles that can then be coupled with full details of the
applicable utility rates (tariffs).
14
Economic Parameters – This facilitates recommend life-cycle economics above simple payback
methods of economic analysis. Because energy efficiency investments usually return benefit
over the entire life of the building or system, considering their lifecycle impact is most
appropriate.
HVAC Zoning - HVAC zoning recognizes that load profiles seen by different spaces in a building
differ. Identifying areas with similar load profiles and grouping them under the same
thermostat control improves comfort and may reduce energy use. For example, imagine
measuring indoor air temperatures at many locations throughout a building during hours when
the HVAC fans are turned off. Internal gains, solar gains, and envelope gains/losses would cause
the temperatures to vary with time. If, after some number of hours or days, one carefully
examined the temperature history, grouping together those areas that shared similar profiles,
one would have effectively grouped together those areas of the building that share similar load
characteristics. Each such area or "zone" could, therefore, be adequately controlled by a single
thermostat. In other words, HVAC thermal zoning seeks to group together those areas (rooms)
in a building that share similar load and usage characteristics, for purposes of control. Of
course, this imagined procedure is not how HVAC engineers actually zone any building. Rather,
the methods listed below are followed -
• Calculating and setting up magnitude and schedule of internal loads
• Calculating and setting up magnitude and schedule of solar gains
• Creating a schedule of fan system operations
• Calculating outside air requirements
• Finalizing the intended efficiency measures
• Finalizing the location of thermostats called out on the HVAC plans
Currently, eQUEST provides the user with two automatic zoning schemes, one zone per- floor,
and simple core-vs.-perimeter zoning. Based on this user selection, eQUEST would
automatically zone model.
15
2.3.3 Types of Heat Transfer Surfaces in DOE-2
DOE-2 has four types of heat transfer surfaces on its "palette" to model various types of heat
transfer surfaces in a proposed building: (i) Light-transmitting surfaces, e.g., windows, glass
block walls, sliding glass doors, skylights (DOE-2 thinks of all of these as the same type of heat
transfer surface, i.e., a WINDOW). (ii) Exterior surfaces, e.g., opaque exterior surfaces such as
exterior walls, roofs, and floors (DOE-2 thinks of all of these as the same type of heat transfer
surface, i.e., an EXTERIORWALL) (iii) Interior surfaces, e.g., opaque interior surfaces, such as,
interior walls, interior floors, and interior ceilings. (DOE-2 takes of all of these as the same type
of heat transfer surface, i.e., an INTERIOR-WALL) and (iv) Underground surfaces, e.g., basement
floors and walls, and slab-on-grade. (DOE-2 takes of all of these as the same type of heat
transfer surface, i.e., an UNDERGROUND-WALL).
2.3.4 Observed and noted limitations of eQUEST
This subsection outlines the characteristics of eQUEST as well as some of the limitations. Table
2.1 Details out the characteristics of eQUEST as documented by Crawley et at, 2005.
S. No. Modeling features Capabilities / Limitations
1. HVAC Loads Uses the transfer function method with custom weighting factors. This method is an approximation of the heat balance method, is less accurate and more prone to user error through misapplication of weighting factors. Errors are probably the greatest for building envelope components that have thermal mass.
2. Integrated Simulation of Loads and Systems
Building response to thermal loads is calculated independently of system operation. Load calculations assume building temperatures are in control. Limits applicability of simulation to mechanically conditioned spaces. Limited feedback from HVAC system operation affects building loads and zone temperatures. This prevents DOE-2 from accurately simulating systems and heat transfer where zones are under heated or under cooled.
3. Radiant Exchange Models radiant exchange only through combined radiation / convection coefficients applied to each surface. The convection and radiant heat transfer do not vary with surface temperature for opaque surfaces.
4. Thermal Comfort Cannot directly model zone thermal comfort as it cannot
16
develop surface temperatures.
5. HVAC Systems Systems are predesigned types. This has several limitations: 1) You cannot easily model some systems because there is no predesigned model for them; 2) Enhancements to the program (like evaporative cooling) have to be implemented on each of the different system types. 3) Only one system can be assigned to a zone. You cannot model a system with a perimeter fan coil for heating and a cooling only VAV box for cooling.
6. Displacement Ventilation Systems
Assumes all zones are fully mixed (uniform temperature throughout), which is not appropriate for displacement ventilation systems.
7. Under-Floor Air Distribution Systems
Assumes all zones are fully mixed (uniform temperature throughout), which is not appropriate for UFAD systems. Cannot model supply plenums.
8. Radiant Cooling and Heating Systems
No direct models for radiant cooling or heating systems.
9. Natural Ventilation Can model simplified natural ventilation via operable windows in a few single zone system types (RESYS, RESYS2, PSZ, and EVAP-COOL).
10. Hydronic Loops This feature is only available in Equest (DOE 2.2). It is not available in the reference method DOE-2.1E. In 2.2 only limited configurations of constant and variable flow systems are available.
11. Moisture Migration Cannot model moisture migration.
12. Multiple Time Steps Can only calculate loads on an hourly basis. There is also no feedback between loads and systems
13. Air Emission DOE-2 cannot calculate air emissions directly. It has to rely on post-processing.
14. Water Usage DOE-2 does not have this capability.
15. Renewable Energy DOE-2.2 can model PV.
16. Cogeneration DOE-2 cannot model IC engine or fuel cells.
17. Daylighting and Controls DOE-2 tends to overestimate daylighting benefits.
18. Windows and Shading Controls
DOE-2 has limited shading controls.
19. Demand Response Controls DOE-2 has none.
20. Outdoor Lighting and Controls
DOE-2 cannot.
Table 2.1 Characteristics of eQUEST (Source: Crawley et al, 2005)
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Limitations -
1. The computational engine of eQUEST, DOE-2.2, does not support time steps less than 1
hour, which is sometimes needed to properly study the dynamics of HVAC systems. This
is especially true when there is a variable rate structure for electricity and fuel pricing
and for studying advanced control systems.
2. It is not currently possible to simulate solar thermal systems with eQUEST. These types
of systems are very important for high performance buildings.
3. The daylighting analysis in eQUEST is very basic. This is due to the fact that eQUEST does
not use a geometrically true model of the zones. It keeps track of the surfaces, their
areas, and orientations but does not model the full geometry of the building to allow for
accurate predictions of solar radiation penetration and its distribution inside the space.
4. There is no support for CFD (Computational Fluid Dynamics) analysis.
5. eQUEST has a set of pre-packaged models for certain types of HVAC systems, but does
not provide the user with the possibility of specifying his or her own HVAC system type
through component specification and linkage. One can only specify parameters for the
components of the existing HVAC system types.
(Private communication with Kamel Haddad, NRCan)
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CHAPTER 3
Energy Efficiency Measures (EEMs)
This chapter outlines the opportunities for dramatically reducing energy use in new buildings as
compared to the current conventional practices. The main areas of energy usage in buildings
are assessed, some of the conventional ways of design/construction are briefly described and
then the energy efficient alternatives are discussed. The design of new buildings utilizing all of
the alternatives suggested in this chapter can result in buildings using up to 70-80% less energy
as compared with the existing conventionally designed buildings. Most of these opportunities
have been applied (to the extent that this can be done with eQUEST) to the model of the
building in question and the results are analysed and presented in Chapter 5. The discussion
here is based on Harvey (2006), except where indicated otherwise.
3.1 Building shape, form and orientation
Building shape, form and orientation are architectural decisions that have impacts on heating
and cooling loads, daylighting, passive ventilation, solar heating and cooling, and for active solar
energy systems. Building shape refers to the relative length of the overall dimensions (height,
width, depth); building form refers to small-scale variations in the shape of a building; and
building orientation refers to the direction that the longest horizontal dimension faces. The
impact of these factors is, however, small compared to the impact of more insulation, better
windows, a more air-tight envelope and the use of heat exchangers to recover heat from the
exhaust air in the mechanical ventilation system.
It is commonly found that minimizing the surface area to volume ratio of a building decreases
the heating load for a given insulation system. Even if the thermal resistance of each element
(walls, roof, floor and windows) is fixed, a change in shape of the building will inevitably be
accompanied by a change in the relative proportions of the different facade elements and this
can easily outweigh the impact on heat loss due to increase in surface to volume ratio, when
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the building shape is altered while keeping the volume fixed. Adopting a square, rather than
rectangular, floor plan for a fixed volume, reduces the heat loss coefficient by about 4 percent.
An example of such a calculation is shown in Table 3.1 below.
Case Dimension (m) No.
Of
floors
Area Surface : Floor area
ratio
Weighted
U-value
(W/m2K)
Heat Loss
Coefficient
(W/K)
Walls Roofs Actual Rel Actual Rel
1 100 x 100 1 1200 10000 2.24 1.0 0.32 1780 1.0
2 100 x 50 2 900 5000 1.36 .61 0.49 1670 0.94
2 71.71 x 70.71 2 860.52 5000 1.34 .60 0.48 1603 0.90
Table 3.1 Illustration of the effect of building shape on the surface area: volume ratio,
average envelope U-value and Heat loss coefficient (Reference: Harvey, 2006, Table 3.23)
Note: In every case, the building floor area is 10,000 m2, the floor to floor height is 3 m, and the
window, wall, roof and effective ground U-values are 2.5, 0.5, 0.3 and 0.1 W/m2-K respectively,
Rel = Relative to case 1.
Minimizing surface to volume ratio, specially the roof area and the area of west-facing walls,
also minimizes the summer heat gain from outside. Having narrow buildings and the long axis
along the east-west, would maximize glazing opportunities on the south side, thus maximizing
solar heat gain in winters, which can be controlled during summer months by external shading.
More details of significance of appropriate orientation are detailed in the subsection 3.3 on
Glazing Fraction.
3.2 Thermal mass
In order to maximize the utilization of solar heat captured through direct gain, exposed thermal
mass should be available. Solar radiation striking on a floor can be stored and released at night
if the floor has significant thermal mass, thus avoiding overheating during the day and providing
heat at night. In most passive solar buildings, this is achieved either through massive walls or
through concrete floor. In some solar-air-heating systems, Phase Change Materials (PCMs) are
20
widely used to store heat (Khudhair et al, 2004). These materials change their state or phase
from solid to liquid and back.
High thermal mass can lead to increased energy use for heating buildings that are not occupied
at night. This is because the effectiveness of reducing the thermostat setting at night and
allowing the building to cool is reduced, while the building would warm more slowly in
response to solar heating in the morning, possibly necessitating the use of auxiliary heating
system (Sharma et al, 2009). The net effect of varying thermal mass depends on a number of
factors, such as building occupancy pattern, envelope characteristics, and orientation.
3.3 Glazing fraction
The first step towards passive designing for maximized solar heat gain is to know how the sun
moves through the sky and to orient the building and place the windows accordingly.
In the northern hemisphere, 43˚ N (Brampton’s latitude), during summer, the sun rises north of
due east and sets north of due west, climbing high in the sky at solar noon on the summer
solstice (about 21 June). During winter, the sun rises south of due east and sets south of due
west, climbing not very high in the sky at solar noon on the winter solstice (about 21
December). The further north in the northern hemisphere one goes, the lower the midday
winter sun would be.
At other times in the year, the sun paths will be intermediate between these two extremes.
Only on the equinoxes (21 March and 21 September, approximately), will the sun rise due east
and set due west.
