CENTRAL ST. GILES 1 St Giles High St, London Borough of Camden, London WC2H 8AG, U.K.
AA + EE Environmental & Energy Studies Programme
Architectural Association School of Architecture
Msc / MArch. Sustainable Environmental Design
2011 - 12
Term 1 : Building Study
RODOLFO PEDRO AUGSPACH
MEITAL BEN DAYAN
JOAO PINTO DE OLIVEIRA COTTA
Rodolfo Pedro Augspach would like to acknowledge the Architectural Association School of Architecture for the bursary he was awarded to attend the A.A. S.E.D. MArch course 2011-2012. Meital Ben Dayan would like to acknowledge the Architectural Association School of Architecture for the bursary he was awarded to attend the A.A. S.E.D. Msc course 2011-2012. The entire team would also like to thank the entire SED teaching staff for their support throughout the course. Special Thanks are also attributed to:
David Gilpin (ARUP) James Thonger (ARUP) Mauritz Van der Staay (RPBW) Azeem Ahmad (Resident) Carmel Burke (Resident)
For their personal contributions to this research.
TABLE OF CONTENTS:
1 - INTRODUCTION & SUMMARY
2 - OVERVIEW
3 - OUTDOOR STUDIES
4 - INDOOR STUDIES - APARTMENTS
5 - CONCLUSIONS
6 - REFERENCES
INTRODUCTION The main highlight of this project case study is to investigate and establish an understanding of the environmental design principles of a building and its effects on the urban activity and environmental quality in and around it. This process was further strengthened and supported with the help of weekly lectures, tutorials and workshops. Subsequently, the use of computer tools and published literature on environmental analysis was extensively referred. The building undertaken for the study is Central St. Giles, situated in central London falling under the Camden council. There are several reasons for the choice of this building as focus for the research project, one being the mixed use elements of the building ranging from residences, restaurants, offices and the piazza. Another reason is its central location amidst other prominent public spaces in its immediate vicinity. The architectural office for this development was none other than the Renzo Piano Building Workshop and the engineers in charge were Ove Arup & partners. This further augmented our interest in studying the environmental principles and impact of the building. The building has also received an â€˜Excellentâ€™ rating from the Building Research Establishment Environmental Assessment Method (BREEAM 2004). This as well was an issue that intrigued the team. The process started with investigating published literature, establishing communication with the design architects, the local architects and then finally, the building engineers. The next stage was to obtain the drawings and conduct field measurements and occupant questionnaires within the piazza. At this stage, measurements were taken across the courtyard over several points that were marked on a grid. Six measurements were taken on different weather conditions over the same points, at the same time periods. This data was then reviewed and analysed which pushed for an investigation of the outdoor environmental conditions and occupant comfort in the piazza. Simultaneously the team was trying to arrange for meetings and interviews with the architects, engineers and facility managers to gather information and access to the residences and offices. The group decided to investigate and pursue the offices as part of the indoor studies primarily due to its dense mass and deep plan but unfortunately access to these was not granted. After a persistent attempt the team had managed to get access to two apartments, one facing the North and the other facing the South, thus the indoor studies were focussed within these apartments. This followed with spot measurements in the two apartments accompanied by leaving data loggers over a week strategically positioned within the apartment. The data loggers provided with recordings of temperature over a sustained, prolonged period. As time went by, an opportunity opened to meet with two engineers involved with the project, Mr. David Gilpin and Mr. James Thonger, from Ove Arup & Partners headquartered in London. This was then immediately followed by an interview with the project architect in charge, Mr. Mauritz van der Staay in the Renzo Piano Building Workshop office in Paris. The analysis of all the findings was undertaken as a group to have a collective understanding of the investigation and then later broadly divided into two parts, the outdoor and the indoor study. The outdoor study was focussed on the Urban and Piazza context by Nikhil Deotarase and Peter Augspach, whilst the indoor study comprised two apartments, North facing and South facing, by Meital Ben Dayan and Joao Cotta.
OVERVIEW RUSSELL SQUARE
BRITISH MUSEUM BLOOMSBURY SQUARE
CENTRAL ST. GILES
SOHO SQUARE LOCATION The Central St. Giles is geographically located in a central part of London falling under the Camden City Council and has a Latitude of 51°30’57.28”N and a Longitude of 0°07’39.82”W. It sits right in the heart of the St. Giles district beside the 18th century parish church. The building is positioned almost as a crossroad between other active destinations in its immediate vicinity and is set behind the tall 1960’s office tower, Centrepoint. It also yields numerous links and connections to neighbouring destinations that have traditionally been well known and are part of the public realm. All these are in close proximity to each other, at a walking distance of about 0.5 Km from the Central St. Giles site. These characteristic neighbouring public destinations are illustrated in Figure 1.
Its strategic position and relationship to important arteries like Tottenham Court road, Oxford Street, Shaftesbury Avenue and Bloomsbury Street encourage pedestrian movement right through the site. The building lies amongst busy streets namely the Earnshaw street, St. Giles high street and the Bucknall Street that link and generate a connection to these arteries.
Figure 1 : Satelite Image Showing Central St. Giles with respect to Key Neighboring Public Destinations Source: After Google Earth Page 2
CENTRAL ST. GILES CENTRAL ST. GILES
KENSINGTON / CHELSEA WEATHER STATION
KENSINGTON &CHELSEA WEATHER STATION WEATHER DATA Figure 2: Image Showing the Relation Between Central St. Giles and the Kensington / Chelsea Weather Station in London Source: After Google Earth
Weather data was collected from the Kensinsgton / Chelsea weather station located at approximately 5.5km from the Central St. Giles as shown in Figure 2. The readings for the respective days of our field measurements were obtained from the weather underground website (http://www.wunderground.com). For all other simulations a weather file was generated with Meteonorm 6.1 using the weather data from the Kensington / Chelsea weather station in London which had collected the readings for a 10 year period ranging from 1996 to 2005. Figure 3, shows the mean temperature for this weather data along with the Global radiation decomposed into Direct and Diffused radiation. This will be the source of data for all future references to weather data, unless otherwise noted. COMFORT BAND For the purposes of this research, all comfort bands and zones are calculated using De Dearâ€™s equation, taught in the MArch/Msc programme of Environmental Energy Studies at the Architectural Association. The equation is here presented: Tn= 17.8 + 0.31 Tm
Global Solar Radiation Direct Solar Radiation
where, Tn = Comfort temperature as per De Dear Tm = Monthly mean temperature A comfort band is then plotted using a +- 2.5 K difference for 90 per cent acceptability and a +- 3.5 K difference for 80 per cent acceptability.
Figure 3: Graph Showing Monthly Diurnal Temperature and Solar radiation Averages, Decomposed into Direct and Diffused Radiation Source : After Kensington and Chelsea Weather Station in London generated with Weather tool 2011 Page 3
PRESENT DAY - EXISTING BUILDING Central St. Giles is far denser than the previous building that was on site, as seen in figures 5 and 8. Hence one of the architects challenge was to make the building significantly bigger and shed the negative vibe the previous building reflected in a district as thriving as this one.
OFFICES AFFORDABLE HOUSING
The building, seen in figure 4, is a mixed use development and comprises the following: Office space totalling to 408,000 ft2 10 Restaurant totalling to 25,000 ft2 Roof Terraces totalling to 17,000 ft2 A total of 109 apartments of which 53 are designated as affordable housing The prime idea was to rejuvenate the area from the gloomy St. Giles court that stood there before, as seen on figure 7, in an area with surrounding neighbourhoods that are thriving and are publicly accessed. This regeneration of the St. Giles area falling under the Camden council was a proposed development of the London Plan set by the Mayor of London. The Central St. Giles proposal received opposition from the local resident groups concerned about the over development of the site and putting a strain on the local transport.
Figure 4: The Existing Central St. Giles Project by Renzo Piano Buildng Workshop wiht itâ€™s Programme Distribution Source: After Google Earth
There are 5 public access points to enter the courtyard positioned such that they enhance the transient flow of pedestrians. These openings are oriented such that they act as an extension and form a relationship between the courtyard and the active neighbouring public spaces. Most of the mechanical plant services are situated in the basement as they presented a challenge for the architects. A structure was specifically designed to overhang the basement due to the proposed Crossrail tunnel network. The car parking in the basement holds 33 cars and is accessed by a car lift positioned in the North East part of the site. The loading bay and service delivery areas are also situated in this segment. After conducting interviews and interacting with the architects several design intentions and concepts were revealed, that shape the building the way it is at present: - To bridge the active neighbouring areas like Covent Garden, British Museum, Tottenham court road station, Centrepoint tower and Soho with each other and at the same time making the St. Giles area as a destination within itself - To fragment the big mass in order to reduce the appearance of a high dense mass in this thriving neighbourhood by initiating in a process of putting all the requirements and carving out as per the light path.
Figure 5: The Existing Central St. Giles Project by Renzo Piano Buildng Workshop Source: After Google Earth
- To maintain a transparent ground level, allowing visual permeability from the street into the piazza. This was done by offering the ground level to restaurants and with the use of 6m clear glass on the envelope of the restaurants. For this sole purpose, closed kitchens were not allowed, and if needed had to be moved to the basement level. - To react to the surrounding brick textured buildings while adding quality to the facade that is durable over a long period of time. This was achieved by the use of glazed terra cotta tiles and a punched hole window system as opposed to a fully glazed facade - To reflect even distribution of light in the piazza and into the offices. This was addressed by the use of grey coloured glazed terra cotta tiles as the interior facade overlooking the piazza. Figure 6: Pictures of the existing Central St. Giles Page 4
Figure 7: The previous St. Giles Court in its surrounding Source: After Bing Maps
HISTORY - PREVIOUS BUILDING Up until 2006 another building existed on the site called St. Giles court. It was an office development occupied by the Ministry of Defence that was built during the 1950’s. The building was vacated in 2005 since the Ministry of Defence was undergoing a reduction in all the estates it owned. Figure 8: The previous St Giles Court in its surrounding Source: After Bing Maps
It was a brick building shaped in the form of an ‘S’ resulting in the formation of two courtyards within the building. It comprised of offices for the Ministry of Defence and rose to 8 stories. It offered dead facades to the surrounding buildings and obstructing the urban fabric in a locality surrounding flourishing neighbourhoods like Covent Garden, Holborn, Bloomsbury, Soho and the British Museum. Historically in the 18th and 19th century, St. Giles represented a criminal and notorious locality with sordid slums being inhabited by the poor. The St. Giles Court, that occupied the site for little more than 50 years reflected a dull and gloomy appeal and was described as “a kind of fortress” by Renzo Piano and “a bunker” by Morris Van Der Staay, the project architect.
