Jong Hee PAIK
UNIVERSITY OF NOTTINGHAM DEPARTMENT OF ARCHITECTURE AND BUILT ENVIRONMENT
Environmental Performance Modelling (K13EPM) Report
Jong Hee Paik
24th January 2013
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CONTENTS
Page
1
DESCRIPTION OF THE BUILDING AND THE BASE MODEL
1
2
SINGAPORE AND NOTTINGHAM CLIMATE ANALYSIS AND
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STRATEGIES
3
4
5
2.1 Climate of Singapore
3
2.2 Climate of Nottingham
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ANALYSIS OF BASE BUIDLING IN SINGAPORE AND NOTTINGHAM
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3.1 Base model in Singapore
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3.2 Base model in Nottingham
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DESCRIPTION OF UPDATED MODELS
18
4.1 Materials
18
4.2 Building design
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ANALYSIS OF UPDATED BUILDING IN SINGAPORE AND
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NOTTINGHAM 5.1 Updated model in Singapore
21
5.2 Updated model in Nottingham
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6. SIMILARITIES AND DIFFERENCES OF THE DEISGN IN BOTH CLIMATES
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1 DESCRIPTION OF THE BUILDING AND THE BASE MODEL The building is a three storey office building of a rectangular shape. It has dimensions of 54m*18m*15m, and the wider axis of the building lies on the north-south axis. The building has been divided into three zones for the building simulation: the ground floor, first floor and second floor. However they will be analysed as a whole building. The ground floor consists of a reception, many classrooms and a chilled water pump room. The first floor has some classrooms, offices, meeting rooms, reception, and a room with air handling unit. The second floor has a hall, offices and meeting rooms, and AHU room. There are corridors on each storey of the east façade of the building, which provide some shading for the storey below. There are also horizontal shading devices for the windows on the first and second floors on west façade of the building. Figure 1 and 2 represent the 3D model of the building drawn by the Ecotect software. The corridors, shading devices, and the roof have not been included in the zoning used. Moreover, the internal partitions and doors have been omitted for the convenience of the thermal performance analysis on the Ecotect software.
Figure 1.1
Base model 1
Figure 1.2
Base model 2 1
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The base model of the building consists of materials such as 100mm thick dense concrete external walls with gypsum plaster to interior face and 6mm single glazed windows in a timber frame. On top is the 300mm dense concrete slab roof with black bitumen waterproofing membrane which has been assumed to have zero thermal resistance. The roof is not included for the thermal zones, and instead of the roof, the second floor ceiling will be considered as the building envelope. The top ceiling is composed of 300mm concrete. The internal floors have 300mm dense concrete slab with 6mm carpet, and the ground floor is constructed on 1500mm soil. The U-values of each material can be seen from Table 1. Table 1.1
U-values of building materials
Building Parts
External Wall
Window
Internal floor
Ground floor
Top ceiling
U-Value (W/m2K)
3.81
5.1
2.2
0.45
2.82
Further assumptions have been made that 80% of the floor area on each storey of the building is usable office space. Each storey has an occupant density of 10m 2 per person, which makes it 78 people per floor, and they are sedentary. 10l/person/s of fresh air is required and this is supplied via mechanical ventilation system. The building is to be mechanically heated and cooled to the locally acceptable temperatures to provide and maintain thermal comfort for the occupants. It has been also assumed that the building is moderately resistant to infiltration. 90% of the floor area is lit to an average illuminance of 400lux during the office hour. This is achieved by using florescent strip lights. Total of 30W/m2 of lighting and equipment gains are assumed. The office hour is from 8am for 12 hours; all occupants arrive for work at 8am, 50% leave for lunch at 1pm, 60% leave work at 5pm, 20% remain in the building at 6pm, 5% at 7pm and the building is empty at 8pm.