Thus, it is easy to protect south-facing windows with a roof overhang for all but the lowest
winter sun. In cold climatic regions, it is desirable to allow some solar radiation into south-
facing windows during winter, so the roof overhang should not be too wide.
North-facing windows hardly need any shading, since the only time the sun impinges on them is
early in the morning or late in the afternoon in summer, and at those times the angle of
21
incidence is so great that much of the radiation is reflected from the glass or blocked by the
walls, especially if the window is recessed somewhat into the wall.
The biggest problems with solar heat gain and the glare for cooling dominated climates which
direct sun entry can produce, are experienced with east- and west-facing windows. In the
middle of the morning and afternoon, the sun can be low enough in the sky that no overhang
can be effective. In such cases, it is best to block the sun outside, before it reaches the glass,
using tress, shutters, or other such shading methods. Another alternative is to reduce the
glazed areas in the building facing the east and west directions and/or to place unoccupied or
non-air conditioned spaces on the east and west sides of the building, in order to serve as
buffering or insulating zones.
During transition seasons, an east-facing window can provide heat gain when it is most needed,
in order to warm up a building after it has cooled during the night. Thus, for cold regions,
glazing fraction can be maximized on east facing walls. However, a moveable shade would be
required to prevent overheating. West facing windows are more likely to cause overheating.
Any heat that is collected on the west facade will be less helpful in commercial buildings, as it
arrives when workers begin to leave, but will be more advantageous in residential buildings.
The minimum useful winter heat gain and maximum summer heat gain through west-facing
windows might imply that the window area on western facades should be kept very small.
However, substantial energy savings are possible through daylighting. The key is to choose
windows that minimize heat loss and unwanted heat gain. More information on windows is
provided in the subsection 3.4 on window properties.
In assessing the optimal window area for solar heat gain, the impact on summer cooling load
should be determined. Increasing the window area would increase the cooling load even if the
window is shaded, although this penalty can be minimized by the use of insulated external
operable shading devices (such as shutters).
Figures 3.2 and 3.3 illustrate the movement of sun in summer and winter respectively.
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Figure 3.2 Sunpath in
winter at a northern
latitude
Figure 3.3 Sunpath in
summer at a northern
latitude
23
3.4 Window properties
The flow of heat through a window depends on transmission (of solar radiation), emission (of
infrared radiation), conduction (of heat through the glass, through the air between the panes
and through the frames and spacers between the panes), convection (between the panes of
glass), air leakage around the window and infiltration (of outside air).
The window properties affecting such heat flow are –
1. U value (W/m2/K) is the thermal conductivity (W/m/K) divided by the thickness of the
material. The U value (lower the better) can be calculated for -
Center of the glass - by adding the resistances of each layer of glass and taking the
reciprocal of the total resistance or
Frame – the U value of the frame depends on the thermal conductivity of the
framing material.
2. Ψ values (W/m/K) characterises the extended thermal bridges, such as those because of
spacer between panes at the edge of the window, and any thermal bridges around the
frame (which depend on how the window is installed).
3. Solar Heat Gain Coefficient (SHGC) is an indication of the transmission of solar energy
through a window. SHGC is the fraction of the solar radiation incident on a window that
passes through the window, taking into account absorption of some solar radiation by
the window and the transfer of some of this absorbed energy to the interior. For cold
climates, windows with larger SHGC contribute greatly to higher solar heat gain, thus
reducing the amount of heat to be added inside the envelope to maintain the indoor
temperature.
4. Thermal bridges – Heat transfer by transmission does not occur only in the regular
building elements like, walls, roof or windows, but also at corners, edges, junctions, etc.
Places where the regular heat flow through a building element is disturbed, especially
where it is higher in regular construction, are called thermal bridges. Thermal bridge
effect in windows can be minimized by installing the unit in the insulating layer, not in
the load bearing wall and by covering part of the window frame with insulation. Figure
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3.4 illustrates a bad installation of window frame and figure 3.5 illustrates the
recommended installation in order to avoid thermal bridges (PHDCTC, 2010).
3.5 Opaque envelope components (wall, ceiling, basement)
The building envelope consists of the external elements of the building through which the
exchange of heat occurs. The opaque elements of the building envelope are the walls,
basement floor and ceiling. Heat (though these surfaces and otherwise) can be transferred by
conduction, convection, exchange of air and exchange of radiation. To minimize the heat
transfer (minimize the U value) through these surfaces, insulation must be placed with
Figure 3.4 Bad window
frame Installation
Figure 3.5 Recommended
window frame Installation
25
structural elements used to construct these components. Adding insulation itself decreases the
U value or increases the thermal resistance, but the placement of insulation also plays a very
important role. The insulation must be properly placed in order to get maximum benefit from
insulation. The best practices for installing insulation are the following -
To install the insulation on the outside of all building envelope components namely roof,
exterior walls and the base of lowest floor
To install the insulation tightly against the wall surface
To completely seal any puncture, wherever there has been one for construction
purposes (in any of the envelope components)
3.6 Air tightness
The uncontrolled air leakage through the envelope is largely caused due to leaks through cracks
in the building envelope. Sloppy workmanship and joints left unsealed are largely responsible
for a leaky building envelope. The heat loss through the envelope due to an exchange of warm
indoor air with cold outside air depends on the mass flow that occurs and the temperature
difference between outdoor and indoor. Mass flow is directly proportional to the pressure
difference between outdoor and indoor and the area of leaks/cracks. The pressure difference
instead depends on the wind speed and temperature difference between outdoor and indoor.
In a nutshell,
Heat Flow Mass Flow . ∆ T
Mass Flow ∆ P . A
∆ P ∆ T
∆ P also depends on wind speed
Thus, the greater the temperature difference and wind speed, the more heat needs to be
added to the incoming outdoor air in order to maintain the same indoor temperature.
Therefore, the heat loss will be maximum during peak winter. Air leakage from the envelope in
26
cold climates, can contribute up to 40 percent or more of the total building heating load during
winter, but will tend to be less important for summer sensible heat loads (Harvey, 2006, Section
3.7.2).
A mechanical supply and exhaust air ventilation system with heat recovery, combined with
excellent air-tightness of the building envelope are pre-requisite for excellent energy
performance in a building (in cold climatic region). It is critical to construct an extremely air
tight envelope, allowing only 0.2 – 0.6 ACH at 50 Pa pressure difference to avoid the heat losses
due to uncontrolled air exchange through leaks and/or cracks (as advised by the Passive House
Standards, Germany).
Good air-tightness is mainly achieved by appropriate design and construction. Therefore, one
single airtight layer should run around the whole building, so all building element junctions
need be planned and constructed with no leakages.
There is very little information available on natural air exchange rates in commercial buildings.
Fennel and Haehnel (2005) indicate the following rages for typical ACH values at 50 Pascal in
commercial buildings, based on documented studies: 1.1 – 1.6 in Canada, 4.9-7.5 in the US and
6.0-9.1 in the UK. These data imply that ACH values of typical practices in some countries are
larger by a factor of 6-8 than that of a modestly good practice.
3.7 Shading
Shading is an important device to restrict the unwanted solar heat gain in summer. Shading
plays a less crucial role in hot and humid climates, as opposed to hot and dry climate, but it can
be helpful in cold climates during the few months when cooling is required.
Shading should ideally be such that it minimizes solar heat gain in summer and maximizes the
same in winter. Shading devices can be of two kinds - adjustable or fixed. It is not possible to
design a fixed shading device with near zero shading in winter and nearly complete shading in
summer on east or west-facing facades; therefore, adjustable shading devices are preferred to
fixed shading devices on these facades. Also, external louvers are more effective than internal
27
louvers, as only 10% of the sunlight absorbed by the louver is transferred to the interior of a
room in the former case, compared to almost 50% in the latter case (Bansal et al, 1994).
Motorized adjustable louvers and Venetian blinds are common in Europe.
A study on effective solar devices was done by NRCC (National Research Council Canada) in
Ontario (cold climatic region) and the results showed that the exterior roll shutters reduced the
heat loss through windows by about 20% during night time, when they covered the house
windows in the winter. These energy savings were proportionate to the ratio of the window
surface areas to the building`s total envelope surface area. For the summer, roll shutters
reduced daily energy use of A/C unit by about 45%. Figure 3.6 illustrates the use of shading to
prevent summer solar heat gain, which does allow heat gain in winter.
3.8 HVAC (Heating, Ventilation and Air Conditioning) systems
This section details the conventional HVAC design and their energy efficient alternatives. The
discussion starts with all air and hydronic systems, followed by ventilation, and heat and cold
production and distribution.
Figure 3.6 Use of shading to
prevent summer heat gain
and permit winter heat gain
28
3.8.1 All air system
An all air system is one in which hot or cold air is circulated through the ventilation system, in
order to heat or cool the building. Thus, air is used for all the three purposes – heating, cooling
and ventilating. This is not a very effective and efficient system, since it takes much less energy
to distribute heat using water as compared to air, and the airflow requirements for heating or
cooling are far in excess of the airflow required for ventilation alone.
An energy efficient alternative is to supply heat using a variable air volume (VAV) system
(instead of the conventional constant air volume system – which is not even considered in this
study), which supplies only as much air as is required to supply the amount of heat needed. The
air that is supplied through the supply ducts may be taken entirely from the outside and
exhausted to the outside by the return ducts, or a portion of the return air may be mixed with
fresh outside air and recirculated through the building. The incoming fresh air needs to be
cooled and dehumidified in summer, or heated and sometimes humidified in winters. In an all-
air cooling system, the amount of air that needs to be circulated in order to achieve adequate
cooling is so large that fresh air requirements are easily met; ventilation in this case is a
byproduct of the air conditioning.
3.8.2 Hydronic system
As an alternative to the all-air system, the ventilation and heating or cooling functions can be
decoupled by circulating only enough air for ventilation requirements, with any additionally
required heating and cooling provided by circulating hot or cold water through coils. Air in each
room is blown past the coil with a fan, producing a fan-coil system. This requires three
distribution systems – one for air (ductwork) and one each for piping hot and cold water. For
the buildings, which have such thermal building envelope and thermal mass so that frequent
switching between heating and cooling is not necessary, one set of pipes can also do. In such a
case, water flow switches between circulating hot or cold water.
29
The rate at which heat is given off (in watts) by an air or water flow, QH, is give by:
QH = ρcp F (Tsupply-Treturn) = ρcp F ∆T
Where ρ is the density of fluid, cp is the specific heat (J/kg/K), F is the volumetric flow rate
(m3/s), and ∆T is the difference between supply and return temperatures. For air, cp = cpa =
1004.5 J/kg/K and ρ = 1.25 kg/m3 at 10˚C and 1 atm, while for water, c = cpw = 4186 L/kg/K and
ρ = 1000 kg/m3 at 4˚C. From this, it can be seen that, for a given volumetric flow rate and
temperature drop, water delivers 3333 times as much heat as air. Also, heat transfer by water
requires about one hundred times less energy, for given temperature difference, than heat
transfer by air (neglecting differences in pump, fan and motor efficiencies) (Harvey, 2006,
Section 7.1.1).
