a comparative of innovative energy modelling...
TRANSCRIPT
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A COMPARATIVE OF INNOVATIVE ENERGY MODELLING
AGAINST CONVENTIONAL METHODS AND THE USE OF BIM TO
ASSIST IN IMPLEMENTING
By
David Austin
1102747
Architectural Design Technology
School of Technology
University of Wolverhampton
Supervising Officer: Dr David Heesom
Date January 2015
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UNIVERSITY OF WOLVERHAMPTON
ABSTRACT
A comparative of innovative energy modelling against conventional methods and
the use of BIM to assist in implementing
By David Austin
Supervising Officer: Dr: David Heesom
School of Technology
With strategies such as the 2025 construction strategy and 2016 building information
modelling target being recently developed, it has emphasised the focus on overcoming
inefficiencies in relation to energy usage both in the manufacturing and running of projects.
Inevitably this has led to scrutiny in achieving the optimisation of energy efficiency in a
design, this optimisation requires extensive design and analysis at the conceptual stage to
ensure the best solution is concluded avoiding unnecessary cost from post design
alterations.
This study investigates advancements of energy modelling against conventional methods to
present an overview of how the methodology that forms the basis of each study has evolved
to coincide with the advancements in technological resources available. Direct analysis is
used to compare the ‘traditional’ methods with the emerging approaches. The concluding
verdict of this analysis illustrates that within the construction industry the use of the new
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innovations offer a more practical and effective option. These options allow quick and
accurate analysis to be achieved in a less time and cost intensive method. These methods
over time will inevitably evolve as the technology available does to ensure even quicker and
cheaper solutions that will offer further in-depth extensive analysis.
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ACKNOWLEDGMENTS
The author wishes to express sincere appreciation to Dr David Heesom for his assistance in
the preparation of this manuscript.
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TABLE OF CONTENTS
Abstract .........................................................................................................................................i
Acknowledgements ................................................................................................................. iii
Table of contents ..................................................................................................................... iv
Table of figures......................................................................................................................... vi
Section 1: Introduction ........................................................................................................... 1
1.1: A general overview of the advancements of the BIM process ............. 1
1.2: Historical advancements of BIM and energy modelling ........................ 2
1.3: The future of energy modelling within BIM ............................................. 4
1.4: The importance of energy modelling within the initial ......................... 5
design stages
1.5: Aims & objectives ............................................................................................ 6
1.4: Organisation of the report ............................................................................. 7
Section 2: Wind tunnels vs computational fluid dynamics ............................................ 8
2.1: Introduction......................................................................................................... 8
2.2: Wind tunnel studies ........................................................................................... 9
2.3: Wind tunnel studies-the methodology ....................................................... 11
2.4: Computational fluid dynamics studies ....................................................... 13
2.5: Computational fluid dynamics-the methodology .................................... 13
2.6: A comparative analysis of wind tunnels & CFD’s .................................. 16
v
Section 3: Heliodon vs geo-located solar studies ........................................................... 18
3.1: Introduction .............................................................................................................. 18
3.2: Solar studies-the methodology ............................................................................ 19
3.3: Solar studies-the advantage of its use ................................................................ 21
3.4: Heliodon studies ...................................................................................................... 22
3.5: Geo-located solar studies ...................................................................................... 24
3.6: A comparative analysis of heliodon’s & geo-located solar studies ........... 27
Section 4: Conclusion ............................................................................................................ 29
4.1: The use of CFD’s for wind utilisation .............................................................. 29
4.2: The use of geo-located solar studies for solar utilisation ............................. 30
Bibliography ............................................................................................................................. 32
Appendix A. ............................................................................................................................. 36
vi
TABLE OF FIGURES
Figure Page
1: Glodon BIM overview ....................................................................................................... 1
2: BIM and the building lifecycle .......................................................................................... 2
3: The flow of air in an urban area ..................................................................................... 11
4: An example of a wind tunnel used for Chifley Square, Australia ......................... 13
5: An example of a vector plot representing a turbulent flow .................................. 16
around a sphere
6: An example of a x-y plot representing the temperature in .................................... 16
comparative to wind speed
7: An example of a solar path diagram representing the sun ...................................... 21
path over a 6 month period
8: An example of a typical heliodon ................................................................................. 24
9: An example of a geo-located solar study analysing solar ........................................ 27
radiation, shadowing and exposure
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S e c t i o n 1
INTRODUCTION- A GENERAL OVERVIEW OF HOW THE BIM
PROCESS COINCIDES WITH ENERGY MODELLING
A general overview of the advancements of the bim process
It is often conceived that BIM is simply specialised software that has frequently been used
predominantly in the Engineering discipline with only recent adoption by other members of
the Construction industry, e.g. Architects and Contractors (Heesom. 2014.) However as
shown in both Figure 1 & 2 it is much more than a software package that is used to design,
it is in fact a workflow process that relies entirely on full collaboration of all disciplines.