Figure 9: Pictures of the St Giles Court
The two courtyards to this building were impermeable and were denied public access. They were allowed to be used and served by the building’s tenants and were impervious due to the tall fences all along the boundary of the site closing the building and isolating the complex from the urban fabric. This generated a clump of building mass in the urban context preventing any sort of pedestrian flow in a surrounding neighbourhood which is very active. Page 5
OUTDOOR STUDIES Legend <23°C 22°C - 23°C 21°C - 22°C 20°C - 21°C 19°C - 20°C 18°C - 19°C 17°C - 18°C 16°C - 17°C 15°C - 16°C 14°C - 15°C 13°C - 14°C
Legend 7.0 - 8.0 m/s 6.0 - 7.0 m/s 5.0 - 6.0 m/s 4.0 - 5.0 m/s 3.0 - 4.0 m/s 2.0 - 3.0 m/s 1.0 - 2.0 m/s 0.0 - 1.0 m/s
FIELD STUDIES The team embarked on field measurements first of the outdoor spaces within the building complex that included the courtyard and the outer periphery of the building. To carry out the measurements, several points were marked with the help of a grid superimposed on the building plan. A total of 6 measurements were taken over a period of days and the readings were noted down for each of the selected points marked on the grid. The readings were intentionally taken over 6 different days with varying weather conditions, if not drastic there were slight variations in the weather conditions. These filed studies include the measurement of air velocity, air temperature, surface temperature, sound levels and illumination. In order to better understand the site, a comparison has been made between a cloudy day (October 7th) and a sunny one (October 14th)
First Measurement 07 October 2011 - 12:30 pm Weather Data Temperature: 14 °C Humidity: 67% Wind Direction: West North West Wind Speed: 5.1 m/s Weather Condition: Cloudy
A wind tunnel has been detected in the north eastern entrance to the courtyard in figure 10, but when wind blows from the opposite direction this tunnel disappears, as seen in figure 14. What can be detected however is that the courtyard receives less wind speeds in comparison to the openings and the surrounding streets. Except for the wind spot measurements plan, figure 10, all the other parameters seem not to vary too much in comparison to one spot or the other, except logically in the entrances to the courtyards which receive less light with respect to the rest of the courtyard. Page 6
Figure 10: October 7th Wind Spot Measurements
Figure 11: October 7th Surface Temperature Spot Measurements Legend 60> kLux 40 - 60 kLux 20 - 40 kLux 7 - 20 kLux 6 - 7 kLux 5 - 6 kLux 4 - 5 kLux 3 - 4 kLux 2 - 3 kLux 1 - 2 kLux 0 - 1 kLux
Legend <21°C 20°C - 21°C 19°C - 20°C 18°C - 19°C 17°C - 18°C 16°C - 17°C 15°C - 16°C 14°C - 15°C 13°C - 14°C
Figure 12: October 7th Air Temperature Spor Measurements
Figure 13: October 7th Lux Spot Measurements
Legend 7.0 - 8.0 m/s 6.0 - 7.0 m/s 5.0 - 6.0 m/s 4.0 - 5.0 m/s 3.0 - 4.0 m/s 2.0 - 3.0 m/s 1.0 - 2.0 m/s 0.0 - 1.0 m/s
Legend <23°C 22°C - 23°C 21°C - 22°C 20°C - 21°C 19°C - 20°C 18°C - 19°C 17°C - 18°C 16°C - 17°C 15°C - 16°C 14°C - 15°C 13°C - 14°C
Fourth Measurement 14 October 2011 - 12:30 pm Figure 14: October 14th Wind Spot Measurement
Figure 15: October 14th Surface Temperature Spot Measurements Legend <21°C 20°C - 21°C 19°C - 20°C 18°C - 19°C 17°C - 18°C 16°C - 17°C 15°C - 16°C 14°C - 15°C 13°C - 14°C
Legend 60> kLux 40 - 60 kLux 20 - 40 kLux 7 - 20 kLux 6 - 7 kLux 5 - 6 kLux 4 - 5 kLux 3 - 4 kLux 2 - 3 kLux 1 - 2 kLux 0 - 1 kLux
Weather Data Temperature: 16 °C Humidity: 48% Wind Direction: East Wind Speed: 5.1 m/s Weather Condition: Clear
When looking at the spot measurements of a sunny day, the impact of the sun on the site can be really assessed. A vivid observation here is the rise in surface temperature on a sunny day as opposed to on a cloudy day where the impact of the exposed sun is clearly noticeable in contrast to the unexposed areas. On the cloudy day an almost equal surface temperature was observed ranging from 13.8°C to 15.6°C as seen in figure 11. Whereas on the clear sky day the variation in surface temperature ranges from 13.4°C to 23.1°C (figure 15).
Figure 16: October 6th Air Temperature Spot Measurements
Figure 17: October 14th Lux Spot Measurements
This contrast is even sharper when looking at the illumination levels on the respective points of the site for the 1st and 4th measurements. In the day with a sunny condition, not only did the lux levels increase in exposed areas, but they also decreased in the unexposed areas, further augmenting the contrast. Page 7
25-30 Years old Jacket & Trousers Walking Draughty Too cold Actual P.E.T.: 14.4
25-30 Years old Pullover & Trousers Standing relaxed Draughty Just comfortable Actual P.E.T.: 14.3
35-40 Years old Business suit Standing relaxed Draughty Comfortably cool Actual P.E.T.: 17.1
PHYSIOCLOGICAL EQUIVALENT TEMPERATURE After taking spot measurements on the site a mean Physiological Estimated Temperature (PET) for each spot was calculated, and a PET plan has been drafted (figure 18). The parameters used to generate the values were the mean collected values through the spot measurements. Being that so, this plan allows does not intend to determine which areas are “comfortable”, but rather, establish which areas are more comfortable than others. Throughout those 6 measurements interviews were carried out questioning passers-by and by-standers. Note was taken of what they were wearing in order to determine a clo value, the same is true for age and gender. They were also asked how they felt, and as a comparison, an actual individual P.E.T. was calculated for each of the subjects, using the software RAYMAN. One of the first things noticed is that their actual feeling follows closely to the P.E.T. calculated for each of them, but although it is higher where the plan suggests it should be higher, they do not match it. These discrepancies could be because when it is relatively cold, the wind starts to have a much higher influence, so a 0.5 m/s difference in air speed could mean as much as a 2.4 K difference, as seen in the section in figure 19. On closer observation to the people’s reply as to how they felt, another discrepancy was uncovered towards the north east, where a 26 year old man who feels “just comfortable” with a calculated P.E.T value of 14.3°C, which is more than a 5 k difference with the calculated comfort zone. This could be for one of two reasons, either he just walked there from a more sunny area where his PET would have been 18.2°C and he still feels this, or he just feels comfortable in colder environments. Page 8
Legend 19.6°C - 24.6°C (Comfort Zone)
25-30 Years old Pullover & trousers Walking Too windy Too Cold Actual P.E.T.: 9.0
20-25 Years old Jacket & trousers Sitting - Passive work Draughty Comfortably Cool Actual P.E.T.: 17.0
Figure 18: Plan Illustrating the Physiological Estimated Temperature for Each point that was Measured During the Field Studies.
>60 Years old Jacket & trousers Sitting - Passive work Draughty Comfortably Cool Actual P.E.T.: 17.1
16.0°C - 18.0°C 14.0°C - 16.0°C 12.0°C - 14.0°C 10.0°C - 12.0°C Points of investigation
Legend Air Speed P.E.T. Comfort Zone 19.6°C - 24.6°C Points of Investigation
Figure 19 shows a cross section through the courtyard and below a graph with the plotted P.E.T. along with the calculated comfort band for the month of October using De Dear’s equation for 90% acceptability. The air speed is marked on the right of the graph and this allows us to determine how susceptible the P.E.T. is in respect to the wind speed. The temperature was 15°C and see the solar exposure on each point in is depicted in the bar below. At point two a rise in the P.E.T. in comparison to point 1 can be detected due to the decrease in air speed. There is a further increase towards point three even though the air speed is still increasing. This is because of exposure to direct solar radiation, in fact, at this point, if air speed would have also been 0.5 m/s, the P.E.T. would have been as high as 18°C, which would be in the 80% acceptability comfort band. Finally at point four, we can see a significant drop in the P.E.T. due to the lack of solar exposure and the increase in air speed. This effect is only logical, but the degree of the effect is quite surprising due to it’s magnitude when air speed is only 2.0 m/s. Figure 19: Section depiciting the Physiological Estimated Temperature for each point that were measured during the field studies
Legend 5.5 m/s 5.0 m/s
21 October 2011 - 14:00 pm
4.5 m/s 4.0 m/s
Weather Data Temperature: 14 째C Humidity: 59% Wind Direction: South West Wind Speed: 5.7 m/s Weather Condition: Cloudy
3.5 m/s 3.0 m/s 2.5 m/s 2.0 m/s 1.5 m/s 1.0 m/s 0.5 m/s
Figure 20: Plan Showing the Wind Speed Measurements during one of the Field Studies
WIND STUDIES One of the first few parameters to investigate on the urban level and immediate surroundings of the Central St. Giles was to examine the influence and impact of wind on the building. An important aspect in this particular case was to consider the influence of the 117m tall office tower, known as Centrepoint, that stands on the eastern edge of Central St. Giles at a distance of 70m. Figure 20 Illustrates the pattern and wind speeds experienced during the spot measurements at the pedestrian level. During this field study it was difficult to determine and conclude the influence and hence this aspect continued to raise an interest with the team.