3.8.3 Ventilation
Ventilation refers to the replacement of interior air with fresh outside air. The fan energy used
to circulate air for ventilation is one of the major contributors to the overall energy use by a
building. That is why, it is crucial to design an efficient ventilation system. Various ways of
providing ventilation are described as follows –
1. Passive Ventilation - It refers to natural ventilation, which typically relies on using
convective air flows that result from the tendency of warm air to rise and cool air to sink
and taking advantage of prevailing winds
i. Operable windows – Many passive ventilation systems rely on the building users to
control window and vents as indicated by site conditions and conditions within the
building.
ii. Double Skin Facade – Such a facade has an inner and an outer wall separated by an
air space that is not actively heated or cooled. The outer facade wall consists of a
single or double glazed glass wall with fixed or adjustable openings, and the inner
facade wall may also consist of a single, double or triple glazed glass wall with
operable windows, or may be partially opaque. The different types of double skin
30
facades include box windows, shaft-box facades, corridor facades and multi storey
facades. The primary energy benefit of double skin facades is their ability to reduce
cooling and ventilation energy use through (i) external shading, (ii) the opportunity to
use natural ventilation when outside conditions permit (saving both cooling and
ventilation energy use); and (iii) the opportunity to use night ventilation by
addressing security concerns and preventing the entry of birds and insects
(Hilmarsson, 2008).
Along with many examples of double skin facades in Europe, particularly a notable
local example in Canada is at the Center for Cellular and Biomolecular Research at the
University of Toronto. In the double skin facade in this building, the air intakes and
outlets occur near the floor and ceiling of each floor, respectively, but to prevent
exhaust air from one floor entering the intake of the floor above, these can be
staggered from one floor to the next (Harvey, 2006, Section 3.4.1).
iii. Trickle vent – It is a very small opening in a window or other building envelope
component to allow small amounts of (passive) ventilation when major elements of
design like windows, doors are otherwise closed. Trickle vents are used extensively in
UK and Europe and are integrated into window frames to provide minimum
ventilation requirements for naturally ventilated spaces.
2. Mechanical ventilation – For buildings without operable windows, ventilation is
accomplished by mechanical means. A mechanical ventilation system will need to draw
in outdoor air, deliver it and remove stale air to make room for more fresh air. As part of
the mechanical ventilation system, there will need to be openings for both the
introduction of outdoor air and elimination of stale air. There also needs to be a driving
force – a pressure differential – to achieve the desired air movement. The air will move
as a result of pressure difference created both by the operation of the fans and by the
action of wind or temperature difference between the indoors and the outdoors.
31
i. Constant or variable – In this system, as the name suggests, constant or variable
amount of air is moved (as per a fixed schedule) to provide the required
ventilation.
ii. Mixing or Displacement – In a conventional Variable Air Volume (VAV) mixing
ventilation (MV) system, the air typically enters a room through an air inlet in
one part of the ceiling and returns through a vent elsewhere in the ceiling.
Mixing of fresh air and stale air existing in room is believed to provide the
required fresh air to the occupants. An alternative is displacement ventilation
(DV), in which a gentle flow of fresh air is introduced from many or a few
openings in the floor, or from long diffusers at the base of the walls. The air is
supplied at a temperature of 15-18 ˚C, spreads laterally, gets heated by heat
sources within the room while continuously rising and displacing the pre-existing
air. This provides superior quality air, but with less air flow than in a conventional
ventilation system.
iii. Demand controlled ventilation (DCV) – The ventilation rate should be varied
according to the need. One way of doing this is to apply a schedule for varying
the rate of ventilation, which is a fixed and inflexible schedule so it surely cuts
down on the energy as compared to the constant flow, but does not represent
the actual demand for ventilation, which might vary. The ventilation rate should
change with the changing occupancy of the building, rather than run at a fixed
rate based on maximum occupancy. Even in an all-air cooling system, it can be
advantageous to vary the ventilation rate or the ratio of outdoor to re-circulated
air, based on the ventilation requirement. This is referred to as demand-
controlled ventilation. DCV generally makes use of CO2 sensors to determine the
required ventilation rate in a given space, with CO2 used as a proxy for over-all
air quality and hence of the need for ventilation.
DCV can also be coupled with night-time passive or mechanical ventilation.
Where the day-night temperature variation is at least 5 K (preferably 10 K or
more) and peak outdoor temperatures are too warm for daytime ventilation
32
beyond the minimum air-quality needs, cool night air can be mechanically forced
through hollow-core ceilings, between double-skin walls, or through the
occupied space to cool the building prior to next day. The diurnal temperature
range is largest in regions having hot dry climates and thus, this technique is
most effective in such regions.
3. Hybrid - Another approach to ventilation is hybrid ventilation systems. These are the
systems that primarily rely on wind and buoyancy to provide adequate ventilation, with
assistance from only fans as needed. The common design elements in such systems
include:
Underground ducts, culverts, or plenums to pre-condition the supply air;
Operable windows and/or ventilation grills, which may be automatically
controlled;
Automatically controlled shading devices;
Solar chimneys or atria, possibly with backup fans;
Temperature and/or CO2 sensors.
Hybrid ventilation systems refer to demand controlled natural ventilation systems,
wherein advanced electronic control is applied in order to compensate during certain
periods of time the lack of sufficient pressure differences, fan assisted systems are used.
The buildings with hybrid ventilation system usually have good thermal design and
thermal mass, possibly with intensive night-time ventilation in order to limit day time
temperatures. The choice of energy-efficient fan systems (whether for night ventilation
or for daytime backup) matters as much or more as the use of passive ventilation. The
concept used for hybrid ventilation system is described in the figure below (Wouters et
al, 2000).
33
Figure 3.7 Hybrid ventilation concept graphic
The Commerzbank in Frankfurt (Germany), the Inland Revenue building in Nottingham
(UK), the New Parliament building in London (UK) and the Millenium Dome in London
(UK) are some examples of hybrid ventilation.
3.8.4 Production of Heat / coldness
1. Central Chiller - Air conditioning in commercial buildings can be accomplished by using
central chillers, which produce cold water that is distributed to radiators throughout the
building or to the cooling coils in the air handling system to distribute coldness. Central
chillers can use reciprocating, rotary or centrifugal compressors. The chiller efficiency
Hybrid Ventilation Concepts
Heat Recovery, Air
Cleaning
Demand controlled
natural ventilation
Low pressure
mechanical ventilation
Self regulating supply
and exhaust grills
Supply and exhaust grills
Openable
windows
Air infiltration
through cracks
Demand controlled
ventilation system
Constant air flow
mechanical ventilation
Natural Ventilation Mechanical Ventilation
34
largely depends on its part-load performance. The Coefficient of Performance (COP) of
the chiller depends on compressor speed. If the speed at which compressor runs
remains fixed, no matter what the cooling load is, it is called a fixed speed compressor
motor. The COP of fixed-speed chillers falls continuously with the decreasing load,
dropping to less than 20 percent of the full load COP at 20 percent of full load. A much
more efficient alternative, which should be used, is Variable Speed Drive (VSD)
compressor motor. This allows the compressor speed to decrease as the load decreases,
thus using only as much energy as is required to meet the cooling load.
2. Packaged Rooftop AC is another way of accomplishing air conditioning in commercial
buildings. These use a reciprocating compressor. The condenser is cooled by blowing
ambient air. The COP is based on the energy used by the compressor and the fan.
3. Boilers/Furnaces are conventional ways of producing on-site heat and/or hot water to
be supplied to the building. They are, generally, run on natural gas. The conventional
furnaces or boilers have typical efficiency of 60-70 percent. An energy efficient
alternative is a condensing unit with 90 percent or better efficiency, that can provide
both heat and hot water. This can provide 20-30 percent saving in fuel use.
4. District cooling/heating refers to centralised production of heat or chilled water using
electric chillers, which can be supplied to district network. A district heating system can
utilize waste heat due to cogeneration or it may distribute heat that is produced
centrally and separately from the generation of electricity. There can be, however,
substantial efficiency gains through centralised production of heat, compared to the use
of on-site boilers or furnaces, even in the absence of cogeneration and in spite of
distribution losses.
As with district heating/cooling, there can be efficiency gains with centralised
production of chilled/hot water, as compared to on-site production, because of
economics of scale. Further, the centralised systems can make it easier to shift to
renewable energy for heating and cooling.
5. Dehumidification and cooling using desiccants – Increasing the insulation of the building
envelope, adding shading, and reducing internal heat gain, reduce the sensible cooling
35
load, while having little effect on latent cooling load (dehumidification) (although
reduced air infiltration will reduce the latent cooling load), thereby making it difficult to
achieve adequate dehumidification with conventional cooling equipments. Larger
cooling coils permit higher evaporator temperatures for the same sensible cooling load,
thereby increasing chiller efficiency, but at the expense of reduced dehumidification
capability. An alternative is to overcool the air in order to induce adequate
condensation, then reheat the air, but at the expense of greater energy use.
Dehumidification without overcooling can be done using desiccants that directly absorb
moisture from the air and are regenerated using waste heat or solar heat. This allows
one to decouple the cooling and dehumidification functions. This is particularly
advantageous, when dehumidification requirements are large. All desiccant
dehumidification systems accomplish dehumidification without saturation, using heat as
an input, to regenerate the desiccant. A solid desiccant dehumidifier is a wheel rotating
at 10-60 rpm and packed with porous solid desiccant. The air to be dehumidified flows
through a portion of the wheel and moisture is absorbed. The wheel then rotates into
an air stream that has been heated in order to regenerate the desiccant by driving
moisture from the desiccant. Net cooling is achieved by precooling a secondary air flow
evaporatively and using it to cool the process airflow with a heat exchanger, and/or by
direct evaporative cooling of the process airflow, if the resulting humidity is acceptable.
This requires over-drying the process air.
6. Direct use of cooling tower water – The cooling tower cools the water that is used to
cool the chillers, through evaporation, to within a few Kelvin of the wet-bulb
temperature (Twb). If the cooling tower water becomes sufficiently cold as compared to
the outside air temperature and cooling load decreases, it could be used to directly
serve the cooling load, allowing the energy intensive compressor to be turned off.
Pumps are still required to circulate the cooling water and chilled water. The operation
of cooling water in this case is referred to as a water side economizer. The operation is
referred to as free cooling. This is particularly feasible in radiant chilled ceiling, in which
36
the temperature at which the chilled water needs to be supplied at a relatively higher
temperature (16-18 ˚C, vs 6-8 ˚C is common now in new hydronic cooling systems).
3.8.5 Distribution of Heat/coldness
1. Fan coil unit (FCU) – A fan coil unit is a simple device consisting of a heating or cooling
coil and fan. Typically a fan coil unit is not connected to ductwork, but is used to control
the temperature in the space where it is installed, or serve multiple spaces. It is
controlled either by a manual on/off switch, or by a thermostat.
2. Air Handling Unit (AHU)- An air handler is a device, used to condition and circulate air,
as a part of the HVAC system. An air handler usually consists of a large metal box
containing a blower, heating or cooling elements, filter racks or chambers, sound
attenuators, and dampers. Air handlers usually connect to ductwork that distributes the
conditioned air through the building and returns it to the AHU. Sometimes, AHUs
discharge (supply) and admit (return) air, directly to and from the space served without
ductwork.
Small air handlers, for local use, are called terminal units, and may only include an air
filter, coil, and blower; these simple terminal units are called blower coils or fan coil
units. A larger air handler that conditions 100% outside air, and no re-circulated air, is
known as a makeup air unit (MAU). An air handler, designed for outdoor use, typically
placed on roofs, is known as a packaged unit (PU) or rooftop unit (RTU).
3. Radiators - Radiators are heat exchangers used to transfer thermal energy from one
medium to another, for the purpose of cooling and heating. Baseboard heaters are, a
common form of radiators, used widely in commercial buildings.