Figure 1: Glodon BIM overview (Glodon. n.d)
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This process covers all aspects of the design process to allow full production of all necessary
documents from conceptual design through to fabrication documents and finally an
Operation & Management database. As this flow progresses through the stages, relevant
documentation will be produced at each stage to reflect the revised RIBA plan of work
(2014).
Historical advancements of bim and energy modelling
As described by Bergin and Quirk (2012) the BIM process story is a ‘Rich and Complex’
one which consists of various key roles within it. As stated within the article the first
conceptual prospect of BIM was anticipated by Englebert (1962) where in his paper
‘Augmenting Human Intellect’ he described the future being a person designing on a screen
with elements that could be projected to a 3D model, both allowing for evaluations and
adjustments to suit. During the following 60 years there were vast advancements from the
Figure 2: BIM and the
building lifecycle
(Hegedus. 2012)
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initial concept that was presented by Englebert which have both lead to a structured work
flow as well as the creation of various software’s.
Whilst the BIM process was being developed there were also developments in Building
Energy Modelling. Building Energy Modelling can be traced back to 1925 with the
development of foundation algorithms such as Nessi and Nisolle’s Response Factor
Method which was the initial model for heat flow, however it was not until the 1960’s with
various documents produced by Mitalas and Stephenson that this method was used for
studies in heat transfers through walls which was the starting point of energy modelling
studies (Haberl & Cho. 2004).
In 1959 the American Society of Heating, Refrigerating and Air-Conditioning Engineers
(ASHRAE) was formed as a body in the United States that have pursued the optimisation
of mechanical services. During the 1960’s the body dedicated vast amounts of resources to
create computerised systems for both building management and calculations of air
conditioning, these later formed procedures for the calculations of heating and cooling.
Following the completion of these procedures there was the First International Building
Performance Simulation Conference that led to the development of substantial steps in
software development including the creation of packages such as TRNSYS (1975), Bentley
BIM (1997) and Revit (2010). These packages have enabled energy modelling to occur on a
computer interface as opposed to the standard ‘hands on’ approach previously used. This
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was further enhanced with the development of gbXML file formatting in 2000 to allow the
information to be transferred around the design group when needed, following the basic
principle of collaboration in BIM between disciplines as previously discussed (Haberl &
Cho. 2004). An in-depth timeline portraying the history of Building Energy Modelling can
be found in Appendix A.
The future of energy modelling within bim
BIM has already become a common practice within the construction industry with it being
extensively used prior to the Level 2 BIM requirement issued in the Government
Construction Strategy (BIS. 2011). Although energy modelling is widely used already it has
not been enforced as a requirement, therefore the majority of new builds do not do
extensive model analysis but instead use conventional design methods that save energy
instead of further exploring whether this can be improved.
As large international companies such as HOK, Arup and Kier start to adapt BIM fully and
with companies such as Autodesk supporting the energy analysis side of modelling, it
appears to a realistic expectation that in the near future companies will be using the energy
analysis tools on all projects ranging from a small residential build to a high rise office
building.
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The importance of energy modelling within the initial design stages
It is considered that by 2025 the construction market will grow by over 70 %, (DECC.
2013) with this substantial growth it will directly correlate with an increase in carbon
emissions, however it has been also been stated by the DECC that there is a target of 80%
reduction on carbon emissions by 2050 (DECC. 2013). In order to pursue this target it is
necessary for the construction industry to use innovative design methods that will both
reduce waste both during and post construction, as well as ensure high efficiency operation
of the building post to completion.
Energy modelling can be a key element to pursuing the emission target set by the
government as it is a process that can occur prior to formal decisions being made and can
present various options with their proposed outcomes in relation to energy usage, savings
and improvements. The use of methods such as wind and solar studies allow the design
team to analyse a concept over a set amount of time to see how it reacts to an accurate
portrayal of the environment it will be in and scrutinise where it can be improved before it
is taken to detailed design.