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2 SINGAPORE AND NOTTINGHAM CLIMATE ANALYSIS AND STRATEGIES 2.1 Climate of Singapore Singapore is located near the equator, which classifies its climate as tropical rainforest climate. It does not have distinct seasons through the year, and there is a monsoon season from November to January, which gives abundant rainfall. Table 2.1 shows the summary of overall climate of Singapore Table 2.1
Climate data for Singapore (Source: National Environment Agency)
2.1.1 Temperature The temperature and pressure in Singapore is relatively uniform throughout the year. It can be seen from Table 2.1 that the average lowest and highest temperatures range from 23 to 32°C, with the highest recorded temperature of 36°C in March and the lowest recorded temperature of 19.4°C in January. Figure 2.1 demonstrates the hourly temperature variation (blue line) on an average hottest day and Figure 2.2 for an average coldest day. It can be seen that the temperature difference from day and night is relatively small.
Figure 2.1 Hourly temperature data on an average hottest day (June 10) in Singapore (Source: Ecotect weather tool) 3
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Figure 2.2 Hourly temperature data on an average coldest day (December 7) in Singapore (Source: Ecotect weather tool) 2.1.2 Humidity As Singapore has the tropical climate, it can be concluded to have high humidity. The humidity in Singapore ranges from 60% up to 100%. Table 2.2 shows the mean maximum and minimum monthly relative humidity levels. As shown, the maximum and minimum relative humidity levels are almost the same throughout the year, with the average of 84%. It can also be seen that the RH levels during the monsoon season are slightly higher than other months. This is due to the abundant rainfall in that period. Table 2.2 Mean relative humidity data for Singapore (Source: National Environment Agency)
2.1.3 Solar Radiation Since Singapore is located near the equator, it receives relatively high amounts of the solar radiation. Figure 2.3 illustrates the sun path in Singapore. From Table 2.1, it can be inferred that there are average of 5.5 strong sunshine hours daily, with average insolation of 4.15 kWh/m2. The monthly average of daily solar insolation is given in Table 2.3. The daily solar 4
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insolation varies around 4 to 5 kWh/m2, with the insolation relatively lower during the monsoon season. The total annual insolation gives around 1630 kWh/m 2/year.
Figure 2.3
Sun-path diagram for Singapore (Source: Ecotect weather tool)
Table 2.3 Monthly average daily solar insolation in Singapore (Source:NASA Langley Research Centre Atmospheric Science Data Center)
2.1.4 Wind Singapore does not have a significant windy season, and its wind speed stays relatively small, around 1.75 m/s. Table 2.4 indicates the mean wind direction and daily wind speeds in each month. This shows that similar wind direction, N/NE takes place for winter time, S/SE for summer time, and variable wind directions in spring and autumn times. Figure 2.4 illustrates the all year prevailing wind data illustrating the direction, speed and frequency of the wind in Singapore. 5
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Table 2.4
Singapore wind statistics (Source: National Environment Agency)
Figure 2.4
Annual prevailing winds in Singapore (Source: Ecotect weather tool)
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2.2 Climate of Nottingham Nottingham is located in the East Midlands of England. Its climate is a maritime climate, as most of the Europe, influenced by the North Atlantic Ocean. There are four different seasons, and it does not have a typical dry or wet season as the precipitation is well distributed throughout the year. Table 2.5 shows the summary of overall climate of Nottingham. Table 2.5
Climate data for Nottingham, UK (Source: Met Office)
2.2.1 Temperature One characteristic of moderate climate is that the prevalent temperatures are neither too high nor too low. As seen from Table 2.5, the highest average temperature is in July with 21.3°C and the lowest average temperature is in February with 1°C. Figure 2.5 and 2.6 demonstrate the hourly temperature variation (blue line) on an average hottest day and average coldest day. As it can be seen, the highest temperature does not usually exceed 25°C and the coldest go down to around -5°C.
Figure 2.5 Hourly temperature data on an average hottest day (July 7) in Nottingham (Source: Ecotect weather tool)
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Figure 2.6 Hourly temperature data on an average coldest day (January 15) in Nottingham (Source: Ecotect weather tool) 2.2.2 Humidity East Midland’s average relative humidity levels range from around 60% up to 100%, similar to Singapore. However, unlike Singapore, whose relative humidity levels are almost the same throughout the year, Nottingham’s RH levels differ based on the different seasons. Figure 2.7 illustrates the average daily high and low RH levels. As it can be seen, during the winter season, the lowest RH level is around 80%. The warm currents from the surrounding ocean bring the extensive amounts of humidity.