4. Radiant ceiling- It is an energy efficient alternative to the above distribution systems.
This refers to hydronic cooling/heating by circulating chilled/hot water through the floor
or ceiling, thus causing radiative cooling/heating in the space. This has specific
advantages. The biggest advantage is that the water which is supplied doesn’t need to
be as cold in summers and as hot in winters, as compared to that used in all air HVAC
systems using ducts and radiators. This results in huge energy savings.
37
3.8.6 Heat recovery
In completely air tight buildings, fresh air needs to be provided by a mechanical ventilation
system when the windows are closed. The amount of fresh air that needs to be provided in this
case would be substantially less than the uncontrolled ventilation in leaky, poorly built
buildings. Further, a portion of the heat in the outgoing exhaust air, can be used to partially
heat the cold incoming air using an air-to-air heat exchanger (to form a heat recovery ventilator
- HRV). HRVs reduce peak heating and cooling loads, allowing downsizing of heating and cooling
equipment.
The heat exchangers belong to two basic categories: flat plate and thermal wheel. Flat plate
heat exchangers can be of the counter-flow or cross-flow type. Counter flow heat exchangers
are more effective than cross flow exchangers, but they require larger fans. A thermal wheel
consists of a wheel that rotates through the incoming and outgoing air streams. It can transfer
both, heat and moisture. These wheels can have desiccants, which dehumidifies and heats the
supplies and gets regenerated by the return air, which gets cooled and humidified. Studies
show that this type of system can deliver/supply air at much lower dew point temperature as
compared to that in conventional system with a marginal penalty on COP. Its performance is
better than a typical reheat system that provides the same low humidity levels (Subramanyam
et al, 2004).
3.9 Domestic hot water
The need to drain hot-water pipes of cold water when hot water is called for after a long period
of non-use is a source of wastage of water. This is done by opening the hot water tap until hot
water arrives at the faucet. The volume of hot water wasted is about twice as large as the
volume of cold water in the pipes that needs to be displaced, because the pipes themselves are
warmed up as the hot water flow begins, and this roughly doubles the waiting time. The waiting
time will be longer the greater the distance from the hot water heater to the faucet and the
slower the flow rate, while the amount of water wasted will be greater the greater the distance
between the heater and the faucet and the greater the diameter of the pipe.
38
An energy and water efficient alternative to the conventional method of circulating hot water is
a well-insulated recirculation loop (RL) that is periodically primed with hot water. RL, in which
hot water is continuously pumped through a loop and back to the hot-water tank, are
commonly used in commercial buildings. In this way, hot water is instantly available to hot-
water fixtures that are attached to the loop through short side branches. Water in a 2 cm pipe
that is insulated to RSI 0.7-0.9 (R 4-5) remains at above 40˚ C (a typical minimum required DHW
temperature) for 45-50 minutes once heated to 50˚ C. When the temperature drops to 40˚ C, a
temperature sensor activates a pump that circulates water for 30 seconds, restoring the
temperature of water in the RL to 50˚ C. Relative to the standard system, the primed RL reduces
total water use by 20.6 percent and heating energy use by 19 percent (Harvey, 2006, Section
8.2).
3.10 Lighting
The lighting system provides many opportunities for cost effective energy savings with little or
no inconvenience. Lighting improvement can safely be considered as a ‘low hanging fruit’ while
improving the energy efficiency of a building. In many cases, lighting can be improved and
operation costs can be reduced at the same time. Lighting accounts for a large part of the
energy bill in most commercial businesses, ranging from 30-70%. Thus, lighting improvements
are excellent investments. Some options for energy efficient lighting are detailed out below -
1. All electric – It is one of the ways of providing lighting in a building. A lot of commercial
buildings rely on providing the entire lighting requirement of the building by electric lighting
only. Various types of electric lamps used to provide electricity, include incandescent lamp,
halogen lamp, halogen infrared-reflecting (HIR) lamp, fluorescent lamp, compact fluorescent
lamp (CFL), electrode-less lamp, high intensity discharge (HID) lamp, ceramic metal halide
(CMH) lamp, Light-emitting diode (LED) and electro-luminescent (EL) lamp.
2. Daylighting – A better alternative to using only electric lighting in buildings is to allow as
much daylight as possible to enter the building in order to save on electricity. (Although
39
daylighting is advocated here as energy-saving measure, it may be pointed out that there are
also psychological, health and productivity-related benefits of daylighting over electric lighting.)
Techniques for maximizing the use of daylighting can start at the basic designing stage by the
architect. It starts from choosing the building form to window size, shape and position. This can
be followed by having atria or skylights, or various kinds of roof structures in order to allow for
maximized daylighting. Other daylighting strategies include, having light shelves, light-directing
louvers, automatic venetian blinds, light pipes, prismatic panels, laser-cut panels, light-guiding
shades, sun-directing glass and many more (Harvey, 2006,Section 9.3 ).
3. Control system – In order for daylighting to save energy, it has to be possible to reduce the
output of the electrical lighting system so as to provide just the required total light. This, in
turn, requires photo sensors and dimmable lighting. Inasmuch as clear windows will provide
more light than needed at times, causing overheating and discomfort and/or an increase in the
cooling load, full optimisation of the daylighting system also requires some form of
automatically adjustable shading system, such as motorized roller blades, venetian blinds or
louvers (Vine et al, 1998). Current state-of-the-art, commercially available daylighting and
shading control systems involve components like a central computer connected to various
sensors and controls and to the building energy management system; automatic dimmable
lighting controls; a manual override via remote control; schedules for occupancy; an automated
shading system; dimmable ballasts that enable reconfiguration of the dimming zones in the
software, and more.
4. Task/ambient lighting - Not all tasks require the same amount of light. Therefore, in spaces
such as offices, in order to save energy use, relatively low background lighting can be provided
with local levels of greater illumination at individual workstations. This strategy is referred to as
task/ambient lighting. Not only can this alone cut lighting energy use in half, but individual
control over personal lighting levels is possible.
40
3.11 Energy use savings in various buildings across the globe
Several case studies have revealed that through implementation of improved design process
and efficient planning, which involves the architect, engineers and energy analysts working
closely with each other achieves drastic energy saving. Use of building simulation tools has
played a huge role in assisting the design of energy efficient buildings. Harvey (2006, Section
13.3) has published a summary on commercial buildings from around the world that have
achieved energy savings of 45-85% compared to typical new buildings in each region. Based on
these experiences, the following conclusions can be drawn:
Savings of 35-50% can be achieved (as compared to the ASHRAE 90.1-1999 standard)
with only a better design process using conventional technologies at no or little
additional upfront cost.
Substantially larger energy savings (75-80%) can be achieved by combining a holistic,
systems-oriented design process with advanced technologies and less conventional
approaches to meeting the energy building loads.
41
CHAPTER 4
THE CASE STUDY
4.1 The Building
Sheridian Business Plaza (Figure 4.1) is a 1806 m2 (floor area) shopping plaza, located in
Brampton, ON. It has two floors; the first floor consists of stores and eatery places and the
second floor has some offices. There is no basement in the building.
Figure 4.1 Graphical representation of the building (Source: www.gdnlawyers.com)
42
Figure 4.2 Geometrical representation of the building.
Figure 4.3 Floor Plan of First Floor (with units as zones).
43
Figure 4.4 Floor Plan of Second Floor (with units as zones).
4.2 Climate of Southern Ontario
The climate in Toronto is marked by cold winters and relatively warm summers. According to
the Environment Canada (2008) historical data, the annual average outdoor temperature is
7.5oC and the warmest month is typically July with mean temperature of 20.8oC. The coldest
months are January and February, with mean temperatures -6.3oC and -5.4oC respectively.
Heating Degree Days (HDD) is approximately 4000 Kday. Toronto is located at the south-eastern
part of Ontario, and is heating dominated. According to the Natural Resources of Canada
(2006), space heating accounts for 55.3% of the total energy requirement in buildings in
Ontario, whereas space cooling accounts for merely 4.4%.
4.3 As-is case design parameters
This section describes the design parameters of the building in question. The details include the
envelope construction, lighting, equipment and HVAC design.
4.3.1 Envelope
The envelope elements include walls, roof, floor, and fenestration. The details of each of these
are described starting with wall construction.
44
4.3.1.1 External Wall construction
The different layers, from inside to outside, and their relative thicknesses are graphically
represented in Figure 4.5.
Figure 4.5 Section of the external wall of the building.
The materials and properties of different layers of external walls of the building in question are
given in Table 4.1.
45
Layer Material Thickness
(m)
Density
(kg/m3)
Specific Heat
(J/kg·K)
Thermal
Conductance
(W/m·K)
1 Face Brick 0.1016 2800 896.0 0.770
2 Air Space (at 0˚) .0508 1.293 1.005 .0243
3 Exterior Grade Drywall 0.0158 900.0 1000.0 .250
4 Batt Insulation and
metal studs at every
0.45 m
0.1524 12.0 840.0 0.040
5 6 MIL Poly Vap Bar 0.1524 980.0 1800.0 0.50
6 Drywall 0.0158 900.0 1000.0 .250
Table 4.1 Properties of materials consisting of various layers of existing external wall
construction (Reference: The building drawings)
4.3.1.2 Roof Construction
The materials and properties of different layers of the Roof, starting from outside to inside, are
given below in Table 4.2.
46
Layer Material Thickness
(m)
Density
(kg/m3)
Specific Heat
(J/kg·K)
Thermal
Conductance
(W/m·K)
1 Gravel Bedding 0.05 2100.0 650.0 1.4
2 4 ply Built up Felts 0.025 1100.0 1000.0 0.23
3 (R-20) Rigid Insulation 0.1016 12.0 840.0 0.04
4 Vapour Barrier 0.0130 980.0 1800.0 0.5
5 Steel Deck and
Structure
Table 4.2 Properties of materials consisting of various layers of existing Roof construction.
4.3.1.3 Floor Construction (Slab on grade)
The materials and properties of different layers of the Slab on grade, from ground to inside, are
given below in Table 4.3.
Layer Material Thickness
(m)
Density
(kg/m3)
Specific Heat
(J/kg·K)
Thermal
Conductance
(W/m·K)
1 Gravel bedding 0.0508 2100.0 650.0 1.4
2 Vapour Barrier 0.0130 980.0 1800.0 0.5
3 Cast Concrete 0.1016 2000.00 1000.0 1.13
Table 4.3 Properties of materials consisting of various layers of existing Floor construction.
47
4.3.1.4 Fenestration
Windows – All the windows are argon gas filled, double glazed units, consisting of an outer
pane of 6 mm thick clear glass and an inner pane of 4 mm thick glass. Windows are framed with
aluminum. According to the designer’s specifications, all windows have a solar heat gain
coefficient (SHGC) of 0.44 and a center of glass U-value of 1.97 W/m2K. The overall U-value of
the window, considering the frame would be 3.71 W/m2K. Light transmission is set as 0.9 for all
windows. The window-to-wall ratio is 30%.
Doors – There are two kinds of doors for exit from and entry to the building (on the first floor).
One type is metal, located on the back of the building and used mainly by the staff in the stores.
The U value of the metal doors is 0.51 W/m2-K. The other type of door is glass, used for entry or
exit by the customers. The glass doors have a U vale of 2.27 W/m2-K and SHGC of 0.35.
4.3.1.5 Thermal resistance of Envelope
The overall heat flow through the building envelope depends on the overall thermal resistance
of the envelope, which can be calculated area weighting of U-values of different elements. The
overall resistance of the existing building has been calculated in Table 4.4.