m/s 4.0 3.0 2.0 1.0
Figure 21: Section Showing the Wind Speed Measurements during one of the Field Studies Page 10
Legend m/s 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
South West Wind Direction
WIND STUDIES To understand the influence on Central St. Giles with respect to the neighbouring tall tower, simulations and runs were carried out. The first step was to model the immediate surroundings of Central St. Giles with Centrepoint in Ecotect and run simulations in Winair. Simulations were carried out for the predominant wind directions, namely Southwest, West and South, obtained from Meteornorm. To derive and understand the influence, a comparison was made between two simulations. The first simulation was carried out with the presence of Centrepoint while the second was simulated in its absence. These runs were plotted for the respective wind conditions at 1.5m above the ground, at the pedestrian level. West Wind Direction At the top of figure 22 the results for the most predominant wind direction, the Southwest wind, can be see. The Earnshaw Street on the eastern edge of Central St. Giles shows a reasonable increase in wind speeds in the presence of Centrepoint. The outcomes for western winds are seen in the middle of the figure, this is the second most dominant wind direction. A clear observation here is that the southern street, St. Giles High street, experiences greater wind speeds in the absence of Centrepoint. This occurs due to the parallel direction of the air flow to the street and the absence of any wind turbulence that is caused by the tall tower. While at the bottom of the figure 22 one can see the results for southern winds, no major difference is seen other than the presence and absence of wind turbulence around Centrepoint.
South Wind Direction Figure 22: Computer Fluid Dynamics done with WinAir Testing Centerpointâ€™s Influence on the Site
The result of these simulations highlight that there seems to be no prominent impact of Centrepoint on the surrounding streets or within the courtyard of Central St. Giles. However with the westerly winds the tall tower offers little protection on the leeward side at the pedestrian level to the surrounding streets of Central St. Giles due to wind turbulence generated on the windward side of the tall tower. Page 11
Figure 23: Section Showing the Potential Passive Zone in the Current Building
BUILDING ANALYSIS One of the important issues that caught the teamâ€™s attention regarding the present scheme was the density and distribution of the building mass. An immediate observation was that almost 90% of the building footprint comprises areas with air-conditioned spaces. This brought forward the question whether the use of air conditioning was justifiable in London with average temperatures being low. The air-conditioned spaces include the entire office block, the restaurants and the private housing block. The only free running space of the entire scheme, a mere 10% of the building footprint, is the affordable housing block situated on the North West corner of the site. The team realised that the area of the overall air-conditioned spaces leads to a dramatic increase in energy use. This further encouraged the team to investigate the potential of identifying the passive zones within the building. This would then highlight the areas which could be free running and if required those that could be air conditioned. Figure 23 and figure 24 illustrate the depth of the passive zones that are measured as two times the height from the floor to the ceiling. This results in a potential passive zone with a depth of 4.8m for the private housing and 5.8m for the office block, starting from the edge of the floor plate. What can be observed clearly is that the office plan, measuring 40m in depth, has a potential of having passive areas that account to 47% of the floor area on the periphery of the floor plate.
Nucleus/Core Potential Passive Zone
However for the private housing located on the south west portion of the site the potential for having a free running environment is higher, this obviously is a result of the narrow plan measuring 23m across from the edges of the floor plate. In this case 71% of the floor area has the potential of a passive zone. Page 12
Figure 24: Plan Showing the Potential Passive Zone in the Current Building
Legend Lux 90000 + 81000 72000 63000 54000 45000 38000 27000 18000 9000 10
Conditions Summer Solstice 21st June 12:00 pm Sunny Sky
BUILDING ANALYSIS Another area of research was to study the impact of the current scheme to its immediate neighbouring streets. A comparison was done between the previous and present building as an approach to understand the influence and change Central St. Giles brought to the surrounding streets. Figures 25 and 26 show illuminance levels simulated with the help of Radiance and Ecotect at a height of 1.5m from the ground level for both the previous and current schemes respectively. Both the simulations were carried at a specified date, time and a clear sky condition. A vivid observation here is the drastic impact on the northern street where the current building allows for extremely low values of light penetration as opposed to the previous building. Primarily this is due to the higher density of the current building and clearly shows a strong impact in illuminance levels achieved at the pedestrian level.
Figure 25: Lux levels for the old scheme. The simulation was carried out using Radiance and Ecotect.
Figure 26: Lux levels for the present scheme. The simulation was carried out using Radiance and Ecotect.
The building stands amidst a very busy network of roads, those that experience heavy traffic through all times of the day. This encouraged a research agenda to investigate the sound and noise levels from the adjoining street followed by the impact of this within the courtyard. Page 13
Spring Equinox 21st March
Summer Solstice 21st June
Winter Solstice 21st December
SUN PATH To understand the impact and behaviour of the sun in respect to the building and its immediate surroundings the sun path was plotted with the neighbouring buildings. Figure 27 illustrates the sun path for the spring equinox, summer solstice and winter solstice for particularly three hours of the day namely 9am, 12pm and 3pm. Clearly we see the building casts shadows on the facades of the neighbouring buildings on the northern side. This is observed in almost all the cases except for the summer solstice at 3pm and with less intensity in the spring equinox during the same hour. Similarly the street on the Eastern edge of the site experiences the same in all the three situations. Page 14
Figure 27: Sun Path showing the Overshadowing cast by the New building in the urban Surrounding
Winter Solstice 21st December 12:00 pm Overcast Sky (3000 Lux)
West Facing Elevation A
South Facing Elevation B
1040 Lux 2140 Lux
East Facing Elevation C
Summer Solstice 21st June 12:00 pm Sunny Sky
West Facing Elevation A
Legend Lux 2800 + 2580 2360 2140 1920
13600 Lux 16000 Lux
South Facing Elevation B
One of the research agendas was to further investigate and understand the impact of the current scheme in respect to illumination levels received by the neighbouring buildings. This was dealt by comparing the illuminance levels permitted with two scenarios, one in the presence of the previous building and the other in the presence of Central St. Giles. Simulations were done with the help of Radiance and Ecotect on the three elevations, namely the West, South and East facing facades of the neighbouring buildings. Figure 28 shows the illuminance levels with the two buildings for the summer solstice and the winter solstice. An aspect to take notice here in the case of the summer solstice for the west and south facing facades are the varying difference in levels of illuminance. The previous building permitted values ranging from 20800 lux to 28000 lux as opposed to lower levels ranging from 4000 lux to 18400 lux in the case of the existing Central St. Giles. Evidently, only the upper windows receive higher illumination levels than the lower ones in the current scheme, the reason being due to its higher density.
1260 1040 820 600
East Facing Elevation C
Figure 28: Image showing the lux levels on the adjacent facades for the current and previous building
The simulations done for the winter solstice does not really show an emphatic difference, this being due to the overcast sky condition. However what needs to be observed here is that there is a marginal difference in the illumination levels. This further confirms that the existing scheme permits lesser illumination levels. Page 15
Winter Solstice 21st December 12:00 pm Overcast Sky (3000 Lux)
Reflectance Value Terracotta Tile Facade: 66%
COURTYARD REFLECTANCE One of the architectâ€™s intentions state that the central courtyard had to maintain visual comfort and this was achieved by using a grey coloured glazed terracotta tile cladding for the inner facade overlooking the courtyard. This further interested the team and gave rise to investigate the courtyard in respect to illumination at the floor level. The approach taken here was by comparing the existing facade with a red brick facade similar to the neighbouring brick buildings while maintaining the same window areas of the existing facade. These simulations were done using Radiance and Ecotect with the appropriate reflectance values of the respective materials. Figure 30 illustrates the results for the Winter solstice at 12pm for an overcast sky condition. The illumination levels in the courtyard overlooked by the glazed terracotta tile range from 1280 lux to 2000 lux. Whereas in the case of the brick cladded facade, the range varies from 920 lux to 1460 lux. Clearly we see the terracotta tile does offer higher illumination levels in the courtyard due to its higher reflectance values as opposed to the brick cladding with a lower reflectance value. Page 16
Reflectance Value Brick Cladding Facade: 16% Lux 2000 + 1820 1640 1460 1280 1100 920 740 560 380 200
Figure 30: Plan showing the effect of the different facade materials and finishes for the winter solstice
Summer Solstice 21st June 12:00 pm Sunny Sky
Reflectance Value Terracotta Tile Facade: 66%
Reflectance Value Brick Cladding Facade: 16% Lux 20000 + 18150 16300
14450 12600 10750 8900 7050 5200 3350
Figure 31 illustrates the results for the Summer solstice at 12pm. This being the summer the lux levels observed are generally higher due to the direct sunlight approaching a particular portion of the courtyard. In the case of the terracotta tile the illumination levels vary from 5200 lux to 16300 lux. Whereas with brick cladding the range varies from 1500 lux to 7050 lux. Here we see a similar situation as observed in the case of winter. This further confirms that the grey coloured glazed terracotta tile does offer higher illumination levels distributed evenly across the courtyard.
Figure 31: Plan showing the effect of the different facade materials and finishes for the summer solstice
Figure 33: sky view factor from reference point with the overlay of the Sunpath at Hour 13:00 throughout the year
Figure 35: Summer Solstice sun path for hours 12:00-14:00 with the point from where the sky view factor for figure 33 was taken
COURTYARD STUDIES One of the first things the team learnt after meeting with the designer in charge from Renzo Pianoâ€™s Building Workshop was that the project got itâ€™s form as a result of a massing and carving process seen in figure 32. The first carving was along the perimeter which was purely a formal approach aimed at deconstructing the mass and make the building look as if it where made up of many fragments instead of being one big block. The second carving was to create the square. It is of a rather small size, but the building itself provides protection to the square from the high decibel levels and the winds as we will see further on in the report.