As stated in the Energy Efficiency Strategy ‘We estimate that through socially cost effective
investment in energy efficiency we could be saving 196TWH in 2020, equivalent to 22
power stations’ (DECC. 2012). Although the focal point for this initiative is the use of
innovative construction methods opposed to the initial design, it is essential to use energy
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modelling at the forefront of the design to optimise the building from the beginning of the
concept.
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Aims and objectives:
The aim and objectives for this report are outlined below:
Aim: The aim of this report is to explore emerging methods of energy modelling and their
effectiveness in comparison with conventional modelling methods whilst analysing a
building at concept stage.
Objectives: In order to meet the aims of the report the following items will need to be
analysed:
The importance of energy modelling methods and the theory behind the modelling
method
The ‘conventional’ methods of energy modelling analysis
The emerging methods that can be used as an alternative
A comparative study of the conventional method versus the emerging
Case studies analysing the effective implementation of the methods and their
alternatives
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Organisation of the report
The report will consist of a comprehensive study of the following energy modelling
methods:
Wind tunnels vs CFD’s
Heliodon vs geo-location solar studies
U value calculators vs energy analysis modelling
Within these chapters there will be a thorough analysis of the methodology that has defined
these studies as well as a comparative study on their effectiveness in relation to the area of
study.
The results of the comparative study will form the basis for the design of Bilston Primary
School using the effective methodology discovered to influence the design in respect to
wind flow through the site, the orientation for solar influence and effective design for
energy efficiency.
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S e c t i o n 2
WIND TUNNELS VS COMPUTATIONAL FLUID DYNAMICS
Introduction:
It was discovered in a study undertaken that out of a measure of 356 public buildings 50%
of these possessed improper ventilation which had a direct effect on the welfare of the
users. This was referred to as ‘Sick Building Syndrome (Wallingford, Carpenter. 1986).
Following this study it has become an important aspect to be considered in the design stage
with the implementation of Building Regulation Approved Document F to reinforce the
need for adequate ventilation with appropriate guidance in how to achieve this.
In addition to this document there are further readings in relation to sustainability that
discuss various aspects including ventilation, these further readings include various BRE
guides. As stated within the Design Quality Buildings: A BRE guide (BRE. 2006) designers
should consider the following aspects during the design process:
Occupants and passer-by are not subject to wind funneling effects
The structure of the building should be designed to withstand wind pressure, water
penetration and wind loading
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The orientation of a building directly effects ventilation and natural light. Careful
consideration of this is key to comfort, avoiding deterioration and cost saving
Local effecting influences such as altitude, ground level, topography, speed and
direction of wind, season, location and terrain
These considerations if explored correctly inform the design process to create an effective
solution that will promote ventilation in and around the site.
During this design process the use of analytic methods for wind flows has been commonly
explored, especially in projects with high rise buildings and turbulent wind conditions. The
use of these methods have allowed the simulation of various wind conditions to be applied
to a mass to portray how elements such as vortex’s (a spinning formation of air) and wake’s
(an area of no movement behind an obstruction) would be effected by both varying
conditions and making alterations to the mass itself. In addition to this the systems used for
analysis allow for adjustments to be created to accurately mimic the site conditions correctly.
Wind tunnel studies
Wind tunnel studies have been predominantly used throughout the engineering discipline
with particular usage in automotive and aircraft design analysis. However between the
1940’s and 1950’s the use of this technology was first used in analysing the effects of wind
flow on a building using the typical wind profiling found in the atmosphere, uniform and
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velocity profiles (Blackmore. 1997). Although this method had been used frequently in
other disciplines it was discovered in the 1960’s that the tunnels did not possess an accurate
portrayal of the atmospheric layer. This layer in the real world circulates 1km above the
surface and circulates around the circumference. As a building is erected it will penetrate the
layer and create a 3D flow to which fluctuates the results previously, the effect of this
penetration on the layer is shown in Figure 3 below. In order to recreate this, devices were
created to obstruct the flow and create the necessary accurate atmosphere (Lawson. 2001).
