Contents
1. Building Description
02
2. Base Case
08
3. Improvement Strategies
12
a. Nottingham
12
b. Singapore
16
4. Update Energy Simulation
20
5. Similarities and Differences
24
6. Further Recommendations
26
7. List of figures
27
Building Description
Office building typology has become a major architectural feature determining the economic identity of a place. For the comfort of its inhabitants it employs active mechanisms of regulating building environment. With rising concerns of energy depletion and carbon footprint, it is essential to control and minimize usage of energy. The client having introduced the design, it is essential that a proper energy model and analysis can be prepared to visualize the key areas of energy consumption, as well as take measures to reduce it. The building is an integration of educational and office typology, with classrooms distributed on ground and first floors, while offices are on first and second floors. For the base run, the building’s longitudinal axis is assumed to be aligned along the no-
Figure 1: External wall detail, base design
rth-south axis, thus the office façade faces west, and the corridor is due east. The services and BOH areas are mostly clubbed together and in the southern part of the building, where a staircase connects all the floors. The base model has two types of wall, internal and external, which differs in terms of plaster and thickness. For maximum daylight both the east and west façade is assumed to have continuous glazing for the base run. Thus, the mullions are of timber, with 6mm single glass in the panel. Two types of mullions are used here, H-shaped and rectangular ones. The floor and roof slabs are of concrete while the false ceiling is of gypsum boards above which is the HVAC ductwork. The construction details of the elements are presented in figures 1 to 8.
Figure 2: Internal wall detail, base design
Figure 3: Glazing detail, base design
Figure 4: Mullion detail, on curtain frame
Figure 5: Floor slab detail
Figure 6: Roof slab detail
Figure 7: False ceiling detail
An important consideration is occupant density, which has been assumed to be of 10m²/person for classrooms, offices and other public areas, while the Revit default value of 33m²/person is taken for services/storage/BOH areas. The gross slab area at each level is 1290m²
Table 1: Space schedule - 2nd floor Table 2: Space schedule - Ground and 1st floor
To calculate the internal heat gain, three parts are essential; load from people, lighting load and power consumption by other devices, since all the energy is finally converted into heat. Sensible Heat Gain from people is set at 73.27Wpp and Latent Heat Gain is 58.61Wpp. To calculate the lighting load, fluorescent lights/fixtures available in the market were studied. Taking an average product – Sylvania T8, with power rating 58W and 5400 lumens specified by the manufacturer, mounted 2m above the working table effectively lights an area of 12.6m² if the fixture throws light at 90°. It thus produces an average of 428lux in the region (28lux above the required minimum). If the power rating is 58W, then the lighting power density is 58W/12.6m², after rounding is 5W/m². So, for storage, services and BOH areas power density is set at 5W/m², for other spaces a higher value of 6W/m² is set. Power density is set at 10.76W/m² for classrooms and conference rooms, 16.15W/m² for offices and 3.23W/m² for services/storage. Storage, services and other BOH spaces are assumed to be unconditioned, circulation spaces are naturally ventilated, and all other spaces including offices, classrooms, halls etc are conditioned spaces.
These spaces are heated or cooled depending upon the temperature set points. The building is assumed to be 12/5 facility with daily occupancy percentage as specified by the figure below.
Figure 8: Occupancy schedule
Base Case After having set the base model, the location of the place was determined and the local climate of the two sites was analysed. Nottingham has a predominantly cold climate while Singapore has a warm climate. The monthly average temperatures of the two sites were fed into a compu-
ter program, COMZONE, developed by Prof. M Gadi from the University of Nottingham. The program calculates the comfort range of people of that zone. Thus, Nottingham’s range is 17 °C to 23 °C, while Singapore’s is 23 °C to 30 °C.
Figure 9: Nottingham comfort zone [COMZONE]
Figure 10:Singapore comfort zone [COMZONE]
Heating set point for Nottingham is set at 18 °C while for Singapore at 25 °C, similarly cooling set points are at 23 °C and 27 °C respectively. The outdoor air requirement for all cases is 10L/s per person.
