ar50354 kayina japfiio ies submission

7/31/2019 AR50354 Kayina Japfiio IES Submission

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AR50354 BUILDING ENERGY MODELLING

IES COURSEWORK SUBMISSION

JAPFIIO KAYINA

2011-12


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1. INTRODUCTION

The building to be modelled is of an English and Drama building proposed to be built in Bath whichcomprises of three classrooms and a large performance space. The building is modelled completelyin IES Virtual Environment and various performance parameters will be tested by running

simulations with different settings. The Building bulletin 101 and Energy performance guide will bereferred to extensively throughout the report. The present simulation does not take into accountthermal bridging.

2. MODEL SET-UP

a) Views from two directions

Figure 2a-1 shows the investigated building from the north-east showing the entrance to thebuilding and the large glazed areas of the hall space. Figure 2a-2 shows a view from the south-westshowing the classrooms. Clerestory windows are also clearly visible in both the views.

b) Daily weekday occupancy and lighting profiles for classroom and hall

Figure 2b-1 Daily weekday occupancy profile for classroom

Figure 2a-1 View from north east Figure 2a-2 View from south-west


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Figure 2b-3 Daily weekday lighting profile for classroom

Figure 2b-4 Daily weekday lighting profile for theatre

Figure 2b-3 Daily weekday classroom lighting profileFigure 2b-2 Daily weekday occupancy profile for theatre


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c) Construction details used for walls, roof, floor and windows

Figure 2c-1 Summary of different types of constructions used in the building

Figure 2c-2 External wall construction details


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Figure 2c-3 Internal wall partition details

Figure 2c-4 Roof construction details


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Figure 2c-5 Floor construction details

Figure 2c-6 Window construction details


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Figure 2c-7 Additional derived parameters for glazing

d) Room conditions, system, internal gains and air change settings for Classroom A

Figure 2d-1 Room conditions in Classroom A Figure 2d-2 System settings in Classroom A


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Figure 2d-3 Internal gains Lighting Classroom A Figure 2d-4 Internal gains People in Classroom A

Figure 2d-5 Internal gains Computers in Classroom A Figure 2d-6 Internal gains Whiteboard projector in Classroom A


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Figure 1 Air exchange settings for Classroom A

e) Room Data and Internal gains settings for theatre

Figure 2e-1 Room data for theatre Figure 2e-2 Internal gains - Lighting in Theatre


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Figure 2e-3 Internal gains - People in theatre

f) Apache systems window showing building services used

New Heating system

Figure 2f-1 Apache system settings for room heating Figure 2f-2 Cooling set as natural ventilation


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Hot water system

Figure 2f-3 Heating system - Auxiliary energy settings

Figure 2f-4 UK NCM settings - Heating system

Figure 2f-5 UK NCM settings - Ventilation

Figure 2f-6 Hot water system settings Figure 2f-7 Auxiliary energy settings


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g) Simulation setting window showing the options used for simulations

The screen grab shows the use of weather file for Bristol and simulation timestep set to2minutes,reporting every 10 minutes from 1 st January to 31 st December.

h) If the thermal bridging for the project has a Y-value of 0.10w/m 2K, the sum of this value and thepresent project U-value of a particular construction will give the target U-value of that construction.This may be repeated for any externally exposed construction to obtain the target U-value. To modelthis target U-value in IES, some realistic U-values may be entered for the different layers in aconstruction to ultimately reduce the U-value to target value.

3. ENERGY PERFORMANCE

a) Monthly breakdown of total energy consumption and CO 2 emitted by the boiler, lighting,equipment and total for whole building.

Table 3a-1 Monthly breakdown of energy consumption by sectors in MWh

Figure 2g-1 Simulation settings used


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b) Heating load as a function of internal air temperature and external temperature for first weekin January in Classroom A

c) Simulation 2

The thermal resistance of a material is a function of the thickness and the conductivity of thematerial. Considering the insulation layer to be homogeneous and its conductivity to be constant, anincrease in the thickness of the insulation layer will increase the overall thermal resistance of theconstruction. Therefore, the thickness of the insulation layer is increased to achieve double thethermal resistance of the walls and roof as compared to the base case simulation. This simulationwas named as Simulation 2.