The third carving served to communicate Central St. Giles with the St. Giles Church. This last carving was done in such a way that it allows for direct solar radiation to hit the courtyard every day of the year during midday.
Since this courtyard is surrounded by restaurants, as seen in Figure 34, the team immediately tested the potential of using the space during lunch hours throughout the year. This was also prompted by the suggestion these restaurants express by setting out chairs and tables outside spilling out on to the courtyard, inviting passers-by to sit. Therefore, the following studies will be focused between 12:00 and 14:00 throughout the year since these are the usual lunch hours. When analysing the sky view factor from the middle of the courtyard in Figure 33, we can clearly express the designerâ€™s intention to provide sun at mid-day when we see the solar path throughout the year at hour 13:00. Once this was identified the investigation was followed by testing the sunpath for the spring equinox, and the winter and summer solstice, figures 35 through to 37. The simulations have always been run during the hours 12:00 to 14:00, when the users will most likely use the space.. Page 18
Figure 32: Massing and Carving process
Figure 34: Exploited image of the Piazza showing the restaurants and the transparency of the ground level
Figure 36: Spring Equinox sun path for hours 12:00-14:00 with the point from where the sky view factor for figure 33 was taken
Figure 37: Summer Solstice sun path for hours 12:00-14:00 with the point from where the sky view factor for figure 33 was taken
Figure 38: Sky view factor showing the permeability at the ground floor Pod
Another issue expressed by the lead designer was the need to make the courtyard visually bigger. The architect has expressed the strain of making the program at the ground level of the building as “permeable” as possible. It is because of this design criteria that all the restaurants have to keep an open plan kitchen, or place it in a lower level all together. The nucleous of each area has also been reduced to it’s minimum size, in order to block as little as possible the views to the surrounding streets from the courtyard itself. A second approach towards this same goal was keeping the double glazed windows along the perimeter of the restaurants from floor to ceiling with as few divisions as possible having them reach a height of as much as six meters at the tallest point. Such remark is necessary as the site has a very well mitigated 2 meter slope. This design intention is clearly related to visual comfort and therefore it has been tested with ECOTECT determining the sky view factor from the centre of the courtyard as seen in figure 38. The design team has been fairly successful because the skyview factor from the courtyard,considering the building as a solid volume is 14.5%, but once we take into account all it’s permeability it increases up to 19.5% at the courtyard level. Clearly there are not many views of the sky from the centre of the courtyard, but one feels a lot less density because of this strategy. Page 19
Area of focus AREA OF FOCUS
The area chosen to further investigate is the one outside the restaurants, primarily Cabana and Zizzi. The team decided to focus particularly in this area because although the whole square is equipped for eating outdoors, this is the area that actually receives the sunâ€™s rays while the Jamie Oliver restaurant does not because it is behind the internal northern facade. This solar exposure allows for a lot more possibilities for the occupants, which will be further tested below. In this area we can identify some areas intended for people to spend some time, either seating on the wooden benches or in the restaurant. The area is sheltered from the rain by the canopies that where originally intended for the protection from the downdraft wind, as clearly expressed by the architect. Finally, one can also identify the umbrellas, which are intended for the users who want to shelter themselves from the sunâ€™s rays or to filter the glare.
Figure 39: Plan showing the Area of focus
Figure 40: Image showing the area of focus
SOLAR RADIATION STUDIES
Looking closely at the average temperature at 13:00 throughout the year and overlaying the cloud cover, measured in octas, for the same time period in figure 41, one can assess that it is not only cold but also quite cloudy. The skycover holds the same pattern throughout the year so it is not easy to identify a more cloudy season in comparison to another. However what is observed is that London’s sky is usually either in total, or no cover, having only a few days as partly cloudy, at 13:00.
Figure 41: Temperature and Octas at 13:00 from the Kensington and Chelsea weather station
At a first, glance the available solar radiation for that time period here shown in figure 42 seems to resemble a semi circular shape being stronger in the middle for the summer periods. However on a closer analysis two things are clearly identified. On a first note, there is more direct radiation on the second half of the year, adding for a higher global radiation that falls abruptly in October. The second thing the team identified is the amount of direct solar radiation available in March, which is higher even than that of April.
Figure 42: Available direct and diffused solar radiation at 13:00 from the Kensington and Chelsea weather station
Figure 43: Incident direct and diffused solar radiation at 13:00 on the area of focus
After studying the available global radiation the only logical step that followed was to analyse the incident in the area of focus, again, always at 13:00. Figure 43 shows that the direct and diffused radiations are quite similar for the first and last quarter of the year while during the summer months the direct solar radiation dramatically increases. This direct solar radiation can only be used as a comparison to see how much of it falls in our area in regards to the available radiation, because it is not entirely accurate for any given point. This is because it is averaged throughout the whole surface at the specific hour, and given the area of such surface, it is bound to be overshadowed by the building on some parts at any specific moment, resulting in a decline in the average. The diffused however, being a result of the bounces and reflections in the interior of the courtyard is significantly decreased from that of the available to an average of about 50 W/m² for the better part of the year, and this one, is accurate for any given point in the surface.
Finally, adding together the available direct solar radiation with the incident diffused, will result in the actual global radiation an occupier receives when standing in the sunny patches of the area and at the time of our study. We can see that even in winter the direct solar radiation is very high in comparison to the diffused radiation. Figure 44 clarifies that the global radiation falling on a shaded area will be of only 15 W/m² while in the sun it will be that of 115 W/m² during the month of January that lies in winter.
Figure 44: Incident diffused solar radiation (figure 43) + available direct solar radiation (figure 42)
COURTYARD - WIND STUDIES
When analysing the wind, the team focused mainly on the frequency of the wind patterns as a reference to identify where to run the simulations from. Figure 45 depicts the frequency and intensity of wind patterns for the four seasons obtained from the weather file using Weather Tool. Again, due to the clear interest of exploiting the courtyardâ€™s potential at lunch time, the focus of the investigation was at mid-day. As a general guideline, during this specific time, at the winter and summer solstice the wind tends to blow from the west mainly. While in the spring it becomes more often to the south-west and finally in autumn it blows from the south-west or the south direction completely. Hence these are clearly the predominant wind directions. Wind for the winter is particularly difficult, at least at this hour, because it literally comes from everywhere with a slight predominance from the south west, and at very high speeds, but it is clearly not a main concern for this research, mainly because of two singular reasons. For one, it is clear that the predominant wind blows from the south west, or maybe even west. On a second note, as previously seen, the winter temperatures for London are already quite low, suggesting that using outdoor spaces for this season, might be something extremely hard to accomplish. Because the aim of the research is to establish if the courtyard has a potential of being used during lunch hours, the team has concluded that there is not much benefit in proving that one is very well protected from the wind when the temperature is only 5Â°C. Although conditions will be significantly better, it would be very ambitious to want to achieve comfortable scenarios for having lunch outdoors during winter, nevertheless, it is not unachievable. For the purpose of studying the courtyardâ€™s potential at mid-day the team will run simulations using computer fluid dynamics using WinAir and Ecotect for the three most predominant winds (south, south-west and west) to study their effect in the courtyard.
Figure 45: Wind roses showing frequency of wind direction and intensity through the seasons at mid-day
COURTYARD - WIND SIMULATIONS Figure 46 illustrates the west wind which shows little or no penetration into the square. The highest speeds are observed at the southeast and the northwest entrances. Strangely enough the speeds resemble each other though they are completely different. The southeast entrance is significantly smaller and the building crosses directly above it, while the northwest entrance divides the building completely. This is clearly due to the bounces and pressure fields generated along the urban context. This is the most frequent wind in summer, so the fact that there is a small penetration or even a small area that does have more turbulence than another could be desirable and even more of an advantage than a disadvantage.
Figure 46: Computer fluid dynamics simulation showing turbulence generated in the piazza by the west wind
Looking particularly into our area of focus we see that the wind does not really affect the inner courtyard, and therefore we can state that the courtyard is protected from the west wind.
When the wind blows from the southwest we can clearly see the turbulence forming in all of the entrances to the courtyard, especially towards the northwest entrance where the wind speed is higher even than with wind from the west. Now the other three entrances suffer higher wind speeds and this is clearly seen towards the northeastern entrance. This is clearly due to this areaâ€™s tube like form which is channelling and therefore concentrating the wind. The southwest wind would clearly be the most dangerous one because it is the most frequent one throughout the four seasons. Nevertheless, it does not really generate a turbulence inside the courtyard. It can determined that it could generate a higher turbulence on the west side of our area of focus, but again, only on a small area. Figure 47: Computer fluid dynamics simulation showing turbulence generated in the piazza by the southwest wind
Figure 48: Computer fluid dynamics simulation showing turbulence generated in the piazza by the south wind
South wind is a completely different case because it is when the courtyard is even more protected. The fact that the entrances are not located towards the corners of the building is really the reason why the courtyard is so well protected. The urban tissue has clearly diverted the wind from the entrances concentrating it on the surrounding streets, so although wind speeds are higher in the surrounding, it is safe to state that the courtyard is clearly well protected from this wind as well.
After learning from the architect in charge of the design at RPBW that the canopiesâ€™ main purpose was to protect the courtyard from the downdraft wind, the team felt the need to test this using computer fluid dynamics. Effectively in this section in figure 49 the wind is diverted, this is not only because of the canopies, but also because of the relatively small distance between internal facades, which is almost 20 meters across. These strategies are clearly very effective towards making the courtyard less windy.
Figure 49: Computer fluid dynamics simulation showing turbulence generated in the piazza by downdraft wind
When the spot measurements were taken, wind was one of the hardest parameters to determine, because during a single reading one could get very different values due to high speed drafts. Because wind is such a hard thing to measure accurately due to the fact that it constantly changes direction and intensity altogether, an average was obtained as an attempt to unweave patterns, and determine windy areas, or at very least, windier areas with respect to other.