Element Area (m2) U-value
(W/m2K)
Thermal
Resistance,
RSI (m2K/W)
R-value
(Imperial)
External Wall
considering
thermal bridges
892.88 0.33 3 17
Roof 1068.16 0.25 4 22.71
Floor 1786.8311 0.55 1.82 10.33
Windows 263.13 3.71 0.27 1.53
48
Metal Doors 24.39 0.51 1.96 11.13
Glass Doors 20.75 2.5 0.4 2.27
Total (overall) 6012.07 0.51 1.96 11
Table 4.4 Thermal Resistance of various elements of the existing envelope.
As calculated in the above table, the total surface Area of the envelope is 6012 m2, the overall
U-value of the envelope is 0.51 W/m2K and the overall Resistance is 1.81 m2K/W or R 11. This,
however, does not consider the thermal bridges at the metal studs between which insulation is
placed. Below is shown a simple calculation considering the existing wall construction. A typical
wall section is drawn and the effective U-value of the wall section has been calculated
considering fractional areas of metal studs and insulation and their U-values. Thermal
conductivities of metal studs and insulation are 15 W/m-K and 0.04 W/m-K respectively and
their fractional areas are 0.04 and 0.96 respectively.
From the above calculation we can clearly see that the U-value of insulation considerably
increases by insulation being in between metal studs. This is due to very less thermal resistance
of metal studs, as well as, them behaving like thermal bridges. Subsection 5.4 explains the
better ways of construction in order to avoid thermal bridges.
R3 R2
R1
11
R2 = 1/U2
U2 = AreaStud.U-ValueStud + AreaInsulation.U-ValueInsulation
=0.04*15 + 0.96*0.26
= 0.6 + 0.25
= 0.85 W/m2K
49
4.3.2 Occupancy, Lighting and Equipment
Zone Area Occupancy LPD (W) EPD (W)
First Floor -
Coffee House 101.40 0.046 12.92 43.06
Cofee Shop WR 5.69 0.037 10.76 4.89
Mech/Electrical 12.99 0.046 16.15 64.58
HallWay1 10.22 0.036 7.53 4.83
Optical Store 80.43 0.046 18.30 8.61
Optical Store WR 5.08 0.037 10.76 4.89
Food Store 1 85.28 0.046 18.30 32.29
FS1 WR 5.17 0.037 10.76 4.89
Subway 85.51 0.046 12.92 43.06
Subway WR 5.17 0.037 10.76 4.89
Salon 75.53 0.046 12.92 8.61
Salon WR 5.17 0.037 10.76 4.89
Hallway2 16.71 0.036 7.53 4.83
Walk-in-Clinic 78.54 0.046 12.92 16.15
WIC WR 5.17 0.037 10.76 4.89
Pharmacy 100.61 0.046 12.92 8.61
Pharmacy WR 5.17 0.037 10.76 4.89
Conv. Store1 103.90 0.046 18.30 10.76
CS1 WR 5.17 0.037 10.76 4.89
CS 2 113.94 0.046 18.30 10.76
Hallway 3 11.21 0.037 7.53 4.83
Restaurant 104.04 0.046 16.15 43.06
Second Floor - Office 1 197.36 0.054 15.07 8.61
Office 1 WR 2.66 0.019 10.76 4.89
Office 2 78.81 0.054 15.07 8.61
Office 2 WR 2.66 0.019 10.76 4.89
Office 3 173.71 0.054 15.07 8.61
Office 4 157.18 0.054 15.07 8.61
Office 4 WR 5.69 0.018 10.76 4.89
Office 5 82.47 0.054 15.07 8.61
Office 5 WR 2.66 0.019 10.76 4.89
Hallway 21 14.10 0.018 7.53 4.83
50
Hallway 22 55.05 0.018 7.53 4.83
Hallway 23 11.79 0.018 7.53 4.83
Table 4.5 Area, occupancy, Lighting Power Densities (LPDs) and Equipment Power Densities
(EPDs) of all the zones.
4.3.3 Infiltration
In the absence of physical testing, it is rather difficult to decide on an infiltration level for a
building. There is also very little information available on natural air exchange in commercial
buildings. But whatever little there is suggests a range of 0.1 – 0.6 ACH at normal conditions.
(Harvey, 2006, Section 3.7.1). For the building in question, considering the envelope design, lack
of vestibules in the retail units, as well as the workmanship and construction practices, the rate
of infiltration can be assumed as 0.4 ACH. After obtaining and analysing the results, it is
observed that infiltration is a vital factor affecting the heating energy use for the building, so it
is critical to achieve an envelope with minimum possible unwanted air flow through it.
4.3.4 HVAC system
The HVAC system for the building is two-pipe DX Packaged Single Zone with Rooftop units. The
rooftop units are gas heat and electric cool with COP of 0.8. The heating set point and setback
temperature are set as 23 ˚C and 20 ˚C, respectively. Cooling set point and setback temperature
are set as 24 ˚C and 27 ˚C, respectively. There are 0.6 m X 0.6 m supply air diffusers and ceiling
plenum is used as return air plenum. Return air grill is placed into drop ceiling. There is Heat
Recovery system installed, which recovers around 30% of the heat from the mechanical HVAC
system.
4.3.5 Schedules
There are various schedules created to control the simulation of building’s mechanical
functioning. These schedules are included in Appendix B. The names of various Annual, Weekly
and Daily schedules are as follows -
1. Annual schedules – Occupancy, Institutional Light, Fan, Cool and Heat
2. Weekly schedules – Occupancy, Institutional Light, Equipment, Cool, Heat, Fan and Cook
51
3. Daily schedules – Occupancy Week Day, Occupancy Week End, Institutional Light WD,
Institutional Light WE, Equipment WD, Equipment WE, Cook WD, Cook WE, Cool WE,
Cool WD, Heat WE, Heat WD and Fan
4.4 As-is Case Results
A model of the As-is-case building was created in eQUEST by feeding the geometry of the
building in question and the design details as described above and the building was simulated.
The results of the simulation show that the Energy Use Index (EUI) is 447 kWh/m2/yr and the
Heating Use Index (HUI) is 320 kWh/m2/yr. The simulation results are presented in graphical
form below. Figure 4.6 shows the breakdown of overall electric consumption through the year
by different factors. Figure 4.7 shows the breakdown of overall gas consumption through the
year by space heating and domestic hot water. Figures 4.8 and 4.8 show the breakdown of
annual electric and gas consumption respectively and Figure 4.9 shows the cumulative energy
use (gas and electric) through the year by various factors.
Figure 4.6 The overall electric consumption in kWh/m2/yr for the as-is case.
0
2
4
6
8
10
12
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Area Lights
Task Lights
Misc. Equip.
Ext. Usage
Pumps & Aux.
Vent. Fans
Hot Water
HP Supp.
Space Heat
Refrigeration
Heat Reject.
Space Cool
52
Figure 4.7 The overall gas consumption in kWh/m2/yr for the as-is case.
Figure 4.8 Percentage breakdown of electricity use for the as-is case.
0
5
10
15
20
25
30
35
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Hot Water
HP Supp.
Space Heat
Refrigeration
Heat Reject.
Space Cool
6 13
3
42
37
Space Cool
Vent. Fans
Pumps & Aux.
Misc. Equip.
Area Lights
53
Figure 4.9 Percentage breakdown of natural gas use for the as-is case.
Figure 4.10 Cumulative energy use in kWh/m2/yr throughout the year by various factors.
97.8
Space Heat
Hot Water
0
20
40
60
80
100
120
140
160
180
Space Cool Vent. Fans Pumps & Aux.
Misc. Equip.
Area Lights Space Heat Hot Water
7 15
3
47 41
172
4
54
4.5 Analysis of As-is Case Results
According to the simulation results, heating use of the building amounts to almost 60 percent
of the entire energy use. Thus, heating the building is the most energy intensive process and
should need maximum attention and work, in order to bring down the overall energy use
dramatically. The building uses a natural gas furnace to provide for heating and domestic hot
water, and out of this 98 percent of the gas is used for heating only 2 percent for domestic hot
water.
Looking at the electricity usage by different factors, the three keys areas, where electricity is
used, are miscellaneous equipment (16 percent) and area lights (14 percent). Less than 1
percent of the electricity is used for space cooling, which is justifiable by the climate of the
region. Space cooling is required mainly during the months of June, July and August.
From this, we can identify the key areas that need to be addressed, in order to reduce the EUI
of the building. These would be heating, equipment, lighting and ventilation fans. In the
following chapter, various models are presented that reflect the modifications done to the
building parameters and design, in order to cut down on the energy usage, and the results are
analysed.
The equipment energy use reduction depends only on using more energy efficient models and
does not have anything to do with building design. In this study, the equipment part of the
energy use of the building will not be worked on and it is left on the building owners to reduce
the equipment use and use of more energy efficient equipment to replace the existing ones.
4.6 Rough manual calculations to check the Heat load for the As-is-Case
Some calculations are done to cross check the heat load as achieved by the software. Heat loss
from a building is a difference of total heat loss from the building and total heat gain that
occurs in the building due to people, lights, equipments, appliances etc.
55
Total Heat loss can be categorized into –
i. Conduction heat loss – this is heat being lost by conduction through the envelope of the
building. Various elements of envelope through which heat loss occurs are walls, roof,
floor, windows etc. The more resistance the envelope, lesser the heat loss.
ii. Convective heat loss or heat loss due to air exchange – this is heat being lost through air
that is being exchanged between the envelope and outside environment. This can be of
two types:
a. Uncontrolled air exchange or infiltration – Uncontrolled air exchanged occurs
through the leaks or cracks in the building envelope. This is responsible for large
heat loss in a lot of buildings. There is no way this heat loss can be recovered or
stopped other than building tighter envelopes.
b. Controlled air exchange or mechanical ventilation – in absence of natural ventilation,
mechanical ventilation has to be provided. This is bringing fresh air from outside and
supplying it to the indoors, some stale air is sent to outdoors. This air exchange is
also responsible for heat loss but it is possible to recover around 70-80 % of this heat
loss using Heat Recovery.