Figure 3: The flow of air in an urban area (Cengiz. 2013)
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Lawson describes one of the functionalities of a wind tunnel investigation as a means of
testing pressures on a building (Lawson. 2001). However, wind tunnels offer much more
information including the data and visuals that are produced testing turbulences, velocities
(mean and fluctuating) and flows (Scanlan. 1978). These vital pieces of information can help
a designer understand the reasoning behind the results. As mentioned, one of the elements
that is measured during the investigation is the assessment of wind speeds at a pedestrian
level using either an Irwin Probe (a tube that measures the pressure differences from the
base to the top to calculate velocity) or Hot Wire Anemometer (2 thin pieces of wire that
run electric current through to measure the cooling that occurs when a flow passes
through). This study then allows measures to be implemented in the massing of the model
to tackle any issues of turbulent flow that may occur.
Wind tunnel studies- The methodology
The basic principle behind a wind tunnel is the use of large scale industrialised fans within a
tunnel environment to simulate the flow of wind that would be experienced in real world
situations. However due to the wind fluctuating in profile the use of flaps, shutters, grids
and fences are used to mimic the different profiles that may occur with adjustments being
controlled via specialised computer software (Scanlan. 1978), an example of a typical tunnel
can be seen in Figure 4. These simulations can then be transposed into either data or visuals
depending on the desired outcome required, for instance a smoke photo may be used to
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show the flow of the wind where as a x-y plot may be used to show the fluctuation of
velocity (Tu, et. al. 2012).
Figure 4: An example of a wind tunnel used for Chifley Square, Australia (National
Instruments. N.D)
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Although the use of wind tunnels has been perceived as an accurate solution to modelling,
with examples of uses including the development of aerodynamics for fighter jets, this is
often a perception that is not entirely correct. Due to the restriction in sizing for the tunnels
it is difficult to mimic the requirements for aspects such as the correct flow in relation to the
Coriolis Effect (the rotation of wind flow to compensate for the earth’s rotation and heat
flow) (Scanlan. 1978) and the creation of a correctly scaled velocity in respect to the scale
model used (Lawson. 2001). In addition to this the data produced for these simulations can
only run for a short duration not allowing full month or year analysis.
Computational fluid dynamic studies
Computational fluid dynamics (CFD) is a methodology that has been used throughout the
aerospace, automotive, biomedical, civil and environmental engineering disciplines. The
basic principle behind this simulation is the translation of mathematic fundamentals used in
wind tunnels to create virtual profiles that can be represented as flows in computer
simulation (Tu, et. al. 2012). These simulations are run for a time lapsed amount of time to
determine factors such as air velocity, flow rate, air pollution and thermal balancing within a
building (Athenitis, Santamouris. 1986).
Computational fluid dynamics- The methodology
Unlike the wind tunnels, the steps of creating a CFD revolve solely around the use of
computer software to create the geometry and meshing of the building before specifying the
appropriate physics and boundary layer to run simulations with. As mentioned previously
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the use of a CFD method can allow for multiple testing to be simultaneously ran for various
scenarios, something a wind tunnel cannot do without multiple tests (Tu, et. al. 2012). In
addition to the creation of a simulation much like the wind tunnels there is also the
additional features that a CFD offers including the creation of a Dynamic Simulation Model
(DSM) to create time lapsed visualisations of the simulation for review including:
Vector Plots (Velocity presented in arrows for flow direction with size relative to
magnitude)
X-Y Plots (A chart representing various comparatives such as fluctuation in velocity,
temperature in comparison to wind speed as well as various others)
Flooded Contour (Much like a thermal image it portrays data in colour for severity)
Streamline Plots (A representation to show the wake recirculation zones)
Data Reports
Further to this there is also analysis that can be undertaken in a model on additional aspects
such as internal ventilation, temperature and CO2, something wind tunnels are unable to
produce (Jankovic. 2012).
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Although there have been issues with CFD’s producing errors that may have looked correct
in the visuals but the data has not quantified correctly (Tu, et. al. 2012), the advantages have
by far outweighed the initial issues as the approach is adopted by construction. As described
in Computational Fluid Dynamics (Tu, et. al. 2012) the advantages include:
The ability to study specific terms within a fundamental equation to conclude why a
result has acted how it has
Simulate real fluid flows using a low cost and low time consuming method
Figure 5: An example of a vector plot
representing a turbulent flow around a
sphere (TVT. 2011)
Figure 6: An example of an x-y plot
presenting the temperature in
comparative to wind speed (UCLA. 2007)
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Simulate various scenarios using the same model simultaneously
Creation of visualisations that are able to be reviewed by the team and presented
externally
Evaluation a range of parameters
Allow temperature to be shown in addition to the flow of the air
A comparative analysis of wind tunnels & CFD’s
Overall the essential methodology behind wind tunnels and CFD’s are the same with only
variations on the creation method of the model and the presentation of the results. With
this being said, CFD’s have followed the common trend of utilising an ever evolving
computer age which saw hand drawings develop to 2D and now 3D integrated design
methods. With this age it has allowed a time and cost consuming method of wind tunnels
be transformed into a simplified computer interface that summaries the decades of
development for the wind tunnel to allow a model to be created, tested, analysed and
adjusted in a much less cost and time consuming exercise.