Figure 2.7 Average daily high and low relative humidity for East Midlands (Source: Weather speak)
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2.2.3 Solar Radiation Unlike Singapore, Nottingham does not have as much sunlight available due to its location. According to Table 2.5, there is average of 3.9 of strong sunshine hours based on the mean monthly values, and only around 2 hours of strong sunlight available during the winter times. Figure 2.3 illustrates the sun path is Nottingham. It can be seen that the sun path over the winter months is much shorter than summer months. Thus the length of the sun affects significantly on the daily insolation. Figure 2.8 shows the average daily insolation for each month in Nottingham. This gives total annual insolation of around 897 kWh/m 2/year.
Figure 2.8
Sun-path diagram for Nottingham (Source: Ecotect weather tool)
Table 2.6
Monthly average daily solar insolation in Nottingham
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2.2.4 Wind Wind is very much available in Nottingham, with the wind speed of 5-6 m/s throughout the year. Table 2.7 indicates the wind direction and average wind speed in each month. The wind direction is from S/SW from August to February, and then varies from March through July. Figure 2.9 demonstrates the all year prevailing wind data showing the direction, speed and frequency of the wind in Nottingham. Table 2.7
Wind statistics for Nottingham, East Midlands
Figure 2.9
Annual prevailing winds in Nottingham (Source: Ecotect weather tool)
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3 ANALYSIS OF BASE BUIDLING IN SINGAPORE AND NOTTINGHAM 3.1 Base model in Singapore The psychrometric chart in Figure 3.1 illustrates the comfort level range in yellow box. The blue dots represent the hourly data points over a year. The red box illustrates the adaptive comfort level range in conditions of natural ventilation. It can be seen from this chart that Singapore’s temperature range is far from the comfort level, and with the natural ventilation, it can cover one third of the discomfort due to hot and humid condition. As mentioned in part 1, the base model of the building is designed to be mechanically heated and cooled to the locally acceptable temperatures. In the case of Singapore, heating is not really necessary, due to its constant high temperatures. Hence full air conditioning has been chosen in the simulation analysis of the building with the Ecotect software. And thermal comfort range has been assumed to be 24-26°C for the office building in Singapore, with 60% relative humidity.
Figure 3.1
Psychrometric chart – Singapore
Due to its climate, a building in Singapore is not likely to have heat losses, but great amount of heat gains. This big amount of heat gains will cause discomfort for the occupants without any mechanical cooling system. Figure 3.2 shows the hourly heat gains on a hottest average day. The coldest days in Singapore are not considered in this paper, because they are not much different from the hottest days. The blue line represents the internal gains, which suddenly increases around 7-8am when the people come to work, as well as the lights and the equipments are turned on for use. Later shows decrease in the heat gains as people go out for lunch or get off work. 11
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Figure 3.2
Hourly heat gains in the base building in Singapore (Hottest average)
Table 3.1 and Figure 3.3 show detailed breakdown of the heat gains and losses of the building. Inter-zonal heat gains/losses were not considered as all three storeys of the building is designed to have the same internal conditions. As can be seen, internal gains take greatest proportion with 58.9%. This is the sensible and latent heat gains from the occupants, lighting, and other equipments. Following are the heat gains from ventilation and fabric; these gains are influenced by the outdoor temperatures. And then there are heat gains from the sun, direct and indirectly. Table 3.1
Breakdown of heat gains of the base building in Singapore GAINS BREAKDOWN - All Visible Thermal Zones FROM: 1st January to 31st December CATEGORY LOSSES GAINS FABRIC 65.60% 10.30% SOL-AIR 0.00% 7.20% SOLAR 0.00% 9.10% VENTILATION 34.40% 14.50% INTERNAL 0.00% 58.90% INTER-ZONAL 0.00% 0.00%
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Figure 3.3
Breakdown of heat gains of the base building in Singapore
Figure 3.4 shows the discomfort degree hours in each month in all zones. It can be seen that half of the times throughout the year are ‘too hot’ in the building in Singapore. Hence accordingly, there must be a cooling system that will even out the heat that causes discomfort in the building. Figure 3.5 shows the amounts of cooling load that is required in each month to eliminate the thermal discomfort in the building. An average of 52,050kWh of cooling is required per month, and 624,608kWh per year.