Table 3a-2 Monthly breakdown of carbon dioxide emissions by sector in kgCO 2

Figure 3b Graph showing heating load as a function of internal temperature and externaltemperature


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d) Comparison of room heating load for the base case simulation and simulation 2

Figure 3d Room heating loads for the base case simulation and simulation 2 for classroom B in the first week of February

4. VENTILATION AND INTERNAL AIR QUALITY

a) Formula used to control the window opening on the daily profile

Figure 4a IES Screenshot showing formula for window opening


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b) CO2 concentration for Classroom A in April

In April, the CO 2 concentration in Classroom A reaches a maximum of 1474 ppm while maintaining amean value of 634ppm.

c) Volume of air exchange through windows on the south facade of Classroom A for the first fullweek in April

Figure 2 Graph showing volume of airflow through windows in l/s

Figure 4b Graph showing the CO2 concentration in classroom A in base case simulation


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d) Volume of air exchange through the clerestory windows in Classroom A for first weekm of April

Figure 4d Volume of air exchange through the clerestory windows

e)Comparison of CO 2 concentration for classroom A in Base case simulation against simulationwith clerestory windows closed for the first week of April

Figure 4e Comparison of CO2 concentration with clerestory windows open and closed

Table 4e-1 CO2 concentration when clerestory windows are open

Table 4e-2 CO 2 concentration when clerestory windows are closed

1500 ppm BB101 standards


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According to the recommended performance standards mentioned in Building bulletin 101, theaverage CO 2 concentration should not exceed 1500ppm for any occupied time of the day. FromTable 4e-2, it is evident that the peak CO 2 concentration in Classroom A does not exceed the limitsalthough it is evident from the Figure 4e that the slightly increases when the clerestory windows areclosed. The difference in the peak CO 2 level was marginal at about 62ppm while the mean CO 2 concetration is well under performance limits in both cases. This implies that the openableclerestory windows may be value engineered out to decrease sohphistication in buildingmanagement systems and cost implications. The clerestory windows may however be used as fixedwindow lights for daylighting purposes.

5. SUMMERTIME OVERHEATING

The Building Bulletin 101 prescribes 3 conditions out of which a minimum of two should be met forcompliance with Approved document L2 for teaching and learning areas inorder to avoidoverheating during 1 st May and 30 th September. The conditions are:

a) There should be no more than 120 hours when the air temperature in the classroom rises above28C

b) The average internal to external temperature difference should not exceed 5C (i.e. the internalair temperature should be no more than 5C above the external air temperature on average)

c) The internal air temperature when the space is occupied should not exceed 32C.

Base case simulation results for investigated building

Investigation 1:

Figure 5a-1 Number of hours when internal air temperature exceeds 28C


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Investigation 2:

Table 5a-1 Difference in internal and external air temperature

Table 5a-1 shows the different temperatures at different times of the day on 1 st May at varyingexternal temperatures. It can be deduced that the internal temperature exceeds the externaltemperature by more than 5C in most period of the day. This pattern continues for other months of . the period that is mentioned in the Building bulletin.

Investigation 3:

Figure 5a-2 Number of hours when temperature exceeds 32C


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Space Condition 1 Condition 2 Condition 3 Approved L compliant

Classroom A

Classroom B

Classroom CTheatre

Table 5a-2 Demonstration of compliance to requirements by Building Bulletin 101

b) Maximum temperatures in classrooms and theatre.

Table 5b-1 Maximum temperatures of classrooms and theatre occurring within the time period considered by BB101

c) Proposal to reduce internal temperatures (Simulation 4)

Figure 5c-1 View of south facade with external shading on classroomwindows

The application of external horizontal shading device above theclassroom windows can bring down the internal temperatures toacceptable levels.

In this particular simulation 4, the designed shading devicesproject from the wall surface by 1m and are of a thickness of

Figure 5c-2 Close up view of externalshading


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Investigation 3 Maximum and mean temperatures

Figure 5d-3 Reduction in maximum and mean temperatures

Improvements and compliance to BB101 standards

Space Condition 1 Condition 2 Condition 3 Approved L compliant

Classroom AClassroom B

Classroom C

Theatre

Figure 5d-4 Demonstration of compliance to BB101 standards after alteration to design

6. POTENTIAL GLARE AND SHADING

The following sets of images show the pattern of direct sunlight penetrating into the

interiors of a typical classroom at morning, midday and afternoon throughout the differentmonths of the year. One single day, i.e. 15 th of each month has been considered for this.

Month Morning 9:00 Mid-day 12:00 Afternoon 15:00

January

February


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March

April

May

June

July


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August

September

October

November

December


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b) Potential times and locations for glare

For this simulation, a local shade was drawn in each of the classrooms at a height of 0.80mto represent the working plane of the student desks. The lighter tint of yellow in the imagesrepresent the sunlight falling on the working plane. More area of the yellow signifies moresurface area which has direct sunlight incident on it.

The potential for glare on the students desks is, maximum during the winter months whenthe sun angle is low. This is caused by the deeper penetration of direct sunlight into therooms. It is evident that, in January, February, November and December, sunlightpenetrates up to a 50% depth of the room from 9am to 3am. This is admitted through thewindows on the south faade. The level of sunlight penetration significantly reduces oncethe summer months approach. The potential for glare is minimum during the months of June and July when the sun angle is high.