Figure 11: Nottingham annual energy
The annual energy intensity for Nottingham is 1923 MJ/m², while for Singapore it is 605 MJ/m². Figure 12: Singapore annual energy
The cooling load for Singapore is more-or-less constant throughout the year with an increase of about 200 kWh during the summer months. The fluctuating cooling demand for Nottingham is due to heat generation within the building and heat gain through the glazing. Heating is required during winters in
Nottingham which decreases in summers, while Singapore has high temperatures throughout the year and needs no heating of the spaces. Heating is a very energy intensive process and thus the total energy consumption follows a similar trend as heating demand, this can be visualized by the graphs.
Figure 13: Energy distribution Nottingham
Figure 14:Energy distribution Singapore
Space Cooling 9000 8000 7000 6000 5000 4000 3000 2000 1000 0
Jan
Feb
Mar
Apr
Nottingham 2397
2260
2028
Singapore
6231
7709
6614
May
Jun
Jul
Aug
Sep
1301
855
1979
3934
1128
7852
8263
7665
7631
8382
Nottingham Table 3: Cooling demand comparison
Singapore
Oct
Nov
Dec
1286
216
1355
1772
6961
7986
7086
6680
Space Heating 120000 100000 80000 60000 40000 20000 0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Nottingham 102428 95447 97127 65267 39026 15468 4941 14195 13411 42722 75140 87905 Singapore
0
0
0
0
0
0
Nottingham
0
0
0
0
0
0
Oct
Nov
Dec
Singapore
Table 4: Heating demand comparison
Total Energy Nottingham
Singapore
1000000
100000
10000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Nottingham 12016 11184 11414 79274 51686 29010 21398 26829 25385 54265 89282 10359 Singapore
20057 18482 21995 21772 22670 21363 21495 22992 20077 22256 20448 19906
Table 5: Total energy comparison
Average Monthly Energy Comparison Nottingham
Singapore
100000
10000
1000
100
Misc Space Ventilati Pumps Equipm Cooling on Fans Aux ent
Area Lights
Ext Usage
Nottingham
3065
562
5232
1709
1327
Singapore
3065
562
5232
7422
3017
Table 6: Average monthly energy usage under different heads
From the comparative graphs, it is evident that HVAC is a major contributor of energy demand, and controlling this factor has a significant impact on the energy distribution. For instance, HVAC contributes to total energy usage in Nottingham and Singapore of approximately 23.8% and 35% respectively. This is followed by lighting demand at 20% and 14% respectively.
Space heat
Hot Water
1578
53507
917
1279
0
549
Improvement Strategies After the base run, an Insight 360° was generated to study factors playing a key role in energy consumption. For Nottingham the energy demand is 256.91 kWh/m²/yr while for Singapore it is 156 kWh/m²/yr. For Nottingham we observe that the sun’s highest position is at 60° and 12° altitude in summer and winter respectively, due south. Being in a relatively cold climate, it will be advantageous to have the office façade face south to have natural daylight as well comfortable heat ga-
both the east and west facades. Heat loss is a major cause of high energy demand as observed by the Insight report. So, the walls, roofs and windows need to be thermally insulated to a degree that prevents heat loss without compromising gain in winters. As suggested by Insight, the walls when insulated by 4” fibre board on either side of concrete, roof if insulated with R15 foam, and windows installed with low-e double/triple glazing will lower the demand by 22.27 kWh/m²/yr. The final energy consumption is reduced to 223.53 kWh/m²/yr and can be read from the graph below.
Figure 15: Nottingham sunpath
In during winter months when the sun is low. This will reduce the heating demand as evident by the curve. Overhangs on southern façade is required to shade the building from high summer sun, as well as by reducing the WWR ratio of
Figure 16: Energy usage vs model changes [Insight], Nottingham
Nottingham Suggested Changes by Insight 360° No#
Factors
0
Original
1 2 3 4 5 6 7 8 9 10 11
Building Orientation Window shade south WWR West Window shade west WWR East Window shade east Wall construction Roof construction Window glass west Window glass east Final model
Modification
Change in Energy (kWh/m²/yr)
Mean Energy (kWh/m²/yr) 256.91
90° anticlockwise 1/6th window height From 75% to 50% 1/3rd window height From 90% to 40% 1/2 window height 14" ICF R15 Double glazing - low E Triple glazing - low E
-0.72 -0.08 -0.24 -0.43 -1.37 -0.08 -8.19 -17.41 -2.43 -2.43 -20.43
256.19 256.11 255.87 255.44 254.07 253.99 245.8 228.39 225.96 223.53 223.53
Table 7: Nottingham model changes
The following steps outline the changes in the model done after analysis: 1. Orientation of the building along the east-west axis, with office block facing south. 2. Reduction of WWR of the new south façade to 50%, and triple glazed low-E windows (Figure 16). 3. Introduction of sun shading louvres as overhangs over southern windows. 4. These louvres are oval shaped metal profile, at an angle of 50° and 250mm spacing.