Figure 3.4
Discomfort degree hours in all zones in the base building in Singapore
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Figure 3.5
Monthly cooling loads in the base building in Singapore
3.2 Base model in Nottingham Unlike Singapore, Nottingham has four seasons, and it will need heating as well. Figure 3.6 shows the psychrometric chart of Nottingham. As mentioned before, the yellow box represents the range of comfort level; the red box represents the comfort level in conditions of natural ventilation; and the blue dots are temperature data over a year. It can be seen that on the contrary of Singapore, Nottingham will need a lot of heating, and mechanical cooling might not be necessary, since it can be dealt with natural ventilation. The thermal comfort range of 22-24°C has been applied in the simulation analysis of the building in Nottingham, with 60% of ideal humidity.
Figure 3.6
Psychrometric chart – Nottingham 14
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In contrast to Singapore, the base model in Nottingham will have both heat gains and losses from and to the outdoor environment; heat gains in summer season and heat losses in the winter season. However, as mentioned before, Nottingham has maritime climate, and it does not have extreme weathers. Especially the summer is not too hot, but warm. As it can be seen in Figure 3.7, the heat gains are not as big, except the internal gains. However, during the cold period, there is a great heat loss compared to heat gains in the summer.
Figure 3.7
Hourly heat gains/losses in the base building in Nottingham (Hottest average)
Figure 3.8
Hourly heat gains/losses in the base building in Nottingham (Coldest average)
Table 3.2 and Figure 3.9 show detailed breakdown of the heat gains and losses of the base building. Internal gains take greatest proportion among the heat gains with 86.2%. Following are the heat gains from the sun. For heat losses, fabric losses through conduction take 59.7% and ventilation with 40.3%. From the Figure 3.9, it can be seen that there are still conduction and ventilation losses during the summer season. This is due to the high internal gains inside the building from the occupants, lighting and equipment gains, thus the inside temperature becomes higher than the outdoor temperature.
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Table 3.2
Breakdown of heat gains/losses of the base building in Nottingham GAINS BREAKDOWN - All Visible Thermal Zones FROM: 1st January to 31st December CATEGORY LOSSES GAINS FABRIC 59.70% 0.00% SOL-AIR 0.00% 7.00% SOLAR 0.00% 6.80% VENTILATION 40.30% 0.10% INTERNAL 0.00% 86.20% INTER-ZONAL 0.00% 0.00%
Figure 3.9
Breakdown of heat gains/losses of the base building in Nottingham
Figure 3.10 shows the discomfort degree hours in each month. It can be seen that among 12 months, more than half of the times are ‘too cold,’ and July and August are the months with warmest temperature. Thus, there should be a mechanical heating all throughout the year, and some extent of cooling may be required during the summer time. Figure 3.11 shows the amounts of cooling and heating load that is required in each month to provide comfort in this building. It has been shown that cooling is only needed for 6months, and heating all throughout the year. An average of 14,690kWh of cooling is required on hottest months, and 22,500kWh of heating is required for each month from October until May. In total, 232,707kWh of energy is needed to provide thermal comfort in this building.