Throughout the working hours, there is high potential for glare for students seated near thewindows throughout the year. This problem gets worse during the winter months asmentioned earlier. On the other hand, there is reasonably lower risk for glare for studentsseated away from the windows.

c) Design recommendations to mitigate glare

In Figure 5c-2, the application of vertical shading devices slightly mitigates the risk for glareon the working plane. This is evident in the set of images below in the slimming of the

beams of light entering the room. The following images are simulated for 15 th January,taken as an example in this case, as the risks are highest in the winter months.

9:00 12:00 15:00

Although this design recommendation may work in other cases, locations or design features,it is not very successful in this case because of the sun angle being very low. In this type of situation, it may be preferable to consider the use of controllable internal shading devicessuch as venetian blinds.

January


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The investigated building covers a total area of 456m 2. The electricity consumption persquare meter of floor area is 59.552 kWh/m 2. Thus, the electricity consumption of thebuilding is over two times higher than the energy consumption benchmark for a secondaryschool (refer Figure 7a-1). The natural gas consumption is 77.495 kWh/m 2. In this case, the

energy consumption is almost half of the benchmark standards.Although the hot water heating demands may be normal, the high energy electricityconsumption may be because of the lighting fixtures that are on throughout the occupiedperiods regardless of illumination from natural day lighting. Additionally, the computers,whiteboard projectors and other accessories which are on throughout the day add up to thehigh electricity consumption. This may be reduced by developing a new pattern of energyusage which uses energy only when it is absolutely required especially in the case of electrical equipment and lighting fixtures. The possibility of natural day lighting should alsobe realised and exploited.

Internal air quality and ventilation regimes

The following study on performance of the building in terms of air quality and ventilation isbased on the standards given in Building bulletin 101.

The minimum requirement of supply of external air ventilation rate of 3 l/s per person ismet in all cases in all the spaces. The daily average requirement of 5 l/s per person is alsomet throughout the year in all the spaces. However, the capability to achieve 8 l/s perperson at any occupied time is not achieved in many situations. This is particularly worseduring the summer months and in the theatre. The capacity of 8l/s per person however, is a

recommendation and not a necessity. Therefore, it is safe to say that the building isacceptable in terms of the ventilation rate provided.

3l/s per person

5l/s per person

8l/s per person


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The building bulletin 101 also mandates keeping the CO 2 concentration in all occupiedspaces to be below 1500ppm at any occupied time. This is achieved in all the classroomsand the average CO 2 concentration is kept low at most times making it acceptable. On theother hand, the theatre shows high maximum concentration of CO 2 at some selected

periods of the year which is unacceptable. This may be amended by providing higherventilation rates in the theatre with the use of fans to assist the flow of air. The number of fans to be used and placement will be critical to find a balance with energy consumption.

Summertime Overheating

As discussed in section 5 of the report, the building passes the first condition of maintainingless than 120 hours where air temperature was more than 28 C. However, it fails on theremaining two conditions. Thus, according to Building bulletin 101, the building at the basecase simulation stage is not acceptable in terms of summertime overheating. The use of external shading devices improved the performance in subsequent simulations.

Direct solar penetration using Suncast

The Suncast studies showed high levels of direct solar penetration in the classrooms during

winter months. This presented high risks of glare discomfort at the working plane. Thiscould be amended to a small extent by the use of vertical shading. However, other optionssuch as the use of internal shading devices such as blinds are recommended.

b) Recommendations for improvement on energy performance

For overall improvement on energy performance of the building, a few of therecommendations that can be pointed out are :

Exploration in effective usage of thermal mass can effectively reduce both heating

and cooling loads. An increase in suitable thermal mass would reduce the U-value of the constructions and thereby reduce energy consumption.

The building is currently oriented in the E-W direction on the longer side. This facesthe south faade of the building to face the sunlight directly incident on it. A slightshift in orientation can reduce overall energy consumption by reducing cooling loads.

The current usage pattern of electricity especially regarding lighting and equipmentis wasteful in the sense that it is on throughout the day with disregard to daylightingand illumination levels. A change in the usage pattern for use only when it isabsolutely necessary can but energy use.


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The glazing ratio in the north faade of the theatre is very high and is observed in theway that the theatre is overheating in many cases as mentioned in previous sections.Therefore, a lower glazing ratio should be devised to reduce overheating and coolingloads.

REFERENCES

(1997). Energy Consumption Guide 73 : Saving energy in schools. Watford: BRECSU.

(2006). Building Bulletin 101:Ventilation of school buildings.

Carbon Trust. (2007). Schools : Learning to improve energy efficiency . Retrieved April 1, 2012, fromhttp://www.kingston.gov.uk/learning_to_improve_efficiency_in_schools

CIBSE Guide B :Ventilation, Air conditioning and acoustics. (n.d.). Watford: BRE.

NBS. (2010). Approved Document Part F, Ventilation: Means of Ventilation. NBS.

ar50354 kayina japfiio ies submission

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