Figure 50: Wind spot measurements taken on the first field studies
We can see that these measurements somewhat resemble the south west wind, having a higher turbulence to the north entrances. This is clearly because as we have previously established, this is the most common wind direction. This proves that the computer fluid dynamics model is quite accurate. This also proves the conclusion that the courtyard is fairly sheltered.
Having established that the courtyard is very well protected from the most frequent winds and the downdraft wind, wind speeds, for further studies and simulations will be assumed constant at 0.5 m/s. This liberty combined with the conditions provided by the Kensington weather station and the incident solar radiation of figure 43 which have been studied before are all combined to estimate the Physiological Estimated Temperature (P.E.T.) at 13:00 hours in the area of focus. The last thing needed for the P.E.T. is the occupant, which will have a different clothe value according to the season, as seen in the yearly P.E.T. figure 51. The rest of the parameters have been set as follows: • • • • •
Male thirty years of age weighing 75 kg 175 cm. tall activity rate of 120 W (sitting down eating, high metabolic rate)
The P.E.T. is being displayed along with De Dear’s equation for a comfort band for 90% and 80% acceptability. A predominantly cold sensation has been predicted due particularly to London’s climate, so the fact that the courtyard is protected and therefore wind speeds are low is something very desirable. This graph should be used as a reference as to determine the potential in each day to use the courtyard for lunch. The fact that in April, May or September the P.E.T. is significantly out of the 80% acceptability does not necessarily mean that it will be uncomfortable to use. Each peak could be further studied in order to shorten the distance between it and the comfort band established. In some cases a cold spike of the P.E.T. can be nullified by just moving to a sunny area. As an example, two peaks are being closely studied. The first case to be studied will be a cold peak, March 25th. The air temperature is already 2.5°K below the 80% acceptability for the comfort band calculated. Moving into a sunny area, which as shown, given a clear sky there will always be one at midday, the difference is not only suppressed, but with a 4 C increase, the new P.E.T. value is in the calculated comfort band. One can increment the sensation even further by increasing the metabolic rate with a hot drink or meal. Page 28
1.2 March 25th Base Case Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
First Iteration : 14.5°C : 4/8 : 46% : 84 W/m² : 0.5 m/s
P.E.T : 13.8°C
Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
Second Iteration : 14.5°C : 4/8 : 46% : 257.7 W/m² : 0.5 m/s
P.E.T : 17.8°C
Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
: 14.5°C : 4/8 : 46% : 257.7 W/m² : 0.5 m/s
P.E.T : 19.5°C 10% P.E.T. increase through metabolic heat provided by hot beverage
Figure 51: Calculated yearly PET for 13:00 using the parameters for the weather station for the case stated in the text
Base Case Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
First Iteration : 27.5°C : 8/8 : 50% : 173 W/m² : 0.5 m/s
P.E.T : 31.0°C
Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
Second Iteration : 27.5°C : 0/8 : 50% : 54 W/m² : 0.5 m/s
P.E.T : 27.6°C
Temperature Cloud Cover Relative Humidity Global Radiation Wind Speed
: 27.5°C : 0/8 : 50% : 54 W/m² : 1 m/s
P.E.T : 26.9°C
For analysing a hot peak, a closer study is done for the one in July 21st. Looking at the conditions that set the P.E.T. it is clear that the fact that the octas is eight is a determining parameter. The wind had already been established as fixed at 0.5 m/s, so now one of the only variables left for adaptive comfort would be moving from sunny areas to areas under the shade. On a fully covered day, there is not too much of a difference between one and the other. Because the purpose of this investigation is to determine the potential for using the courtyard to have lunch on a given good day, the octas have been removed, in order to examine this potential in the summer. Removing the octas now reveals a pronounced contrast between overshaded and sunny areas, and by moving into a shaded area, as shown in the second iteration, a P.E.T. reduction of almost 3.5 K is achieved, which would be in the verge of the 80% acceptability. In the third iteration, it was assumed that the subject moved into an area which is slightly more turbulent, as we have seen before in wind simulations. These areas, closer to the north-west corner, are also shaded, and the P.E.T. for the base subject would be again, in the calculated comfort zone. Page 29
Potentially good days for having lunch in the courtyard
ADAPTIVE COMFORT Finally, after the previous studies, a final yearly P.E.T. has been plotted. For this calculation, octas has also been set fixed at 0, meaning completely clear skies throughout the whole year for London. The other premise set for the calculation was that the subject for whom the P.E.T. is calculated is always in the sun. It has already been proved that on any given day there is always going to be a sunny patch in the area of focus. Therefore, these two factors combined together made up for simulating with the highest possible solar radiation on site. In the previous P.E.T. study, it has been shown how hot peaks such as the ones being shown here, in figure 52, can be mitigated by just moving from a sunny area into a shaded one, achieving a P.E.T. value in the comfort zone. The high peaks can therefore be disregarded, and it can also be stated that is as high as the low peaks will go before adding more to oneâ€™s Clo value or metabolic rate. This is the case, because as stated before, the maximum global solar radiation levels are being calculated for this scenario.
Figure 52: Calculated yearly PET for 13:00 using the parameters for the weather station for the case stated in the text with no octas
Hot peaks can be mitigated as shown in figure 51
Conclusively, what the figure is showing then, is the possibility of using the courtyard at lunch hours throughout the year on a given day with clear conditions. It is ultimately showing the extent of the adaptive comfort possibilities that the courtyard is offering by having shaded and sunny areas, as well as areas with more wind in comparison to others which have significantly less. It can be therefore stated that the courtyard is a relatively successful place, as it provides out door comfort for three fourths of the year to the occupants for which it was intended.
INDOOR STUDIES - APARTMENTS
Legend 70 - 75 dB 65 - 70 dB 60 - 65 dB 55 - 60 dB
RESIDENTIAL BLOCK - CONTEXT AND LOCATION The residential building was included in this mixed use development as a requirement from the Camden Council. Another condition imposed, was that the building should house a certain percentage of affordable apartments. This action creates greater incentives for people to live in central urban areas, which from an environmental and sustainable point of view is desirable, since this is an efficient measure to avoid the spreading of the city and the growth of suburbs. Hence, the city becomes more compact and still grows, using the existing transportation infrastructure and reducing the displacement of people, which can be understood as one of the main causes of Co2 emission nowadays, as transportation is the third highest source of emissions worldwide. It is important to highlight that there are only 10 car parking spaces available for the entire building (109 apartments). These are available for a small number of the private apartments. Consequently the remaining residents are encouraged to use public transportation, walk or cycle. The Housing block is located in the corner of two main streets: St Giles High Street and Earnshaw St. According to the design statement, the position of the apartments is related to the existing residential uses in the Centre Point Tower Podium and the area around the St Giles-in-the-Fields Church Gardens. In order to find the appropriate balance between the building volume on the site and the existing buildings around it, the architects also chose this location for the apartments so that the lowest part of the complex would turn to the Church. The main streets around the complex are characterized by heavy traffic during day time. Sound spot measurements that were taken show the amount of noise pollution being generated ( figure 53). It can be seen that the courtyard creates an area that is more protected, with lower levels of noise. By contrast the highest levels were measured along St Giles High Street and Earnshaw St, varying between 61 and 75db. Researches undertaken by the World Health Organization (Berglund 1999), recommended that the sound pressure level on balconies, terraces and outdoor living areas should not exceed 55 db during the daytime. In addition the same study confirmed that long-term exposure to levels higher than 65 db due to road traffic could result in some damage to human health. Therefore the location of the apartments in relation to the site is problematic and this is particularly relevant in the context of natural ventilation and the need to open windows for cooling. Figure 54 shows the traffic of central St. Giles high street on a regular week day. Page 31
Figure 53: Spot measurements for sound levels measured in dB at the respective points chosen during the field studies.
Figure 54: St. Giles high street traffic during a weekday Affordable Apartments Private Apartments
The residential building is a separate block which comprises two types of dwellings (private and affordable) as seen in the figure 56. The two types are completely separated from each other with separated entrances and lobby areas.
South Apartment 14 13 12 11 10 9 8 7
The entrance of the affordable apartments faces Earnshaw St, while the private apartments are accessed through the courtyard. From an energy and environmental perspective, the main difference between the two types of dwellings is the cooling and heating systems adopted. The Affordable apartments are naturally ventilated with a heat recovery system which provides pre heated air for the occupants for winter times, by contrast the private apartments are air conditioned. This has an adverse effect on the energy consumption and is seen by the team as an unnecessary measure in the context of this climate.