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Figure 3.10
Discomfort degree hours in the base building in Nottingham
Figure 3.11
Monthly cooling loads in the base building in Nottingham
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4 DESCRIPTION OF UPDATED MODELS The base model of the building has been modified to be energy efficient. Due to the climatic difference in Singapore and Nottingham, two different modified designs were produced. However, the same materials of the building have been selected for the designs in both locations. This will give lower U-values, thus minimising fabric gains and losses. In addition, it was evident from Tables 3.1 and 3.2 that the internal gains took the most percentage among heat gains. Unfortunately, internal gains are hard to reduce, since all the lightings, equipments, and the people cannot be removed. The sensible and latent heat from the people definitely cannot be eliminated. The worst case scenario is being considered, so in real life, it won’t always be like we assumed. On the other hand, the heat gains from lighting and equipments can be reduced by using more energy efficient products. Therefore, for the improved models, sensible gain of 20W/m2 has been assumed. Latent heat gain will remain the same, 6W/m2. In addition to the internal gains, infiltration rate has been improved to avoid heat gains and losses. Air change rate and wind sensitivity will be altered to control the infiltration in the building. 4.1 Materials The materials for the base model did not include much of insulation. Insulation of the building materials is essential in reducing the heat transfer through the building envelope. For walls, in addition to the base model material, 25mm of air gap and 50mm of polystyrene foam with high density have been added in between the 100mm dense concrete and 13mm gypsum plaster. The windows used to be single glazed; this has been replaced with triple glazed windows with three 6mm standard glass and 10mm of air gap in between the glasses. The material of the roof will not be changed since it has been assumed to be non-thermal zone. Plasterboards have been added to all ceiling and an air gap, and wool is added in between the concrete and the carpet. For the top ceiling, air gap, wool and plasterboard were added. For the ground floor, 50mm of wool has been added in between concrete and the carpet. Table 4.1 shows the U-values of the newly improved building materials. Table 4.1
Improved U-values of building materials
Building Parts
External Wall
Window
Internal floor
Ground floor
Top ceiling
U-Value (W/m2K)
0.15
1.8
1.04
0.28
1.16
4.2 Building design 4.2.1 Singapore To minimise the direct solar gains, one more layer of horizontal shadings are added to the windows on the first and second floors and three on the ground floor on the west façade, and 18
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the balcony barriers are extended to give more shadings for the storey below. Figure 4.1 and 4.2 demonstrate the improved design of the building.
Figure 4.1
Improved model for Singapore 1
Figure 4.2
Improved model for Singapore 2
4.2.2 Nottingham In contrast to the building in Singapore, it is preferred to maximise the direct solar heat gains to increase the available daylight in Nottingham. This was done by changing the orientation of the building, rotating 90° clockwise, so that the façade with the most windows will be able to capture vast amount of daylight. The horizontal shadings that used to be two for each window on first and second floor, now only has one shading each, as well as the windows on the ground floor. Moreover, windows were added on the other two façades which did not have them before, to let more daylight in. Shadings were not considered since it will only have direct sunlight in the morning and in the evening. 19
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Figure 4.3
Improved model for Nottingham 1
Figure 4.4
Improved model for Nottingham 2
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5 ANALYSIS OF UPDATED BUILDING IN SINGAPORE AND NOTTINGHAM 5.1 Updated model in Singapore For the building in Singapore, in addition to the change of building materials, the infiltration rate has been set to a very small number―air change rate of 0.1ach. This is because the outdoor temperature in Singapore is always hot and humid, thus it is not desired to have much of that air in the building. The internal heat gains still seem very high compared to other factors, shown in Figure 5.1. As mentioned in part 4, this is due to the fact that it is impossible to remove the internal gains totally. However, when compared to the hourly gains for the base building presented in Figure 3.2, the internal gains have decreased by 1/3. Figure 5.2 illustrates the comparison of the hourly heat gains on the average hottest day in Singapore for the base model and improved model.
Figure 5.1
Hourly heat gains in the improved building in Singapore (Hottest average) Hourly heat gains on hottest average day in base and
heat gains (kWh)
400
improved models in Singapore Base building
300
Improved building 200 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hours
Figure 5.2 Comparison of hourly heat gains on average hottest day for base and improved buildings in Singapore 21
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Table 5.1 and Figure 5.3 show the detailed breakdown of the heat gains of the improved building in Singapore. It is evident that the fabric and ventilation heat gains and losses have been decreased significantly, due to the insulation of the materials. Figure 5.3 shows the actual amounts of total heat gains for different months of the year. This can be compared with Figure 3.3 to see that the overall heat gains have decreased from around 400Wh/m2 to 250Wh/m2, by almost 40%. Table 5.1
Breakdown of heat gains of the improved building in Singapore GAINS BREAKDOWN - All Visible Thermal Zones FROM: 1st January to 31st December CATEGORY LOSSES GAINS FABRIC 57.90% 2.70% SOL-AIR 0.00% 0.20% SOLAR 0.00% 8.90% VENTILATION 42.10% 6.50% INTERNAL 0.00% 81.70% INTER-ZONAL 0.00% 0.00%
Figure 5.3
Breakdown of heat gains of the improved building in Singapore
Figure 5.4 below shows the discomfort degree hours in each month for the improved building. This can be compared with Figure 3.4 to see the decrease in the degree hours of discomfort. Figure 5.5 shows the amount of cooling load required in the improved building. Although there have been improvements in the building adding insulation and passive strategies to minimise the cooling load, due to Singapore’s climate and the presence of the internal gains, a cooling system is still needed. It is not advised to use natural ventilation to cool this building, since the outside air is very hot and humid. Figure 5.6 illustrates the new cooling load for each month in the improved building.