The total heat gain in the building (due to people, equipments, lights, appliances etc.) is
subtracted from the total Heat loss due to all the above categories to achieve the net heat loss
from the building. Table 4.6 shows the detailed manual calculation of heat loss for the As-is
case and Table 4.7 shows the manual heat requirement and heat load calculations for all the
cases. The formulas used to do the calculations are given below –
Conduction heat loss (kWh/m2/yr) =
Heat Loss due to air exchange (kWh/m2/yr) =
[(ACH* Bldg. Volume (m3) * Specific Heat of air
(J/kg-K) * Air Density (kg/m3) * HDD * 24) /
3600000]
Building Area (m2)
[(Total Surface Area (m2) * Average U-Value (W/m2-K) *
HDD * 24)/1000]
Building Area (m2)
56
As-is Case
Conduction Heat Loss -
Building element Area U-value
(m2) (W/m2-K)
Window 308.27 3.0
Wall 584.61 0.33
Roof 1068.16 0.25
Floor 1786.83 0.55
Total or Average 3747.87 0.63
Approximate Conductive Heat Loss : 63.13 KWh/m2/yr
Heat Loss due to Uncontrolled air exchange -
Uncontrolled air changes per hour 0.4
Approximate Heat Loss 55.70 KWh /m2/yr
Heat Loss due to Controlled air exchange -
Ventilation rate 1.76 (m3/second)
Controlled Air changes per hour 1.7 ACH
Heat Loss 236.70 KWh /m2/yr
Heat Recovery (%) 30%
Total Heat loss due to controlled air exchange 165.69 KWh /m2/yr
Total Heat loss due to conduction and air exchange 284.52 KWh /m2/yr
Heat gain -
People 15 KWh /m2/yr
Lights 41 KWh /m2/yr
Equipments 46 KWh /m2/yr
Total Heat Gain 102 KWh /m2/yr
Net heat Load 182.52 KWh /m2/yr
Total Heat Loss as per eQUEST 171.55 KWh /m2/yr
Table 4.6 Rough manual calculation for total heat loss for the As-is-case
57
Categories AIC WF WI ENV INF LGT HR HVAC
Conduction Heat Loss -
Wall 24.66 9.28 1.64 1.64 1.64 1.64 1.64 1.64
Window 5.14 6.83 6.83 2.28 2.28 2.28 2.28 2.28
Floor 7.12 7.12 7.12 3.7 3.7 3.7 3.7 3.7
Ceiling 26.21 26.21 26.21 7.62 7.62 7.62 7.62 7.62
Total Conduction Heat Loss (KWh /m2/yr) 63.13 49.44 41.8 15.24 15.24 15.24 15.24 15.24
Uncontrolled ACH 0.4 0.4 0.4 0.4 0.1 0.1 0.1 0.1
Heat loss due to uncontrolled ACH (KWh /m2/yr) 55.7 55.7 55.7 55.7 13.92 13.92 13.92 13.92
Controlled ACH (Mechanical Ventilation) 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.4
Heat recovery 30% 30% 30% 30% 30% 30% 80% 80%
Heat loss due to controlled air exchange(KWh /m2/yr) 165.69 165.69 165.69 165.69 165.69 165.69 71.01 58.48
Total Heat Loss due to Air Exchange 221.39 221.39 221.39 221.39 179.61 179.61 84.93 72.4
Total Heat Loss (KWh /m2/yr) 284.52 270.83 263.19 236.63 194.85 194.85 100.17 87.64
Heat gain -
People 15 15 15 15 15 15 15 15
Equipments 41 41 41 41 41 41 41 41
Lights 46 46 46 46 46 14.5 14.5 14.5
Total Heat Gain (KWh /m2/yr) 102 102 102 102 102 70.5 70.5 70.5
Net Heat Load (Heat Loss-Heat Gain) (KWh /m2/yr) 182.52 168.83 161.19 134.63 92.85 124.35 29.67 17.14
Heating System efficiency 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.92
Total Heat Load (Net Heat Load/efficiency) (KWh /m2/yr) 228.15 211.04 201.49 168.29 116.06 155.44 37.09 18.63
Table 4.7 Manual heat requirement and heat load calculations for all (relevant) cases.
58
CHAPTER 5
MODIFICATIONS, RESULTS AND ANALYSIS
This chapter presents the results and analysis of all the cases that were simulated. After
simulating the as-is case, several modifications were made. These modifications represent the
best practice design and operations that should be used to achieve vastly reduced energy loads
for a building. Most of these modifications need to start at the design and planning stages of
any building. A few passive design changes are made in the beginning followed by envelope,
lighting, and mechanical systems modification, in that sequence. This particular sequence has
been decided because the simplest modifications have been made earlier followed by
complicated ones. The changed factors are described and results are analysed for each new
case. The results are presented in an incremental format, which means that the energy demand
variation caused by each modification is calculated on top of the previous model’s variation and
results of each model are compared with results of the as is case, as well as the previous case
that was modeled.
Table 5.1 presents the nomenclature followed to represent the various cases and the details of
the cases are given ahead in the text.
S.No. Name Description of case
1. AIC As-is-Case (existing building design)
2. OT Changed orientation
3. WF Changed window fraction
4. WS Added shading on windows
5. WI Windows of the building improved
6. ENV Improved walls, floor and roof
59
7. INF The improved Infiltration levels
8. LGT Lighting improved
9. HR Adding heat recovery in the exhaust
10. HVAC Improved HVAC system
Table 5.1 Nomenclature used to represent various cases
The first case, i.e. the As-is-case (AIC) has been described in detail in Chapter 4.
The next eight cases have been analysed in detail in this chapter. The improvements are
cumulative, in the order specified in Table 5.1. The simulation results for all the cases are
presented in graphical form below. Figure 5.1 represents the variation in the total energy
demand throughout the different cases. Figure 5.2 shows the variation in the heating demand,
Figures 5.3 and 5.4 show the variation in cooling demand and ventilation energy demand,
respectively.
Figure 5.1 Variation in the total energy demand (kWh/m2/yr)
0
50
100
150
200
250
300
AIC OT WF WS WI ENV INF LGT HR HVAC
288 287 279 283
233
192
156 148
139
114
60
Figure 5.2 Variation in heating energy demand (kWh/m2/yr)
Figure 5.3 Variation in cooling energy demand (kWh/m2/yr)
0
20
40
60
80
100
120
140
160
180
AIC OT WF WS WI ENV INF LGT HR HVAC
172 172 162
172
121
76
39
53
29
15
0
1
2
3
4
5
6
7
8
AIC OT WF WS WI ENV INF LGT HR HVAC
7
6 7
4 4
7
8
5
7
5
61
Figure 5.4 Variation in vent fan energy demand (kWh/m2/yr)
5.1 Orientation (OT)
The orientation of the building has been changed, so that the long axis aligns with the East-
West direction and the side with maximum glazing faces South. This allows for maximum
possible solar gain during winter months. This is purely an architectural decision and has to be
taken at the design phase. In eQUEST, this was achieved by setting the ‘azimuth’ of the building
as zero. Figure 5.5 is the snapshot of the eQUEST screen showing the orientation of the existing
building and Figure 5.6 is the snapshot of the eQUEST screen showing the changed orientation
of the building.
0
5
10
15
20
25
30
AIC OT WF WS WI ENV INF LGT HR HVAC
15 14 15
13 13 14
15
13
26
16
62
Figure 5.5 Original orientation of the building (snapshot of eQUEST screen)
Figure 5.6 Changed orientation (snapshot of eQUEST screen)
63
Analysis
As observed from Figures 5.1, 5.2 and 5.3, the overall energy demand decreases only by about
1%, which is a result of slight decrease in the cooling and vent fans energy demands.
Parameters, such as, building shape, form and orientation, are more significant for smaller
buildings and buildings with lower performance envelopes (section 3.1). But, changing the
orientation opens further possibilities of having increased glazing fraction on the south facing
side, which is explored in the next subsection (5.2).
5.2 Modified glazing fraction (WF)
The overall glazing fraction in the as-is case was 30 % and it has been modified to be 13.5 %.
The glazing fraction on the south facing wall has been increased from 28 % in the as-is case to
39 % and that on the north facing wall has been reduced from 20 % to 8 %. Even though
windows on the West wall bring a lot of glare and heat in the late evening hours, they could not
be avoided because the commercial unit on that end is a coffee shop and windows are required
for good views and sunlight.
Analysis
As observed from Figures 5.1, 5.2 and 5.3, by making the changes as mentioned in window
fraction, the cooling demand of the building increases by about 15 percent but the heating
demand decreases by about 6 percent. The overall energy demand of the building decreases by
about 3 percent because of the relative importance of heating and cooling energy
requirements. Heating energy requirement of the building is roughly 60 percent whereas
cooling energy is less than 1 percent of the entire energy demand in the As- is case.
The slight increase in cooling energy demand can be attributed to the absence of shading on
the increased fraction of south windows, due to which much of the heat gain is happening
during summer seasons.
The decrease in the heating energy demand is due to the increased glazing fraction on the
south side. The sun is lower and on the south side during most of the day time during winter,
64
thus, increasing the glazing fraction on the south side considerably increases the solar heat
gain.
5.3 Added shading on windows (WS)
The windows on the South side have been provided with overhangs that are at 90˚ to the wall
and 3 ft deep.
Analysis
As observed from Figures 5.1, 5.2 and 5.3, by adding the shading as mentioned on the south
windows, the cooling demand of the building decreases by about 60 percent but the heating
demand increases by about 2 percent. The overall energy demand of the building goes up
because of the relative importance of heating and cooling energy requirements, as explained
earlier (section 5.2). As observed in the sun path diagram for Brampton’s latitude (Fig 3.1), the
sun is higher in the sky during summer. Thus, by introducing the window shadings, the solar
heat gain during summer is reduced considerably and subsequently, the cooling energy
requirement decreases.
The increase in the heating load can be attributed to the blockage of some of the scattered
heat in winter season due to the shading now incorporated. Also, the true advantage of having
increased glazing on east side, in terms of solar gain, can be taken when we have higher
performance windows, which is explored in the next subsection.
5.4 Window improvement (WI)
The as-is building had double glazed argon windows with a glass U-value of 1.97 W/m2-K (see
section 3.3.1.4 for further details). As part of the modifications, Optiwin windows
(www.optiwin-usa.com), a German product manufactured for North American buildings was
chosen. The details of the particular window type selected are described in Table 5.2.
65
Glass
U-value (W/m2-K)
R-value
Frame
U-value (W/m2-K)
R-value
Overall
U-value (W/m2-K)
R-value
Glass SHGC
U- 0.53
R- 10.7
U- 0.73
R- 7.8
U- 0.68
R- 8.4
0.53
Table 5.2 Details of the windows chosen for modified building.
Along with choosing good windows, a shading schedule was designed for the entire year, which
had different weekly schedules for winter and summer. The schedule was designed for internal
blinds and it is open during the business hours in winter months to allow for maximum solar
gain and is closed during business hours in summer months to restrict solar heat gain during
summer. The details of the shading schedule are presented in Appendix with other schedules.
Proper installation of the windows is crucial to ensure that there are no thermal bridges in the
window and wall assembly. Section 3.4 explains the appropriate positioning of window frame
with respect to insulation in order to avoid thermal bridges.
Analysis
Since the results are observed in an incremental fashion, when compared to the previous case
(WS), a considerable reduction of 19 percent in the overall energy demand is noticed by
improving the performance of windows along with the above mentioned passive changes (as
observed from Figures 5.1, 5.2, 5.3 and 5.4). This can be attributed to the reduction in the
heating demand, that occurred by 30 percent. The heating load is clearly reduced due to lesser
heat loss through the windows due to their decreased glass and frame U-values and higher heat
gain due to increased solar heat gain coefficient.
Since the heating demand in our building is the most dominant load, it is sensible to opt for
windows with higher solar heat gain coefficient.
5.5 Envelope improvements (ENV)
The resistance of walls and the roof is increase from the as-is case from RSI-3, R-17 (U-Value =
0.33 W/m2-K) for walls and RSI-4, R-22 (U-Value = 0.25 W/m2-K) for roof to RSI-9, R-50 (U-Value
66
= 0.11 W/m2-K) and RSI-8, R-44 (U-Value = 0.13 W/m2-K). In order to upgrade the resistance
from R-17 to R-50, double framing with high density fibreglass batt insulation can be used.
The new floor resistance is upgraded from R-10 (U-value 0.55 W/m2-K) to RSI-6.25, R-35 (U-
value 0.16 W/m2-K), which would require adding 20 cm of fibreglass insulation in the floor
construction.