6 5 4 3
Figure 55: Apartment Block of Central St. Giles with studied apartmentâ€™s location
Figure 56: East Elevation of the apartment block showing private and affordable
The fact that the affordable housing is the only naturally ventilated part of the entire mixed use complex, drew the teamâ€™s attention. In addition, in the same building block, dwelling units which are conditioned by artificial means, raised a question regarding the necessity of applying this kind of solution in the climate of London. Those issues were the starting point for investigating the environmental performance of the building. The study focuses on two apartments, a private apartment and an affordable one facing north and south respectively as shown in the figure 55. The design of the facade in regards to the flats orientations was also an issue explored by the group. Page 32
5.5 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5
N Affordable Apartments Hall
Private Apartments Hall
Figure 57: Spot measurements for wind from the south west showing the impact on both of the apartment entrances
ACCESS TO THE APARTMENTS AND TRANSITIONAL SPACES Londonâ€™s prevailing winds are from west and south west as shown in the windrose (figure 59). Spot measurements of air velocity were taken around Central St Giles in a specific day when according to Weather Underground the direction was from south west (figure 57). The urban morphology which defines Earnshaw street increases the winds right next to the affordable housing entrance and lobby, creating uncomfortable conditions most of the year, This was confirmed in interviews of the residents. These circumstances were also experienced by the team while conducting field studies in October. The entrance area and lobby were found to be a particularly uncomfortable place to stay in for more than a short time when while conducting interviews residents were not willing to stay in the same place for more than a few minutes. The glass door of the lobby being broken three times in the ten months prior to the field studies, broken at the time of the measurements as shown in figure 58, is yet another indication for these conditions. Page 33
Figure 58: Picture showing broken door in the south west entrance
Figure 59: Windrose showing Londonâ€™s yearly wind speeds and frequency
26.5 (C) 24.5 (C) 22.5 (C) 20.5 (C) 18.5 (C) 16.5 (C)
From the temperature spot measurements that were taken along the path in which a resident travels every day from the street to inside the apartments, it is possible to see that a gradual change of thermal conditions from the outside in and vice versa is not happening (Figure 60). It can be seen that even in the season the spot measurements where taken, which is not the coldest of the year, the contrast of temperatures is high; 10 K with outside temperature of 16 C and 26 C in the corridor. In the field surveys that were conducted, residents reported feeling uncomfortably warm in the common areas. These conditions reduce the potentiality of the common areas to contribute to the comfort conditions in the apartments, as they do not provide an opportunity to adjust gradually to the indoor and outdoor conditions, working therefore as a ineffective transition zone. To summarise, in regards to the apartmentsâ€™ block location and its relation with the urban context, the team concluded that it could be considered being placed in a different area of the site, facing quieter streets and using better the protected zone of the courtyard. This way unpleasant noise from the pubs during the night and from the motor vehicles during day time could be reduced. The Affordable housing entrance position would also be improved if accessed from a less windy area similarly to the private apartments lobby which is accessed from the courtyard. This could also contribute to the use of the square by the residents. Some of the from the residents from north apartment block that were interviewed reported that it would be nice to enter from the square.
Figure 60: Section through apartment block
N THE APARTMENTS BLOCK FEATURES Apartments type and size: The apartment building comprises of 109 apartments of which 53 are affordable and 56 are private. These include: studios, one and two bedroom apartments sized from 32 Sq m to 88.2 Sq m respectively, as shown in a typical floor plan in figure 61. The apartment’s floor to floor height is 2.88 m, as seen in figure 62.
Private Apartments Studio 1 bed 2 bed
Materials and construction:
With the intention of minimizing the effects of solar radiation, a low emissivity glass with 1.4 U value was used. A heavy weight glass was used in the facades facing west and south in order to meet the acoustic requirements for the residential buildings The windows used can be seen in figure 63. The wall construction is a unitised system with external terracotta rainscreen panels, air cavity, insulation and an internal finish of plaster boards as seen in figure 64. According to the engineer, the glazed ceramic is a very durable and resistant material which requires low maintenance.
Affordable Apartments 1 bed 2 bed
Figure 61: Typical floor plan of the residential building Source: After Renzo Piano Building Workshop Terracotta cladding system Insulation 0.58 m
As mentioned by the project engineer from ARUP, the facade is key to a building’s performance and one of the elements that could not be changed easily throughout the life of the building. Therefore it is critical to achieve a high performance of the façade in terms of daylight provision in relation to the building use, thermal performance, whilst at the same time being attractive. High specification of materials and details were used in the façade and design standards resulting in a considerably higher performance than required by 2006 regulations.
A heat recovery system, extracts air from the bathroom and kitchen and supply the bedroom and living room with preheated air.
The specific type of air conditioning installed in the private flats is not known to ARUP since the developers were in charge of designing the systems of this particular part of the complex. However the team acquired some information through interviews with residents and real estate agents. The main observations are that each room had its own thermostat and the air conditioning units inside the flats are used both for heating and cooling. Therefore the apartments have no radiators and there is an under floor heating system in the bathroom. Page 35
Figure 63: Low-e double glass used in the project Source: schueco.com 0.4 m
Each apartment has its own water reservoir. The main reason for choosing this method is to allow for a smaller sized distribution system.
The affordable apartments have radiators in all the rooms, apart from the bathroom and the hall. One thermostat is provided for the entire flat. This according to residents generates some difficulty in choosing the temperature to be set, since the living room and bedroom often have highly different conditions.
The heating system has a centralised high efficient boiler located in the basement which is connected to the apartments through pipes that go up within the corridor shafts.
Figure 62: View and section of the apartment block Source: After Renzo Piano Building Workshop
Figure 64: West elevation Source: After Renzo Piano Building Workshop
Figure 66: The courtyard facades
Window size and design: From the interview with the project architect from Renzo Pianoâ€™s Building Workshop the team learned that punch hole windows for the design of the faĂ§ade was chosen in order to minimise the amount of glass in the offices. The depth of the windows and the layering of the terracotta faĂ§ade were created in order to allow for some shading for the windows as well as establishing a relation with the traditional brick facade design of the neighbouring buildings. For the residential block the same facade design was used, but adjusted to the lower floor to ceiling height (2.9 m in the offices and 2.4m in the apartments). It is important to highlight that generally the dimensions of the windows are the same along the different orientations of the apartments block as seen in the figures 66, 67 and 68 . The size of the windows is increased in the balcony areas and in the glazed areas that were created in order to fragment the mass of the building. Figure 65: Facade details Source: Renzo Piano Building Workshop
Figure 67: Facade to the west elevation
Figure 68: Facade to the north elevation
Figure 69: Image inside the apartments
Figure 70: Image inside the apartments
APARTMENTS GENERAL INFORMATION AND RESIDENTS INTERVIEWS The affordable apartment where the team focused its research on has a floor area of 48 m². It is located on the 12th floor of the apartment block and it is a one bedroom apartment, as shown in the Figure 71. The flat is inhabited by one resident, Azeem Ahmad ,a 40 year old male who is living in this building since December 2010.
Another resident that was interviewed was Lara. Her apartment faces west and has a smaller area in comparison to Azeem’s apartment. She mentioned that during the summer she can’t use the internal blinds to avoid direct solar radiation while the windows are open as they open inwards. In addition she expressed dissatisfaction with the size of the windows and found them difficult to operate due to their weight. Specifically, she said that the 40 cm height of the sill reduces the possibility of having a table or any furniture close to the windows. In her flat, two of the windows cannot be opened due to the furniture location. Carmel Burke’s apartment also faces west and includes a balcony. When interviewed she reported that most of the year she leaves the balcony door opened for ventilation and cooling. When the windows are opened she goes as far as using ear plugs to avoid external noise. Page 37
The resident in general is satisfied with his apartment and he reported that the views of London from there are impressive, as seen in Figure 70. Another positive aspect according to Azzem is that the apartment’s energy consumption and heating expenses are low and he reported at the time of the survey in October that he didn’t turn the heating on since February 2011. The resident also enjoys living at this location since he is able to go to work by bicycle. Nevertheless during the summer when the windows need to be opened in order to provide acceptable levels of comfort, he finds the noise generated by motor vehicles and pubs disturbing, especially during night time.
Figure 71: Floor plan of the north apartment
Figure 72: Image inside the apartments
Figure 73: Image inside the apartments
Figure 74: Image inside the apartments
The private apartment which the team was able to access is located on the first floor of the building. It is a one bedroom apartment with a 56 mÂ˛ overall floor area. Its facades are facing St. Giles High Street and Earnshaw street. A winter garden is one of the particular features of the flat. It is a balcony enclosed with operable glass louvres to the street side that provides protection from the wind. The flat is currently inhabited by a 20 year old student who had been living there for only one month prior to the date of the field study in mid-October. When interviewed he expressed satisfaction with the location of the apartment which allows him to walk to his university every day.
Figure 75: Floor plan for the south apartment
The windows in the apartment are Tilt &Turn of the same size and type as the rest of the building block. However the occupant reported that they are locked and he didnâ€™t receive the keys from his land lord. Therefore currently the only openable window in his apartment is the balcony door, which is almost permanently closed due to the high noise levels. As a consequence, when he feels uncomfortable with the internal temperatures he uses the air conditioning. Page 38
5 21 X LU
0 25 X LU
FIELD WORK As part of the field studies, temperature and lux spot measurements were taken inside both apartments at different days. North Apartment In the affordable flat facing north, a temperature variation of almost 4°C can be observed as shown in figure 74. The warmest areas are the Bathroom and the Hall which have no windows or external walls thus heat loss is kept at a minimum. In addition it is likely that the high temperatures of approximately 26°C in the building corridor contribute to the heating of the apartment’s hall since these two areas are only separated by a door. According to the project engineer the heating pipes inside the corridor shafts in combination with lighting heat gains and the high level of airtightness are the main reasons for the overheating of the corridor. He also mentioned that with the current building regulations which require a very good level of air tightness they find that this problem is being reported in a few other of their recent projects and that ventilation may need to be introduced in this kind of enclosed spaces. The lowest temperatures were found in the living room and kitchen because the resident had opened the windows just before the spot measurements started. The external temperature at the time of measurement was 17.5°C with clear sky conditions. As seen in the figure 73, the highest lux levels can be observed in the bedroom which is the room with the highest window to floor ratio (84%). The illuminance levels were observed to be satisfactory in the kitchen, however they were significantly lower when compared to the bedroom. This fact drew the team’s attention and raised another question regarding the necessity of having such an amount of natural light in the bedroom, as a reference the British Standard for 8206 recommends lower illuminance levels for those areas and higher levels for kitchens. Moreover the dweller of the flat complained about the glare in the morning when he is sleeping, because it is not possible to be completely contained with the existent blinds. Page 39
Figure 73: Floor plan showing the Lux levels in the north apartment October 28th, 14:00 External air Temperature 15.0 ̊C
70 24. 70
Figure 74: Floor plan showing the temperature spot measurements in the north apartment
Figure 75: Floor plan showing the Lux levels in the south apartment
October 25th, 12:00 External air Temperature 15.7 ̊C
South Apartment At the time of the spot measurements in the private flat, the air conditioning system was not operating. The external temperature was 15.7 ̊C and the sky conditions were heavy clouds. A temperature difference of up to 1.6 ̊K was measured within the apartment as seen in figure 76. The warmest area was the apartment hall which is entirely surrounded by rooms. Unlike the north apartment, higher temperatures in the bedroom in comparison to the living room were found. The lowest values were measured in the winter garden which is an external space protected by glass louvres. The overall temperature in the south apartment, is slightly lower when compared to the north. This fact didn’t follow the team’s expectation since both apartments have similar envelope properties and the south flat receives direct solar radiation. A reasonable explanation for the lower temperatures could be that the south apartment is located in the first floor of the building just above a restaurant which at the time of the measurement was unoccupied. The restaurant has a double height space which is fully glazed incurring significant heat loss. It is likely that the difference of temperature between this two attached spaces is increasing the heat loss through the apartment’s floor. Other reasons could be that the south apartment has an obstruction angle of XX or the cloudy sky conditions. Lux measurements shown in figure 75 reveal that the brightest area is the living room, especially around the winter garden where a large amount of glass can be found. The kitchen is located in the deepest area of the room, however due to the size of the windows, satisfactory illuminance levels are achieved.