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Figure 5.4
Discomfort degree hours in all zones in the improved building in Singapore
Figure 5.5
Monthly cooling loads in the improved building in Singapore
By just looking at the graphs for the cooling loads for the base and improved models, it seems like there is not much change in the cooling load, however, the load has been decreased by significant amount. Figure 5.6 and 5.7 compares the cooling loads in the base building and improved building, monthly and the total. The new cooling load for the improved building is 246,481kWh per year, around 40% of the previous cooling load. This will save great amount of energy.
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Monthly cooling load for the base and improved models in Singapore
60000
Cooling (kWh)
50000 40000 30000 20000 Base model Improved model
10000 0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month
Figure 5.6 Comparison of monthly cooling loads in base and improved models in Singapore Total cooling loads for the base and improved models in Singpaore
Cooling load (kWh)
800000 600000
Total cooling load
400000 200000 0 Base model
Improved model
Figure 5.7 Comparison of the total cooling loads in base and improved models in Singapore 5.2 Updated model in Nottingham Like the improved model in Singapore, it is also evident in the improved building in Nottingham that the fabric gains and losses have decreased significantly through the insulation added in the building fabric. Moreover, internal gains have also been decreased. Unlike Singapore, Nottingham’s outdoor temperature is not too bad, thus for the improved building in Nottingham, air change rate of 0.5ach has been designed to cool down the building and provide fresh air. Figures 5.8 and 5.9 show the hourly heat gains and losses in the improved building on hottest average day and coldest average day. Compared with the Figures 3.7 and 3.8 heat losses through convection have decreased a lot, as well as the ventilation losses in cold days.
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Figure 5.8 Hourly heat gains/losses in the improved building in Nottingham (Hottest average)
Figure 5.9 Hourly heat gains/losses in the improved building in Nottingham (Coldest average) On the other hand, since the building envelope has been redesigned to have more windows and less shading for more available daylight, the amount of solar gain shows an increase on the average hottest day, shown in Figure 5.7. Figures 5.10 and 5.11 compares the hourly heat gains and losses in the base and improved models on hottest and coldest average days in Nottingham. It can be seen that less heat losses and gains lower than the base models due to insulation, and especially during the sunshine hours on cold days the decrease is heat losses is very big since there is more direct solar due to the increase number of windows.
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Heat gains/losses on hottest average day in base
Heat gains/losses (kWh)
200
and improved models in Nottingham
150
Base model Improved model
100 50 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -50
Hour
Figure 5.10 Comparison of hourly heat gains/losses in base and improved buildings on average hottest day in Nottingham
Hourly heat gains/losses on coldest average day in base and improved models in Nottingham
Heat gain/loss (kWh)
0 -50 -100 -150 -200
Base model
-250
Improved
-300
model
-350 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Hour
Figure 5.11 Comparison of hourly heat gains/losses on base and improved models on average coldest day in Nottingham Table 5.2 and Figure 5.12 show the detailed breakdown of the heat gains and losses of the improved building. It can be seen from the table that the percentage of solar gain has increased and there are less heat losses through the fabric. Comparing Figure 5.12 with Figure 3.9, it can be seen that the overall heat gains have decreased from around 320Wh/m 2 to 250Wh/m2, by 22%; and the peak heat losses have been decreased from around 1400Wh/m2 to 400Wh/m2, by 70%.