Along with the envelope elements such as walls, roof and floor, heat loss also occurs at the
corners, edges and junctions. These places where the heat flow through a building element is
disturbed, especially those where is it higher than in regular construction, are called thermal
bridges. In order to make a good thermal insulation effective, it is necessary to reduce the
thermal bridge effect. This can be achieved by appropriate placement of insulation and frames
as well as good workmanship. Careful site inspection and stringent quality control measures
play a huge role in assuring thermal bridge-free construction. Figures 5.7 and 5.8 illustrate the
appropriate construction practices that should be used to avoid thermal bridges. In both the
figures, the left part shows the placement of insulation and right part shows the heat through
the building element. In Figure 5.7 the placement of insulation is appropriate and thus, there
are no thermal bridges, whereas in 5.8, the placement of Insulation is improper and that leads
to enhanced heat flow through the building envelope.
Figure 5.7 Thermal-bridge-free
67
Figure 5.8 NOT thermal-bridge-free
Thermal bridges can be largely avoided by having insulation snugly held all around a building.
(www.europeanpassivehouses.org).
Figure 5.9 illustrates the envelope detail of best practices followed in Germany in order to
avoid thermal bridges. It can be noticed that the insulation in the facade and roof is on the
outer side of the envelope. Floor has insulation just under the finished floor tile and windows
are three pane windows.
Figure 5.9 Best practices of envelope construction
(Source: www.europeanpassivehouses.org).
68
Analysis
As observed from Figures 5.1, 5.2, 5.3and 5.4, the overall energy demand has decreased by
almost 33 percent by making some passive changes, improving the windows and improving the
thermal envelope. This reduction is largely due to the reduction in heating energy by 56 percent
as compared to the as is case and 37 percent as compared to the model with triple pane
window (as explained previous to this case). The decrease in heating energy happens because
of the large increase in thermal resistance of the building envelope, which includes walls, roof
as well as floor. Some heat loss also occurs from floor to the ground, which is why it is very
important to add insulation to floor of the building as well.
The cooling energy demand decreased by 42 percent by changing the orientation, altering
glazing fraction and adding shading. It increases by the same amount due to reduced heat loss
and gain through the envelope, which increases the heat to be removed from the building. The
absolute increase in cooling demand is, however, minimal as compared to the decrease in
heating demand, so we can ignore this change.
Along with having a building envelope with large thermal resistance, it is also very important to
have a very tight, leak or crack-free envelope. This is explored in the next section.
5.6 Infiltration (INF)
Infiltration refers to the heat loss through a building envelope due to uncontrolled air
movement (through cracks, leaks). An airtight building shell with controlled ventilation is a pre-
requisite for excellent energy performance in any Canadian building. The simulation tool
eQUEST allows entering the number of infiltration-caused air changes per hour at a reference
wind speed of 4.47 m/s. It has a correction for wind speed as shown in the following equation:
Infiltration in ACH = (AIR-CHANGES/HR) * (wind-speed)/(reference wind speed)
The air change rate of the building at a pressure difference of 50 Pa indicates the level of air
tightness. The as is case of the building was believed to have 0.4 ACH at regular conditions
(subsection 3.3.3). The modified ACH is 0.1. A factor of four reduction in the ACH is quite
achievable by flawless workmanship and installation techniques, which includes paying careful
69
attention to the design of junctions between elements to ensure continuity of the air barrier
and to minimizing the penetrations of the thermal envelope, whether by services or structure
or construction. This reduction in ACH is also inexpensive to achieve. Controlled mechanical
ventilation in order to provide the required fresh air with heat exchanger is additional to this air
exchange.
Analysis
As observed from Figures 5.1, 5.2, 5.3 and 5.4, the results of this simulation clearly suggest that
minimization of infiltration, or unwanted air exchange through the envelope, plays a huge role
in reducing the energy use by the building.
By making the above change in infiltration level, the overall energy demand decreases by 18
percent as compared to the previous case and now the results show a total reduction of 46
percent as compared to the as-is building.
The decrease in the total energy demand is due to the vast reduction in the heating energy
demand. The heating demand decreased by 50 percent as compared to the previous model
(with upgraded insulation) and by 86 percent as compared to the as-is model. The cooling
energy, however, increases by 12 percent and that is due to lesser heat loss through the
envelope during the cooling months as well as lesser cool air entering the envelope, which
would have helped in reducing the cooling load as well as the heat gain from inside the
envelope remains the same. But again, since the proportion of cooling energy is so small as
compared to the total energy demand, this increase can be ignored.
5.7 Lighting (LGT)
After largely reducing the energy demand by envelope upgrades, tightening the envelope and
other measures, lighting was explored. There are a few changes that have been made in the as-
is lighting design and they are as follows –
1. Daylighting in all the retail and office units is introduced. Daylight sensors are placed
near windows. Some of the units have one and some have two sensors, depending on
their geometry and window placement. The sensors dim the fixtures’ output in three
levels and eventually switch them off, depending on received daylight.
2. The overall LPDs (Lighting Power Densities) have been reduced by 10 percent.
70
3. Task lighting has been introduced in the office units on the second floor. The LPD of task
lighting is 10.76 W/m2 and a task lighting schedule has been assigned for the calculation
of the loads. (Refer to the Appendix for the details of task lighting schedule). The overall
LPDs of the office units have been reduced by 20 percent since task lighting is believed
to provide some of the required lighting intensity.
Analysis
By making the changes as described in subsection 5.6.1, the overall energy demand decreases
by 5 percent as compared to the previous case and by 49 percent as compared to the as is case.
This decrease is largely due to a 42 percent decrease in the energy demand for area lights. The
cooling energy demand also decreases by 37 percent, causing the vent fan energy demand to
decrease as well. This decrease happens because reduced lighting power densities produce
lesser heat to be removed during cooling months. At the same time, the heating load increases
by 26 percent as compared to the previous case due to lesser internal heat gain resulting from
reduced LPDs.
Challenge with eQUEST – While simulating changes in lighting, it was observed that we do not
have the choice of changing the type of lighting fixture to be used. The only way of improving
the lighting energy use is by reducing the Lighting Power Densities. Given an option, once can
choose better fixtures and ballasts
5.8 Heat Recovery (HR)
After making the changes in lighting, a more efficient heat recovery system was installed in the
building. The system consists of an enthalpy wheel to recover sensible and latent heat and has
high efficiency motors. An average of 1.6 litres/s/m3 of controlled mechanical ventilation is
provided by the HVAC system.
As shown in Figure 5.10, a heat recovery ventilator (HRV) consists of two separate air-handling
systems – one collects and exhausts stale indoor air, while the other draws in outdoor air and
distributes it throughout the building. At the core of an HRV is the heat transfer module. Both
the exhaust and outdoor air streams pass through the module and the heat from the exhaust
air is used to pre-heat the outdoor air stream. Only the heat is transferred; the two air streams
remain physically separate. Typically, an HRV is able to recover 70 to 80 percent of the heat
71
from the exhaust air and transfer it to the incoming air. This dramatically reduces the energy
needed to heat outdoor air to a comfortable temperature.
Figure 5.10 Schematic diagram of Heat Exchanger (Source: Wouters et al, 2000)
Analysis
Improving the efficiency of the heat recovery further reduces the heating demand by 45
percent as compared to the previous case and the overall energy demand by 6 percent (as
observed from Figures 5.1, 5.2, 5.3 and 5.4) as compared to the previous model and now our
total energy demand is 52 percent less than what it was in the as-is case.
Heat recovery suggests that so much of energy/heat can be re-circulated within the building
instead of letting it exit from the building along with stale indoor air.
The fan energy increases by 50 percent as compared to the previous case because now the fans
need more power in order to overcome the flow resistance of the heat exchanger.
72
Thus, as seen from these results, even without making any changes in the existing mechanical
system of the building, the overall energy demand has been reduced by 52 percent and the
heating demand, which had the biggest share of energy consumption, decreased by 83 percent.
This was accomplished by better orientation of the building, appropriate glazing fraction, more
resistance and tighter (resulting in minimal unwanted air exchange) building envelope and
addition of heat recovery in the mechanical system.
The next step is to make some changes in the HVAC system of the building and see how far that
can take us in achieving energy use reduction.
5.9 Mechanical systems (HVAC)
Challenge with eQUEST – Having reduced the heating load of the building to as low as possible,
it now needs to be met by the most efficient system. Radiant slab heating (and cooling) are the
most efficient way of distributing heat since this way heat is being distributed using water and
not air (subsection 3.9.5). Designing this system in eQUEST was a challenge faced. eQUEST is
not capable of modeling both heating and cooling using radiant slab in the same model.
Also, the most efficient way of providing ventilation is using Displacement Ventilation
(Subsection 3.8.3). eQUEST was found to be incapable of modeling a HVAC system with
Displacement Ventilation.
A representation of the above systems was created in eQUEST to achieve results, which can be
believed to be close to the actual results of this system The details of the changes made in the
HVAC system of the building are as follows –
1. Hydronic (water based) heating/- A natural gas boiler of 92% efficiency and a water
cooled chiller of 40 KW cooling capacity and Coefficient of Performance 5.8 were
installed.
2. Radiant slabs were used as the distribution system, in which case air was used only for
ventilation and the other two functions of HVAC systems (heating and cooling, including
production and distribution) were carried out by water.
The representation was created by attaching the boiler and the chiller to a hot water
and chilled water loop respectively and in the model the distribution happened through
these loops. Since in the original model ventilation fans were used to partly distribute
73
heat and coolness along with ventilation, the fan energy use was manually reduced to
only ventilation use. In this way, results of this model represented the system using
radiant slabs for distribution since that system will use fans only for ventilation.
3. The supply temperature for heating is set at 27˚ C and for cooling is set at 15˚ C. This
represents the temperatures required for radiant heating and cooling (subsection 3.9.5).
4. Demand Controlled ventilation was activated by installing the DCV zone sensors, which
are the CO2 sensors.
5. The average ventilation rate is 1.1 m3/s. This is reduced to represent displacement
ventilation, which cannot be possibly modelled in eQUEST.
Analysis
Implementation of the HVAC changes reduced the total energy use of the building by 18
percent as compared to the previous case and brought the total energy saving to 60 percent as
compared to the as-is case(as observed from Figures 5.1, 5.2, 5.3 and 5.4). The space heating
load came down to 15 KWh/m2/yr. The cooling load came down to 5 KWh/m2/yr and the vent
fans energy usage decreased by 38 percent as compared to the previous case since the fans are
now being used only for ventilation and not for heating or cooling.
Following the strategy worked out to achieve drastic energy saving, as mentioned in the
subsection 1.3, the efforts started with reducing the lighting, heating, and cooling energy
demand of the building by using daylighting strategies, passive design techniques, and building
a strong and tight envelope. After having reduced the energy requirement of the building by
using these strategies these loads were met by the most efficient ways. These are introducing
dimmable lighting, task lighting, using efficient chillers and boilers for hydronic heating and
cooling, distributing it using radiant slabs, dedicated outdoor air supply for ventilation, and
demand controlled ventilation using CO2 sensors.
The limitations of eQUEST did not allow modelling a radiant heating and cooling system so a
representation was produced (by turning the fan energy down to only ventilation). The actual
energy consumption values for heating, cooling and ventilation could slightly differ from the
values stated.
74
Among some important modifications that could not be modelled due to limitations of eQUEST
are displacement ventilation, passive ventilation using cool outdoor air, which could reduce
energy use further (refer subsection 3.9.3).