Figure 76: Floor plan showing the temperature spot measurements in the north apartment
Apartments Dataloggers Measurement 21-25 Oct
Azeem Livingroom DryBulb (C) Azeem Livingroom DryBulb (C)
Azeem Bedroom DryBulb (C) 20.00
External Temp (C) Global Horizontal Radiation (W/m )
Comfort Zone 400
DATA LOGGERS MEASUREMENTS AND MEAN INDOOR TEMPERATURE CALCULATIONS
The data Loggers were placed in both apartments the same week, from the 21st to the 25th of October. The measurements were plotted against the comfort band deducted for the month of October based on De Dearâ€™s Equation.
0 Fri Oct 21
In the north flat, one data logger was positioned in the living room and the other in the bedroom. Figure 77 shows that the temperature within the rooms is quite stable; however there is a difference of almost 2 K from one room to the other. The living room mean temperature during those days was 25 C and was slightly above the comfort zone, while in the bedroom it was around 23 C, which is still within it. This difference was confirmed with the Mean Indoor Temperature (MIT) Calculations, where the living room presented higher temperatures due to internal heat gains generated by the kitchen appliances and to its smaller window to floor ratio in comparison to the bedroom. In three instances when the windows were opened, an abrupt indoor temperature drop occurred. This gives good indication of how much the flat is sensible to an increase in the air change per hour rate. The MIT calculations also show that the average temperature in the living room rises 12 C above the outdoor temperature. A reasonable explanation for such high temperatures, is that the building has a high level of airtightness, also the fresh air requirements are provided by a heat recovery system that keeps it at room temperature.
Sat Oct 22
Sun Oct 23
Mon Oct 24
Tue Oct 25
Figure 77: North apartment data loggers
In the private apartment the data logger was placed in the living room. During these days, the resident reported that he was at home only early in the morning and late in the afternoon, so he didnâ€™t turn the air conditioning on. As seen in the Fig 78, some peaks in the internal temperature can be seen when there is an increase in the global radiation. Those peaks occur during the hours in which that living room receives direct solar radiation. MIT calculations proved the assumption that some heat loss is happening through the floor of the flat. In the current scenario, the average temperature in the living room rises 11C above outdoor. Considering the fact that the restaurant below the apartment will be occupied within the next months and the temperature inside it will be thermally controlled during the entire day (as in Zizzi restaurant), new MIT calculations without considering the heat loss through the floor was done. This case revealed, an average temperature rise above outdoor of 14K. This gave the team an indication that the south apartment is going to overheat significantly in summer. Page 41
15.00 400 10.00 200
0.00 Fri Oct 21
Sat Oct 22
Figure 78: South apartment data loggers
Sun Oct 23
Mon Oct 24
Tue Oct 25
Figure 78: Position of the data loggers within the building
Energy Index. KW/h per m² dwelling floor area
Current Scenario overall Window to floor ratio: North Apartment: 41,70 % South Apartment: 43,50 %
Figure 79: Heat loss rate (building envelope and ventilation) W/K per m² dwelling floor area. Source: After Yannas 1994
Energy Index. KW/h per m² dwelling floor area
Figure 80: Heat loss rate (building envelope and ventilation) W/K per m² dwelling floor area. Source: After Yannas 1994
The Energy Index Calculation Worksheet (Yannas, 1994), was used in order to have an overview regarding the energy performance of the apartments. As seen in the fig 79, both apartments have a heat loss coefficient below 1 W/K per m². The energy required for space heating is also quite low when compared to Passive Haus’ benchmark (15kWh/m²). For these calculations the space below the south apartment was considered occupied as this will be the case in the coming months. The result shows that the north apartment’s annual space heating required is almost two times higher in comparison with the south apartment. Improved Scenario overall Window to floor ratio: North Apartment: 15 % South Apartment: 25 %
During the field studies the team realized that there were some possibilities to increase even more the performance of the apartments by reducing the size and amount of windows, which would also reduce the heat loss coefficient. This was also backed by the lux spot measurements explained before. A further improvement of the building performance was considered by the team to be an important investigation. Particularly in the context of new building regulations and standards like 2016 code for sustainable homes’ requirement of 100% reduction in carbon emissions in the private sector (communities and local government, 2010). Based on the recommendations from Yannas (1994), the team ran the calculations again, considering a window to floor ratio of 25% for the south apartment and 15% for the north apartment. The result achieved was a reduction of 66% in the energy index for the north flat and 42.87% in the south. An interesting outcome was that using these different ratios according to the orientation, the energy index for both flats reached the same values. Page 42
ANALYTIC WORK - NORTH APARTMENT - SUNPATH STUDIES Following the results of the manual calculation and the premise that reducing the amount of windows would result in a significant reduction in the energy consumption the team proceeded to investigate the implications of this change. First the sunpath in relation to the apartment was studied using an Ecotect simulation as shown in figure 81. The purpose of this run was to understand the accurate exposure of the indoor space and to identify potential problems and opportunities.
From this study It can be seen that the north apartment receives very little direct sun due to its orientation and the obstruction of the other buildings throughout the year. During the autumn and spring direct sun enters the apartment only in the early morning. In the summer the apartment receives direct sun from early to late morning and late in the afternoon. In winter, however, the apartment receives no direct sun at all, therefore, at times when direct radiation is most desirable (in the winter), the apartment does not receive any. Most of the direct solar radiation is received in the summer when it is not desirable (as indicated by MIT calculations shown previously, the apartment overheats in the summer despite its north orientation. Furthermore due to the full height window in the bedroom facing northwest a lot of the direct sun is received in the bedroom in an early hour which could be disturbing. It can be concluded that the specific arrangement of the windows and their size does not contribute in terms of desirable heat gains in the winter and that allocation of the windows in relation to the function is not ideal. The large glazed area in the bedroom is not beneficial and could even be disturbing, in fact, during the winter the large amount of glazing will contribute to heat loss. Dec 9:00 Page 43
Figure 81: Ecotect Sun path simulation for the residential block
Figure 82: Sun trajectory with respect to the building showing the north apartment
Figure 83: Sun path affecting the north apartment calculated with Ecotect
6.6 6.6 4.6 2.6
16.6 10.8 4.6
6.6 10.8 2.6
0.6 4.6 6.6 10.8
2.6 0.6 4.6 2.6 ANALYTIC WORK NORTH APARTMENTS - DAYLIGHT STUDIES Based on the conclusions from the sunpath simulation the team proceeded to check the implications of a reduction in size of the windows on the daylight levels in the apartment. For this purpose a Radiance model simulation was conducted. First the model was compared and calibrated as per the spot measurements of figure 73 on page39. Once the model was calibrated the existing daylight levels were evaluated in comparison with CIBSE guidelines. A simulation was run with the worse case scenario of overcast sky conditions, and the daylight factor was checked throughout the apartment. As a result one can conclude that if a satisfactory daylight level is achieved in these conditions it gives a good indication that good daylight levels are provided. CIBSE guidelines indicate a daylight factor of 2% as a good level of daylight. It can be seen in figure 84 that in the existing situation the daylight levels are significantly higher than 2% next to the windows in the living room and in a large area of the bedroom. However, the distribution of light is not even, with big contrasts of up to 20% in a small room 4m deep. This poor light distribution adversely affects the perception of light conditions. A darker part of a room with a large contrast of light levels would be perceived as too dark even though its level could be satisfactory in other conditions. As a result people would be inclined to use artificial light when it could be avoided. Therefore the team concluded that the apartment could benefit from a reduction in window size in terms of daylight levels.
Figure 84: Daylight factor simulation for the current situation
Window/Floor ratio: Livingroom: 48% Bedroom: 84% Overall Apartment:
Table 1: Current window/floor ratios
Livingroom elevation Figure 85: Current apartment facade scheme Page 45
10.0 7.15 10.0 7.15
5.25 3.35 3.35
2.40 1.45 3.35
7.15 2.40 3.35 5.25
10.0 0.50 7.15 2.40
Figure 86: Daylight factor simulation for the proposed scenario
Window/Floor ratio: 28% Livingroom: Bedroom: 28% Overall Apartment: 19.5%
Table 2 shows the proposed ratios: - The living room ratio was reduced from 48% to 28%. - The bedroom ratio was reduced from 84% to 42% - The overall apartment ratio was reduced from 42% to 19% . Fig 86 is showing the daylight factor achieved in this scenario.
Table 2: Proposed window/floor ratios
Livingroom elevation Figure 87: Proposed scenario facade scheme
A series of simulations were conducted with different window sizes. Finally, the proposed option shown in figure 87 included raising the sill of all the windows to 800mm and blocking the full size windows in the living room and in the bedroom. The reasons these options were taken are: Below 800mm the window has a minor contribution to the daylight level. Furthermore from the field studies it was observed that windows with sills below this level are more restrictive in terms of optional internal layouts and furniture position. The full glazed window in the bedroom was found not useful in terms of solar radiation and even created disturbance with early morning direct sun and the full height window in the living room is in close proximity to the corner windows thus was not predicted to contribute much to light levels. As it is not an openable window this change will not affect ventilation.