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Table 5.2
Breakdown of heat gains/losses of the improved building in Nottingham GAINS BREAKDOWN - All Visible Thermal Zones FROM: 1st January to 31st December CATEGORY LOSSES GAINS FABRIC 42.00% 0.00% SOL-AIR 0.00% 0.10% SOLAR 0.00% 11.70% VENTILATION 58.00% 0.00% INTERNAL 0.00% 88.10% INTER-ZONAL 0.00% 0.00%
Figure 5.12
Breakdown of heat gains/losses of the base building in Nottingham
Figure 5.13 shows the discomfort degree hours for the improved building. Compared with Figure 3.10, it can be seen that the degree hours that are ‘too cold’ have been almost eliminated by the good insulation of the building fabric; however, the ‘too hot’ degree hours have been increased significantly, due to more solar gains through the windows. Figure 5.14 shows the monthly heating and cooling load for the improved building in Nottingham. The previous vast amount of heating load has been almost gone, but the cooling load stays similar. This is due to the fact that the internal heat gains cannot be removed.
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Figure 5.13
Discomfort degree hours in the improved building in Nottingham
Figure 5.14
Monthly cooling and heating loads in the improved building in Nottingham
Figure 5.15 compares the monthly heating loads for the base and improved building in Nottingham. It can be seen that the heating load is kept very small throughout the year for the improved building. Figure 5.16 shows the monthly cooling loads for the base and improved building in Nottingham. The cooling loads have been decreased for each month. The total amount of heating and cooling loads for base and improved buildings are shown in comparison in Figure 5.17. It shows that although the yearly cooling load has been increased, the overall load for the improved building has been decreased by more than half. In total, 104,763kWh of heating/cooling load per year is required. This will save great amount of energy.
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Heating/cooling load (kWh)
Monthly heating loads for base and improved
Figure 5.15
models in Nottingham
40000
Base model
30000
Improved model
20000 10000 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months
Comparison of monthly heating loads in base and improved models in Nottingham
Heating/cooling load (kWh)
Monthly cooling loads for base and
Figure 5.16
20000
improved models in Nottingham Base model Improved…
15000 10000 5000 0 Jan Feb Mar Apr
Jun Jul Sep Oct Months
Dec
Comparison of monthly cooling loads in base and improved models in Nottingham Total heating/cooling loads for base and 300000
improved models in Nottingham Base model
(kWh)
200000
Improved model
100000
0 Heating load Cooling load
Total load
Figure 5.17 Comparison of total heating loads, cooling loads and heating+cooling loads in base and improved models in Nottingham
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6 SIMILARITIES AND DIFFERENCES OF THE DEISGN IN BOTH CLIMATES The base model has been designed with the potential of being built in Singapore and Nottingham, UK. The base model of the building will work in both locations. However, it has poor selection of building materials, which gives quite high U values, and will need great amount of energy to provide comfort for the occupants in the building. Since Singapore and Nottingham have very different climates due to their geographical locations. Singapore’s hot and humid climate will require cooling all through the year; on the other hand, Nottingham’s maritime will require heating during the winter time, and cooling during the summer time. The base model was first improved by adding insulations on the designed materials. Air cavities and polystyrene foam were added for the walls, the windows were triple glazed, air gap and wool insulation and plasterboards were added to internal floors/ceilings, and wool was added for the ground floor. By adding insulations, it gives much lower U values for the materials, which reduces the heat gains and losses through the building envelope. Thus, conserving energy. In addition, some factors that cause internal gains were altered. For instance, it was assumed that more energy efficient lighting and equipment will be used, and air change rate and wind sensitivity were altered to control the infiltration in the building. These measures were considered for both of the building in Singapore and Nottingham. This is due to the fact that energy saving measures apply everywhere regardless of the geographic location. The insulations added on the building materials and less infiltration in the building will decrease significant amount of heat gains and losses. For the building envelope designs, the model in Singapore needed to avoid solar gains as much as possible. Thus more shadings were added to the windows on both facades. On the other hand, it would be good to increase the direct solar heat gains to improve daylighting in Nottingham, since there aren’t as much sunshine available in the UK. Hence, the orientation of the building has been changed to gain maximum sunlight, and some shadings were removed and more windows were added. This increased the amount of solar gains, but further had an impact on decreasing heating load in winter period. The insulation and control of infiltration decreased the heat gains and losses of the building significantly, which further decreased the amount of heating and cooling loads. Moreover, some building envelope designs were modified to minimise/maximise the solar gains. These updated models showed significant changes on the thermal performances of the both buildings. By updating the base models, the energy required to provide thermal comfort in the building has been decreased by almost half.
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