5.10 Primary Energy Use
Primary energy is the raw fuel that is burned to create heat and electricity, such as natural gas
(used to produce heat) or coal (used to produce electricity). Secondary energy is the energy
product (heat or electricity) created from raw fuel. Primary energy can also be called ‘source
energy’. There are two kinds of energy sources used for the building in question. One is Natural
gas, which is used as-is in the boilers. To calculate the primary energy use for Natural Gas, we
would need to go through the conversion process considering the efficiency of the boiler for
different cases. Thus, for a furnace of 80% efficiency, the energy used by natural gas will be
divided by 0.8 to achieve the primary energy use. The other energy source is electricity, which is
most likely produced in a coal-fired power plant. In order to calculate the primary energy for
the electricity use, we would need to go through the conversion process marking up for the
electrical power plant efficiency and transmission efficiency, which can be considered as 40%
for current plants and transmission infrastructure. Figure 5.11 shows the breakdown of primary
energy by electricity and that by natural gas used in each case and Figure 5.12 shows the total
(electric plus natural gas) primary energy use in each case.
75
Figure 5.11 Breakdown of primary energy by electricity and natural gas (KWh/m2/yr).
Figure 5.12 Total primary energy use (KWh/m2/yr).
0
50
100
150
200
250
300
350
AIC OT WF WS WI ENV INF LGT HR HVAC
282 279 282 270 271
279
308
229
259
239 219 219 207 219
156
100
53 71
41
20
Primary Electric
Primary NG
0
100
200
300
400
500
600
AIC OT WF WS WI ENV INF LGT HR HVAC
501 499 489 489
427
379 361
300 300
259
76
5.11 Financial Analysis
In order to justify the worth of modifications those have been suggested and simulated in the
current research work, a brief financial analysis is presented below.
The energy rates for commercial buildings in Brampton at present are as follows –
Electricity (Brampton Hydro) - $0.068 for the first 750 KWhand $0.079 for every KWhabove 750.
Since the consumption every month is way more than 750 kWh, we will assume the average
electricity rate per KWh as $0.076.
Natural Gas (Enbridge) - $00.13 per cubic meter for gas and $0.10 per cubic meter for delivery,
thus, the final rate is $0.23 per cubic meter.
Conversions –
1 m3 of Natural Gas = 37.5 MJ of energy
1 KWh= 3.6 MJ
1 KWh of energy would need (3.6/37.5)= 0.096 m3 of Natural Gas
5.11.1 Energy Cost
The energy costs of AIC (As is case) and HVAC case (final case with all improvements) are
calculated below as per the energy rates described above. The calculations are per square
meter per year of the floor area of the building in question.
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Case Electricity
Consumption
(kWh/m2/yr)
Electricity Cost
(As per 0.076
$ per kWh)
Natural Gas
Consumption
(kWh/m2/yr)
Volume of
Natural
gas used
(m3)
Natural
Gas cost
(As per
0.23 $ per
m3)
Total
Energy
Cost ($)
AIC 112.69 8.56 175.42 16.84 3.87 12.43
HVAC
(FINAL)
95.57 7.26 18.78 1.8 0.41 7.67
Savings ($) 4.76
Table 5.3 The total energy costs for the original and final cases per square meter per year of
the building area.
The overall energy saving after applying all the modifications is $4.76 m2/yr.
5.9.2 Net Present Value (NPV)
Net Present Value is the difference between the present value of an investment’s future net
cash flows and the initial investment. If the NPV is zero, the project would equate to investing
the same amount of dollars at the desired rate (Barney et al, 2008). In the current research
work, it would be important to learn the present value of the energy savings in dollars so that
we can compare it with the extra construction cost that goes in making the modified design and
judge if it really is worth investing that extra amount of money or not. The average construction
cost, as advised by the associated engineers, for the type of construction of the building in
question, is $1720 per square meter. The Present Value of 20 years of annual savings per
square meter is calculated for various inflation-adjusted annual rates considering increase in
energy prices.
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Considering -
P = Present value of annual savings
A = Annual savings ($ 4.76 per m2/yr of floor area)
i = Rate of inflation
n = Number of years (considered as 20)
The formula for calculating the present value of annual savings –
P = A [ {(1+i)n – 1} / {i(1+i)n} ] .............................(5.1)
(Source: Barney et al, 2008)
Table 5.4 shows the calculation of the Net Present Value of the annual energy savings per
square meter per year of the floor area of the building when the savings are calculated for a
period of 20 years. The NPV has been calculated for 3, 4 and 5 percent rate of inflation. The
inflation rate in the last decade has fluctuated between 1.1 % to 3.7 % so the numbers are
chosen considering the past rates and being conservative that it may even increase in the
coming two decades.
Rate of inflation
(%)
Calculation of Present value as per (5.1) Present Value
($)
3 4.76 [ {(1+0.03)20-1} / {0.03(1+0.03)20} ] 71.047
4 4.76 [ {(1+0.04)20-1} / {0.04(1+0.04)20} ] 64.66
5 4.76 [ {(1+0.05)20-1} / {0.05(1+0.05)20} ] 59.50
Table 5.4 The Net Present Value of the annual savings per square meter per year of the floor
area for various rates of inflation.
This amount (the calculated NPV) is the money that can be safely invested into a modified
construction. It should be noted here that the overall energy use reduction is not proportional
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to the energy cost reduction. This is because in the modified design, most of the energy loads
are being met by electricity and natural gas has very limited use and electricity is still about
three times more expensive than natural gas. The reason for meeting most of the energy load
by electricity is that intention is to reduce and ultimately stop the use of fossil fuels and meet
the entire energy load by electricity, which should be provided by electricity generated from
renewable sources like solar, wind, geothermal, hydro among others.
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CHAPTER 6
CONCLUSIONS
6.1 Challenges of eQUEST
This research analyses the building energy simulation tool eQUEST, that uses DOE-2 as its
simulation engine. The user interface for eQUEST is currently more developed than some other
powerful simulation tools. The user-friendly, mature and comprehensive user interface of
eQUEST makes it widely used in the industry even though the tool has some challenges, which
are not there in tools like EnergyPlus, IES <VE>, ESP-r or Ecotect. Some of the challenges of
eQUEST, as analysed from Crawley, 2005 and observed during simulating the case study for this
research work, are noted below. The softwares that work well with these challenge areas of
eQUEST are also mentioned.
1. eQUEST is not equipped to simulate Human Thermal Comfort (refer to definitions),
which is an important piece of information in order to design an energy efficient HVAC
system. Other tools like BLAST, EnergyPlus and IES (VE) are well equipped to do this.
2. Combined building envelope heat and mass transfer and interior surface convection
(dependent on temperature/air flow/CFD based surface heat coefficient) are further
processed that eQUEST is not capable in simulating, whereas BLAST, EnergyPlus, IDAICE
and IES <VE> are capable.
3. eQUEST has limitations in solar gain and daylighting calculations. It cannot create
optimized shading devices on its own or simulate reflection of direct beam solar
radiation from outside and inside window reveals (refer to Definitions). However, it can
work on user specified shading device scheduling and can simulate shading surface
transmittance. Simulation tools such as EnergyPlus, ECOTECT, IES<VE>, Tas and TRNSYS
are much more advanced and are capable of solar analysis and simulation with respect
to shading and daylighting.
4. eQUEST cannot simulate hybrid natural and mechanical ventilation or displacement
ventilation, whereas EnergyPlus, ESP-r, IDAICE and Tas are capable of simulating these.
81
5. At present eQUEST cannot simulate Solar Thermal Collectors, hydrogen systems and
wind power. TRNSYS is the only tool, currently, that can simulate these systems.
6. Low-temperature radiant hydronic and electric units are not simulated by eQUEST. This
was observed while simulating the modification of the building in question. Other tools
like EnergyPlus, BSim, BLAST, ESP-r and IES<VE> are capable to simulate this.
7. Some other challenges of eQUEST include Demand Controlled Ventilation and seasonal
heat and cold storage with Phase Change materials.
After discussing the above challenges of eQUEST, it will be interesting to state here that
Refrigeration Systems for Warehouse and Retail Food Storage and Ice Rink in building space are
a part of the capabilities of eQUEST and in fact, there are no significant other simulation tools
that can simulate these.
6.2 Conclusions made on the analysis of all simulations done in this research work
The results of all the simulations done in the present study have already been analysed in
Chapter 5. Based on the analyses, the following conclusions are drawn –
1. A reduction of 60 percent in the building energy use (not including the equipment
energy) has been achieved, as compared to the existing state of the building chosen as
the case for study. This building had been constructed 5 years ago and so may be
considered as a fairly recent construction. None of the changes that we have applied as
modification can be considered as extremely expensive or very challenging to use in real
time scenario. The simulation tool that we have used, i.e. eQUEST, has been globally
taken as being not a very sophisticated tool, with substantial limitations (refer Table
2.1). If a reduction of this huge magnitude (60 percent) is possible in this scenario, it is
undoubtedly possible to further reduce the energy use, by applying some more
sophisticated and expensive upgrades, like, natural ventilation, displacement
ventilation, automated blinds, adding a Ground Source Heat Pump among others.
2. The results of the simulations show that the biggest energy load in the building is due to
uncontrolled air leakage between the building and outdoor environment, also known as
82
exfiltration. This accounted for about 40 percent of the heat loss in the as- is-case. The
next largest heat loss occurs by conduction through building envelope. Thus, the two
most important recommendations for new construction would be –
I. The current practice in Canada for commercial building is between 0.1 to 0.6
ACH (refer subsection 3.3.3). It is critical to build a thermal envelope with 0.2 or
less ACH.
II. Instead of current R-11 thermal resistant of the as-is-case in question (refer
Table 4.4), to build a much more thermal-resistant building envelope, with up to
R-35 .
3. As the boiler and chiller used for heating and cooling are efficient electric equipments,
the main load being met by natural gas is hot water. All the remaining (largely reduced)
energy demands of the building are met by electricity. This demand can eventually be
met by green electricity or that produced by using wind, solar or geothermal energy.
Thus, the use of fossil fuels in buildings can almost entirely be eliminated and carbon
emissions greatly reduced.
6.3 Suggestions for future research based on this study
The most important suggestions based on this study that can be made for future research are
stated below:
1. A detailed cost benefit analysis can be carried out based on the recommended building
design, for the climate of Toronto. It will be crucial to find out, how much extra does it
really cost, if any, to build the envelope that we need and what is the payback time on
the extra cost. This suggested study, along with the current study, can play a vital role in
improving the current building codes and/or convincing builders to improve the
construction that they are doing currently.
2. A city level research study can be carried out based on the simulation results of the
modified new building designed in this study. Climate simulation tools can be used and a
detailed study of possible carbon reductions by applying the new construction can be
carried out. An estimate of possible reduction by renovating the existing buildings can
83
be incorporated as well. The effect of these improvements (in existing, as well as, new
construction) can be studied for the current scenario, as well as, future decades, in
order to get a clear picture of the possibilities of the extent to which the carbon
emissions can be reduced by improving efficiency and design in the building sector
alone.
84
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APPENDIX
Daily Schedules –
1. Building Occupancy Schedules
Weekdays–
87
Weekend –
88
2. Building Lighting
Weekdays –
89
Weekends –
90
3. Building Equipment
Weekdays –
91
Weekend –
92
4. Building Cooking Schedules
93
5. Building Fan Schedules
Weekdays –
94
Weekends –
95
6. Building Cooling Schedules
Weekdays –
96
Weekends –
97
7. Building Heating Schedules
Weekdays –
98
Weekends –
99
8. Winter Shading Schedule
100
9. Summer Shading Schedule