In addition to this as the use of CFDs is still developing as they are adapted further by the
construction industry, and with computers becoming more capable of dealing with large
algorithms, the use of this method has great promise in becoming a more efficient and
predominant use for air flow studies as it offers more functionality in relation to various
studies that a wind tunnel cannot offer. However, much like the automotive industry the use
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of wind tunnels will still be coincide with the computerised alternative as they both
complement each other and ensure a convergence in data.
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S e c t i o n 3
HELIODOM VS GEO-LOCATED SOLAR STUDIES
Introduction:
The use of the sun as a guiding element for building position and orientation has been dated
back as far as the Classical Greek period (500-336 B.C) with observations being
documented by Socrates. During his time as a philosopher he noted that in the summer
seasons houses with a southern orientation would allow sun rays to penetrate the porches
whilst in the winter the sun would pass overhead and create a shaded area (Perlin. 2013).
These observations have developed over the following 2,500 years to create the principles
behind Passive Solar Design:
Orientation
Shading
Passive solar heating & cooling
Sealing the building
Insulation
Thermal mass
Glazing
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Skylights
(Australian Government. 2013)
Each of these principles is an aspect that needs to be taken into consideration at the
concept stage of design to optimise the buildings utilisation of the sun throughout the year,
as stated within Introduction to Architectural Science: The Basics of Sustainable Design ‘To
effectively design the designers need to understand the movement of the sun and the energy
flow and has to handle it’ (Szokolay. 2003).
In order to assess whether the design has used the principles effectively, the use of solar
studies is required to measure the scheme and assess it in regards of areas that could be
improved. The use of solar studies has been extensively used throughout architectural
design for many years with it now becoming more predominantly used as sustainable design
has become a key aim within projects.
Solar studies-The methodology:
As previously mentioned the use of the sun’s rays as a method of natural lighting, heating
and shading has been commonly used since the Classical Greek period. As shown in Figure
7 the sun follows an orbiting path that varies according to the seasons, these variations see
the summer period sun path to be 23.45 degrees higher than the central line and 23.45
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degrees lower than the central line in the winter period. This is a presented as a two labelled
curved lines in Figure 7. As shown, the winter line is a less curved line which translates to
less day light hours at a lower angle; whereas the summer line is more curved at a higher
angle presenting more solar rays exposure. These sun paths are presented in solar path
diagrams that are unique to each site as they coordinate the site longitude and latitude with
the date and timing.
Figure 7: An example of a solar path diagram representing the sun path over a 6
month period (System Site Buildings. 2010)
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The solar path diagrams are then analysed to create the site environment, either manually or
digitally, before a model is tested, analysed, altered and tested again until the solution
resembles the objective sought for originally.
Solar studies-The advantages of its uses:
It has been observed that designers often rely on “rules of thumb” and their own
experience to make decisions on designs, however this can be misinformed and result in
errors (Lam.1999 cited Osser. 2007). Therefore the use of solar studies at the forefront of
the concept design is vital to ensure problems are discovered at an early stage to avoid issues
that can cost time and money, the use of these studies could potentially present where there
could be issues of glare to the users, inadequate lighting and shadowing.
An effectively designed building can both exploit the solar gains presented on the site whilst
ensuring the comfort of the users is maintained. As Hawke (1996) described, an effectively
orientated building ‘can receive sufficient amount of passive solar gain to offset the heat it
will lose’. In addition to the reduced need for heating due to the solar offset, the effective
design can also reduce the need for electric lighting which will in turn reduce the amount of
heat produced by these elements (Demetriou. n.d).