5. Double glazed windows on the northern façade, which now is the corridor (Figure 17). 6. 600mm projection of roof slab, which helps to reduce heat gain by providing shading for the building mass. 7. Overhang (1/2 H) over all external doors. 8. The external and internal walls are now insulated by 100mm and 80mm EPS panels respectively. 9. Adding thermal insulation layer of 200mm on roof slab. 10. Better insulated curtain wall panels (Figure 24).
Figure 17: Triple glazing detail
Figure 18: Double glazing detail
Figure 19: New south facade in Nottingham
Figure 20:New north facade in Nottingham
Figure 21: Facade isometric
Figure 22: Facade detail
Singapore, located near the equator has a constant climate throughout the year. The sun is usually high in the sky, with maximum altitude of 90° and lowest at 70°. Based on this it is wise to have the building aligned along east-west axis, such that the longitudinal facades do not face west from where the maximum heat gain occurs.
Further, wall and roof types when changed with the new ones having thermal insulation layer, the energy demand falls by 6.67 kWh/m²/yr. The strategies suggested by Insight and the total reduction in energy is shown in the following graph/table.
Figure 24: Energy usage vs model changes [Insight], Singapore Figure 23: Singapore sunpath
This is followed by shading on the south side (2/3rd of window height) and reducing the window-wall ratio of both the east and west facades, to 50% followed by installing solar shades to prevent the high sun. Since this is a hot location it is important that the heat from the building can be dissipated to the environment, this is done by removing the glazing from the corridors. The result is a naturally ventilated circulation space, and the interior conditioned office space is further prevented from solar heat gain.
Singapore Suggested Changes by Insight 360° No# 0 1 2 3 4 5 6 7 8 9 10 11
Factors Original Building Orientation Window shade south WWR West Window shade west WWR East Window shade east Wall construction Roof construction Window glass west Window glass east Final model
Modification
90° either direction 2/3rd window height 50% 2/3rd window height 50% 2/3rdwindow height 12.25" SIP R10 Double glazing - low E Double glazing - low E
Change in Energy (kWh/m²/yr)
Mean Energy (kWh/m²/yr)
-0.82 -0.61 -3.27 -0.92 -0.35 -0.35 -1.04 -5.63 -2.71 -1.78 -9.29
156.47 155.65 155.04 151.77 150.85 150.5 150.15 149.11 143.48 140.77 138.99 129.7
Table 8: Singapore model changes
Based on these recommendations, the following changes were made in the model: 1. Orientation of the building along the east-west axis, with office block facing south. 2. Reduction of WWR of the new south façade to 50%, and triple glazed low-E windows. 3. Introduction of horizontal louvres over glazed part of the office spaces. 4. These louvres are oval shaped metal profile, at an angle of 15° and 120mm spacing. 5. Removing glazing from the new north façade, where the corridor is located, and adding vertical louvres.
6. These louvres are 30mm wide, at 150mm spacing and filter the sunlight to prevent excessive heat gain. 7. These louvres are 30mm wide, at 150mm spacing and filter the sunlight to prevent excessive heat gain. 8. 1.2m overhang over all external doors. 9. 1m projection of roof slab, and introduction of pergolas over the roof. This strategy helps to reduce heat gain by providing shading for the building mass. 10. The external and internal walls are now insulated by 100mm and 80mm EPS panels respectively. 11. 200mm EPS in roof slab.
Figure 25: New insulated external wall
Figure 26: New insulated internal wall
Figure 27: New insulated roof slab
Figure 28: Insulated panels on south facing curtain frame, variable color
Figure 29: Facade isometric view
Figure 31: South facade
Figure 32: North faรงade
Figure 30: Facade detail
Updated Energy Simulation An energy simulation was performed after the necessary changes done on both the models. The new energy demand is shown here in the graph compared to the base model. The m-
onthly average energy under different heads have been plotted and compared against the base case of the two locations separately.