As mentioned previously the exploitation of these gains can also ensure the comfort of the
users, studies have shown that:
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Good use of daylight and sustainable design can raise rate of production by 1%
Increase productivity, improve health, lower absentee rate, create better grades
Improve the moods of the users
(Krygiel, Nies. 2008)
Heliodon studies:
As mentioned earlier, the sun follows a certain path dependent on the date, time and
location, the use of a Heliodon can mimic this precisely to create a simulation of how the
sun will react to on the building and its surroundings. A Heliodon can vary in its
appearance; however the basic principles behind them are always the same. As shown in
Figure 8 it consists of a table that houses the scaled model; this is orientated correctly to
ensure the buildings true north corresponds with the tables true north, attached to the table
are 6 rows of lights (each row corresponding to a period of the year) which each have 12
lights representing the hours of the day that are light. As the light varies site to site the lights
are adjustable to account for the location of the site on the hemisphere.
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The Heliodon has progressed over time with
the first models using a simple light that
allowed the table to revolve around it,
however over time this has seen the
development to a stationary table that has
revolving light units to mimic the seasons
and time. This has further progressed with
institutes such as MIT and EPFL creating advanced systems. MIT has developed an
automated tabled system that works using a control interface to mimic lighting conditions
of a location, time and date with camera facilities to document the findings (Osser. 2007).
EPFL have kept to the typical Heliodon with a static model, however they have created a
116th scale artificial sky ratification to mimic the sky conditions. Due to this environment
being so large it is capable to house larger models which can house sensors that can be
monitored and evaluated (Szokolay. 2003).
The use of a Heliodon as a tool in the solar studies on a building present various advantages
including:
They allow the user to move around the model in real time to see how it affects areas
Figure 8: An example of a typical
heliodon (HPD. 2008)
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A crude model can be analysed for summer, winter and spring/fall far more
efficiently and affordability than its digital equivalent
The analog tools are generally more intuitive and transparent allowing people to use
them easier and comprehend the data
(Canadian Architect. n.d)
Although there are these advantages for the use of a Heliodon there are also disadvantages
that need to be considered:
Fragility needs to be considered for physical models as delicate pieces get attached
and removed and breakages can occur (Osser. 2007)
The Heliodon cannot replicate cloud cover which can affect effectiveness drastically
(Szokolay. 2003).
Over simplification based on mean temperatures used can conceal true detail
(Szokolay. 2003).
A compromise of size of the building to be tested as the building requires to be scaled
down to fit the facilities, this does not properly portray the intensity of light or heat
and does not fully show areas of concern (Cheung, Chung. 2001)
Geo-located solar studies:
Much like CFD’s geo-located solar studies revolve solely around the use of specialised
software’s, the use of these software’s can either replace or aid the typical manual Helidon’s
26
that have been used previously. These software’s include developments by various leading
producers including Bentley and Autodesk, unlike the Heliodon’s the use of the software
offer more extensive options of what can be analysed including:
Solar studies- Daylight and shadow effects over a short and long duration presented
as an animation
Solar radiation analysis- Study of solar radiation on selected surfaces
Conceptual Energy Analysis- Create an energy model for analysis of thermal zones
and adjustments based on results
Thermal analysis- Heat loss and gain, loading and comfort levels
Creation of vertical sky component’s to calculate adequate lux levels through
windowed areas
(Horvat, Wall. 2012)
The principle behind a digital solar study remains the same as the Heliodon; however the
technique behind the study is more advanced than the manual alternative and therefore
offers more in-depth and accurate analysis. Much like the Heliodon, a model needs to be
created that will be situated within a site area with the appropriate massing surrounding the
site, this remains the same with the digital alternative however as the interface has an infinite
drawing plane it is able to create a scale model of the site and building creating more
detailed and accurate results.
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Upon completion of the model, much like the Heliodon, the conditions of the site are
created to mimic the daylight over a period of time. Unlike the Heliodon the software uses
Geostationary Satellite data to produce the weather simulations used, these data files can
account for issues such as aerosols, ozone deterioration, Rayleigh scattering and cloud
effects (Min-Yeom, Soo-Han. 2009). This sophisticated data allows future predictions to be
made over average assumptions which allow life time analysis to be achieved in a relatively
short period of time and effort (Jankovic. 2012).
Figure 9: An example of a geo-located solar study analysing solar radiation, shadowing
and exposure (SHC. 2012)
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The use of Geo-located solar studies has been proven to be advantageous in the
development of a scheme with examples such as The Greenland National Institute. This
institution used a ‘rule of thumb’ approach when designing the scheme with large windows
being south facing to utilise the sunlight and theoretically the heat gain. Although, due to the
site being located in a cold climate the heat generated from solar gain did not equate to the
loss from using a poor insulating material such as glass (Szokolay. 2003). Issues such as
these would not have been picked up on a Heliodon simulation as this type of test would
solely focus on the light exhibited on the building yet if a computerised alternative was
produced it would have shown the issue prior to construction.