Nottingham Monthly Average Energy Consumption (kWh) Base Model
Updated Model
100000
10000
1000
100 Area Lights
Space Cooling
Ventilatio n Fans
Space heat
Hot Water
Avergae Monthly Energy
Base Model
3065
1709
1327
53507
917
67897
Updated Model
869
663
529
18119
526
22443
Table 9: Nottingham energy comparison
In both cases it has been observed that the energy demand for all energy heads has been reduced, so much so that the energy intensity is now 353 kWh/m²/yr for Nottingham and 213kWh/m²/yr for Singapore.
For HVAC (heating and cooling), the addition of thermal insulation in walls, roofs, and curtain walls have drastically reduced heat gain/loss, as the case may be.
Singapore Monthly Average Energy Consumption (kWh) Base Run
Updated Model
100000
10000
1000
100 Area Lights
Space Cooling
Ventilation Fans
Hot Water
Avergae Monthly Energy
Base Run
3065
7422
3017
549
21126
Updated Model
867
2500
1100
162
6570
Table 10: Singapore energy comparison
The introduction of sunshades, louvres and overhangs have also decreased heat gain in the building, which is reflected by decreased cooling load. Since the building is now better insulated there is reduced heat loss from the water in the plumbing network, hence the energy needed to heat water has also decreased. It is interesting to note that the energy used in area lights has significantly reduced, despite decreased area of opening, leading to lesser naturally lit areas. Figures 35 to 38 show the daylight simulation
before and after. The CIBSE recommended lighting levels for office is between 300-500 lux, which is shown here in cyan color. Values below this are in red, green and yellow are for levels above 500lux, as indicated on the legend. Use of efficient lighting fixtures has significantly reduced energy consumption under this head. The lighting power density is reduced by 1W/m².
Figure 37: Daylight legend in Lux
Figure 33: Nottingham base model daylight
Figure 34: Singapore base model daylight
Figure 35: Nottingham updated model daylight
Figure 36: Singapore updated model daylight
The reduced level of daylight can be attributed to 3 major causes: 1. Earlier the office block faced west and received daylight every afternoon. With this faรงade now facing south, it receives only during certain time of the day. 2. Decrease window area to reduce heat loss/gain. 3. Introduction of shading devices to prevent summer sun from entering, thereby requiring artificial lights.
We can also compare the space heating and cooling load separately
for the two locations, to observe the change in energy demand.
Nottingham Heating Load Comparison 120000 100000 80000 60000 40000 20000 0 Base model
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
102428 95447 97127 65267 39026 15468 4941 14195 13411 42722 75140 87905
Updated model 31800 29421 30158 20822 13841 6968
Base model
2915
6790
6749 15561 24370 28036
Updated model
Table 11: Heating load for base and updated version, Nottingham
Singapore Cooling Load Comparsion 9000 8000 7000 6000 5000 4000 3000 2000 1000 0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
6614
6231
7709
7852
8263
7665
7631
8382
6961
7986
7086
6680
Updated model 2246
2104
2656
2688
2778
2553
2507
2813
2352
2687
2403
2211
Base model
Base model
Updated model
Table 12: Cooling load for base and updated version, Singapore
Similarities and Differences The two locations have a very different climatic condition and have different energy demands in a building. Differences in HVAC is well marked. For Nottingham the annual heating load is 221,098 kWh and cooling load is 7,950 kWh, which can be attributed to seasonal change and internal gains. While the there is no heating demand for Singapore, only cooling load of 30,000kWh annually. The lighting demand for both the base case is same, and so is the demand for the updated model. This reveals that both the location required similar amount of energy for area light if the building parameters are kept same. Similarly, the energy demand under the heads, Misc Equipment, Pumps Aux and Ext Usage, have remained the same for both the cases, revealing that it is independent of location. Ventilation Fans’ energy is double for Singapore as it requires more outside air ventilation to cool. The demand for both these locations have halved in the updated model, revealing that thermally insulated buildings are energy efficient in both warm and cold climates.
The hypothesis is further validated by observing that the HVAC load has decreased 3-folds for both the cases. Thus, what we observe is the ratio of change of energy demand for both Nottingham and Singapore is same.
Figure 38: Nottingham updated building orientation
Figure 39: Singapore updated building orientation
The other important difference is the sun shading design for the two cases. Since the sun is usually high and temperatures hot in Singapore, a continuous blind type horizontal
shading has been provided. In Nottingham, the winter sun is a welcome and hence a horizontal projecting is used to block only the summer sun.
Figure 40: Office building in Nottingham
Figure 41: Office building in Singapore
Further, there can be a reduction in carbon footprint by installing solar PV panels on the building as suggested by Insight, the potential being 186,264 kWh/yr and 397,242 kWh/yr respectively.
Further Recommendations A Further reduction in energy consumption is possible by adopting the following measures: 1.
Installing Solar PV panels PV offers a chance to offset energy consumption form the grid, it does not however, make the building energy efficient. It makes it just grid independent and carbon neutral. A PV potential simulation suggests an annual capacity of 186,264 kWh/yr for Nottingham and 397,242 kWh/yr for Singapore. This is assuming use of 100% roof area for installing PV panels and it more than offsets the annual energy demand of the two building. (Nottingham at 269316 kWh and Singapore at 78840 kWh).
Figure 42: PV 268kWh/m²
energy
for
Singapore,
2. Open floor plan From the lighting analysis it is evident that the cubicles near the window block the natural light from reaching interior spaces. So does walls and other such features. For lighting efficiency, these structures should be either reduced or moved towards the back and large public spaces should be brought near the windows. This will result in higher natural light intensities within the entire depth. 3. Roof light Top floors can also take benefit of natural light from the sky above by installing sky lights. This will help reduce dependency on artificial lights. 4. Renewable potential Other sources of renewable energy include wind, geothermal, small hydro power etc. These can be incorporated during the site planning to harness potentially free sources of energy with varying payback period.
List of Figures
Figure 1: External wall detail, base design...............................................................3 Figure 2: Internal wall detail, base design ...............................................................4 Figure 3: Glazing detail, base design........................................................................4 Figure 4: Mullion detail, on curtain frame ...............................................................4 Figure 5: Floor slab detail ........................................................................................4 Figure 6: Roof slab detail .........................................................................................4 Figure 7: False ceiling detail .....................................................................................5 Figure 8: Occupancy schedule .................................................................................6 Figure 9: Nottingham comfort zone [COMZONE] ....................................................7 Figure 10:Singapore comfort zone [COMZONE] ......................................................7 Figure 11: Nottingham annual energy .....................................................................7 Figure 12: Singapore annual energy ........................................................................7 Figure 13: Energy distribution Nottingham .............................................................8 Figure 14:Energy distribution Singapore .................................................................8 Figure 15: Nottingham sunpath .............................................................................11 Figure 16: Energy usage vs model changes [Insight], Nottingham ........................11 Figure 17: Triple glazing detail ...............................................................................13 Figure 18: Double glazing detail ............................................................................13 Figure 19: New south facade in Nottingham .........................................................13 Figure 20:New north facade in Nottingham ..........................................................13 Figure 21: Facade isometric ...................................................................................14 Figure 22: Facade detail .........................................................................................14 Figure 23: Singapore sunpath ................................................................................15 Figure 24: Energy usage vs model changes [Insight], Singapore ...........................15 Figure 25: New insulated external wall .................................................................17 Figure 26: New insulated internal wall ..................................................................17 Figure 27: New insulated roof slab ........................................................................17 Figure 28: Insulated panels on south facing curtain frame, variable color ...........17 Figure 29: Facade isometric view ..........................................................................18 Figure 30: Facade detail .........................................................................................18 Figure 31: South facade .........................................................................................18
Figure 32: North façade .........................................................................................18 Figure 33: Nottingham base model daylight .........................................................21 Figure 34: Singapore base model daylight .............................................................21 Figure 35: Nottingham updated model daylight ...................................................21 Figure 36: Singapore updated model daylight.......................................................21 Figure 37: Daylight legend in Lux ...........................................................................21 Figure 38: Nottingham updated building orientation ...........................................23 Figure 39: Singapore updated building orientation ...............................................23 Figure 40: Office building in Nottingham ..............................................................24 Figure 41: Office building in Singapore ..................................................................24 Figure 42: PV energy for SIngapore, 268kWh/m² ..................................................25