Although the use of the digital simulation offers many advantages over the manual former
method there are disadvantageous that need to be considered. The first main issue is the
time consumption that needs to be given into producing the model as each element needs
to be created individually in order for an accurate analysis on issues such as temperature
transference. This time consumption is completely dependent on the competence of the
user and the complexity of the scheme. Another issue that has become more relevant in
recent past is the inability of software’s to deal with complex surfaces, particularly curved
and shiny surfaces. These have seen issues such as glare not being correctly identified in
activity areas (Osser. 2007).
A comparative analysis of heliodon’s & geo-located solar studies
29
Although the use of a digital alternative is often perceived as a better solution for means of
simulations, the use of both methods presents both advantages and disadvantages. The use
of a physical model can be perceived as an easier method as it is a group of simple forms
orientated correctly with a preset apparatus presenting a visualisation. This being said the
results from this are limited to a simple visualisation whilst a digital counterpart could
present more in-depth analysis in respect to light, shade, energy analysis etc but take more
time to produce.
A study was undertaken by Osser that used both the method of a Heliodon as well as
Autodesk’s Ecotect on the same scheme. This study showed that the size and scale of the
model as a physical piece did not allow for a full thorough investigation, yet the use of
Ecotect allowed a comprehensive study with presentable data. Although this would seem to
show the digital alternative as the better option it was stated that due to the complexity of
the software it would require an experienced user or result in errors being made that would
affect all data produced (Osser. 2007).
In order to successfully test and present a project it will require both methods to be
undertaken, as stated by Osser and Raselin (2007) the use of a digital model and visuals are
hard to present to the cliental as they require explanation to interpret, whereas the Heliodon
allow the clients to walk around them and see firsthand the impact on the structure. The
ideal solution therefore would be to use a scale model for client presentation whilst creating
digital models for testing and calculating.
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S e c t i o n 4
CONCLUSION
Following the study into the various aspects of design that should be analysed and the
effectiveness of the methods for analysis it has proven how essential the incorporation of
these test at the forefront of the design and how they can ensure errors are reduced that will
effectively save time and money.
The Use of CFD’s for wind utilisation:
The study of wind behaviour on an object is often perceived as something that is purely
focused at the design of automotive and aerodynamic projects, but without careful
consideration of this aspect on a building it could result in a number of issues such as
insufficient ventilation, excessive wind flow at pedestrian level or suction around edges
causing velocity.
In order to effectively implement good practice in relation to wind loading of the building
the scheme will be formed to optimise streamlining from a prevalent face and channel this
flow towards the natural ventilation channels that will be incorporated in the scheme. In
31
addition to this careful consideration will be taken to ensure there will be structures created
to ensure a wake for pedestrians as they flow around circulation paths.
To ensure the design optimises the utilisation of wind in a favourable manner the site will be
replicated using CFD software at an early stage and geo-located to ensure accurate portrayal
of the wind conditions upon completing of this. Options will be devised to evaluate the best
concept for creating natural ventilation and comfortable movement are the building. The
use of this software opposed to the wind tunnel alternative will allow more options to be
tested in a quicker and cheaper way.
The use of geo-located solar studies for solar utilisation:
Although the study of solar behaviour and utilisation on a site are often evaluated in
projects it is often not effectively implemented as designers base their ideas on ‘rule of
thumb’ theories. In previous schemes it has been known for a design to focus on utilising
the south orientation without consideration of heat loss creating walls that lose more heat
than create.
During the design of the concept aspects like these will be considered to ensure they are
avoided, instead the building will consist of an a array of various windows, both high and
low level, that will utilise the gains created on the fascia whilst maintaining a comfort level
within the structure. These windows will be coordinated with the ventilation stacks to
32
ensure that during both the winter and summer a comfort level is maintained that does not
require extensive mechanical assistance.
The use of a digital simulation to evaluate the effect of the sun on various designs will allow
a year round simulation to be achieved in a more realistic timeframe. In addition to this,
unlike the use of a Heliodon different conditions can be replicated that could occur such as
overcasting. By using this method the location of the windows can be defined based on how
the model reacts.
33
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APPENDIX A
33
A History of Building Energy Modelling (Haberl, J. Cho, S. 2004)