It can be seen that a good daylight factor of 3% is achieved in 80-90% of the room both in the bedroom and the living room. It can also be seen that a better distribution of light is achieved with a significantly smaller contrast within the room (a range of 0-10%, in comparison to a range of 0-20% and 0-15%in the base case). Page 46
TAS Thermal Simulation Model. Colours are indicating the different zones.
ANALYTIC WORK - NORTH APARTMENT THERMAL SIMULATIONS Once it was established that the reduction of window size does not have an adverse effect the team proceeded to investigate further the thermal performance of the apartment. Using the MIT and Energy Index manual calculations as guidance a TAS simulation was conducted in order to assess the change in indoor temperature over time. The research question that was raised at the starting point of this investigation focused on the implications the window reductions implied. - How does the size of the windows affect the energy performance of the apartments? A TAS model was created. As shown in figure 88. The different rooms in the apartment were defined as different zones to allow the team to assess them separately and define different internal conditions. The adjacent apartments at the same floor as well as above and below the apartment were assumed to have the same conditions as the apartment that was investigated and therefore were not zoned. The building corridor and stairwell were assigned each a separate zone as the field studies indicated that the corridor had significant internal gains resulting in a higher temperature than that of the apartment. The staircase had different conditions to both the apartment and the corridor, with less internal gains and an external wall. The inputs of the model were based on: - The field studies - Interview with RPBW Project Architect - Interview with ARUP Project Architect - Assessments that were made using the MIT and Energy Index calculations - The Building Regulations, - Standards and relevant literature.
Figure 88: TAS thermal simulation model with colours indicating the different zones
Infiltration: Ventilation: Appliances: Computer: Microwave: Fridge: Toaster: Kettle: Stove:
0.2 ac/h 24h 0.0 ac/h (when heat recovery is operating) 0.13 ac/h during occupancy times (when heat recovery is not operating)
Materials: Windows: Glass: Double Glazing U Value : 1.53 W/m² Frames U value 2.2 W/m²
300 w 1300w 50w 700w 1800w 1150w
U Value: 0.23 External Walls: Glazed Terracotta: Insulation :Polyurethane expanded Thickness: 90mm Division Walls : U value: 2.23 Solid Wall. Layers: Concrete, PUR 50mm and Plasterboard Lighting 2 x 20 w lights in the livingroom and bedroom
Table 3: Thermal Simulations Inputs (Base Case)
The model was then compared and calibrated with the Data loggers measurements that were taken on October. Figure 90 shows a comparison between the air temperature in the bedroom as measured with the data loggers, and the resultant from the TAS simulation for the same time. The same weather conditions as the data loggers week were used (based on data from ‘London grid for Learning’ website for Westminster Weather Station for those days). It can be seen that the simulation temperature level is similar to the data loggers measurement. The abrupt in room temperature seen in the data loggers graph are a result of window openings. As part of the calibration process the model inputs were adjusted further and the final inputs that were used are presented in tables 3 and 4. As the apartment has a heat recovery system it was assumed that when the indoor temperature is at or below comfort level and external temperature is below comfort level the heat recovery system would start operating providing fresh air at room temperature thus no additional ventilation is taken into account apart of infiltration at these times. During the data loggers week it was observed and confirmed with measurements that the heat recovery system was operating and therefore providing air at room temperature. Page 47
180 minutes/day 10 minutes/day 24 hours 5 minutes/day 10 minutes/day 25 minutes/day
Table 4: Required ventilation fresh air
Figure 89: Yearly mean Temperatures with plotted comfort band for the months focused
In order to have an overall indication of the performance of the apartment throughout the year the climate of this location was investigated and typical weeks for the summer and winter were identified as shown in figure 89. 4-10 January was selected as a typical week of the coldest month with an average temperature of 6 C. 9-15 Aug was selected as a typical week of the warmest month with an average temperature of 18.9 C. W/m ²
Fri Oct 21
Sat Oct 22
Sun Oct 23
Mon Oct 24
A thermal comfort zone for each week was determined using De Dear’s equation in order to represent the desirable conditions in the apartment as shown in figure 89.
Figure 90: Data loggers and TAS calibration Page 48
Winter week Once the initial research questions were established in relation to the thermal performance and the TAS model was deemed to be reliable through comparison with the field measurements the team conducted a simulation of the base case scenario in free running conditions during a typical cold winter week as defined in the previous section.
The resultant temperature of the base case scenario for the bedroom and living room is presented in Figure 91. It was chosen to look further into the resultant temperature which is a combination of the air temperature and the mean radiant temperature in order to get a better indication of the thermal sensation a person would have in this space (in comparison with presenting only the air temperature). It can be seen that in free running conditions both the bedroom and living room are below the comfort zone for this month. The bedroom temperature is 2 C lower on average in comparison with the living room. This result is consistent with the data loggers measurements. Therefore it was decided to concentrate on the bedroom performance as a worst case scenario in the winter week.
Figure 91: TAS simulation base case free running north apartment for a typical winter week (04/01 - 10/01)
Next a simulation of the proposed reduction of windows as detailed in the ‘Daylight Studies’ section and shown in Figure 92 was run. Figure 93 shows the resultant temperature of this option. In it one can see that with reduced windows the bedroom temperature is higher by 2 C in average with free running conditions. In order to assess the difference in energy consumption that will incur, a simulation was run with a thermostat set for 19.5 C in the living room and bedroom, and 17 C in the bathroom and hall (which is the lowest range of the comfort zone).
Figure 92: Scheme showing window reduction
As shown in figure 94 the energy consumption is reduced by half in comparison with the base case. This result confirms the initial assumption that was made using manual calculations.
Therefore it can be concluded that the reduction in the size of the windows reduces significantly the energy consumption in the north apartment. The effect of the window reduction on the comfort levels was assessed in the summer scenario and it is described in the next section of the report. The next research question formulated was: - Can the energy consumption in the apartment be further reduced? How? Comfort Zone
An assumption confirmed by MIT calculation was that if the windows would have had higher thermal resistance values the energy consumption would have been lower. Hence, the team decided to introduce shutters on the windows, that could be closed at night time thus resulting in a reduced overall U-Value of the opening, at a time when the external temperature is lowest and windows are not beneficial in terms of views and daylight. Figure 95 shows the change in the resultant temperature in the room when the night shutters are closed between 5.00 pm and 8.00 am. In average the resultant temperature is higher by 1 C in comparison with the reduced window scenario. The energy consumption is reduced to 3.3 (kWh/m²). Page 49
Figure 93: TAS simulation parametric studies for free running north apartment for a typical winter week (04/01 - 10/01)
During these investigations two further questions were raised: W/m ²
N Figure 94: Location of data loggers in the apartments and in respect to the residential block
Figure 94: TAS simulation for the base case free running north apartment without heat recovery system for a typical winter week (04/01 - 10/01)
Since currently in the apartment there is only one thermostat and it was found in the field studies that residents usually had the thermostat set to 22 or 23 C the team wanted to check: - How is the thermostat setting affecting the energy consumption? Secondly the team wanted to better understand: - What are the implications of the heat recovery system on the energy consumption? Figure 94 shows the difference in temperature that occurred when the base case was simulated with and without the heat recovery system. On average without the heat recovery system the temperature is lower by 1.3 C in the living room and the bedroom. Figure 95 shows a comparison of the energy consumption between these scenarios and the base case.
In the base case scenario when the thermostat is set to 22 C in the whole apartment the annual energy consumption is higher by 40% (8.2 kWh/m2 ) compared to the previous settings. 5.5 (kWh/m²)
The annual energy consumption without the heat recovery system would be higher by 64% (7.4 kWh/m2) in comparison with the base case (for a thermostat set at 19.5C in the bedroom and living room and 17 C in the bathroom and hall). The team concluded that:
Base Case 19.5 C and 17 C
Base Case with no heat recovery system Thermostat 19.5 C and 17 C
Base Case Base Case Thermostat 22 C with windows reduced Thermostat 19.5 C and 17 C
Figure 95: Energy consumption for the different scenarios
Base Case with windows reduced and night shutters Thermostat 19.5 C and 17 C
- The energy consumption could be further reduced reaching a low level of 3.3 (kWh/m2) by using night shutters. - The thermostat settings were found to be very significant in terms of energy consumption. - The Heat recovery system was found significant in contributing to lower energy consumption. Page 50
Figure 96: TAS simulation for the base case north apartment living room for a typical summer week (09/08-15/08) Summer week Continuing from the winter study (page 49), a simulation was carried out to assess the thermal performance in the summer conditions. MIT preliminary calculations indicated that the apartment overheated significantly in the summer if no extra ventilation is provided (in addition to the fresh air requirements). However with 10 ac/h throughout 24 hours, the mean temperature could be kept within the comfort zone for an external temperature of 25 C. TAS simulation that was conducted confirms this preliminary indication. As shown in figure 96 in the base case scenario the apartment overheats with an average resultant temperature of 34 C and 32 C in the living room and bedroom respectively for the summer week. Since the living room temperature was consistently higher in relation to the bedroom it was decided to concentrate in the former’s performance as it is established as the worst case scenario for the summer week.
N Figure 98: Location of data loggers in the apartments and in respect to the residential block
Figure 97 shows that with windows opened 80% from 7.00 am to 7.00 pm the apartment can be kept within the comfort zone. As an indication the graph also shows the resultant temperature in the living room with windows opening 80% only at times of occupancy. It was concluded that with natural ventilation the apartment can be within the comfort zone, but in summer the ventilation required is extensive.
However observations during the field studies showed that opening the windows for long periods of time could incur disturbance due to noise. In addition since the windows open inward it is an issue to leave them opened in due to rain possibilities. Pollution could also present a problem in this location. It was therefore concluded that better conditions and mainly more choices would have been given to the residents if the apartments were designed to minimise unwanted heat gains. Page 51
Livingroom Resultant Temp with windows opening 80% at Occupancy Times (C)
Figure 97: TAS simulation for the north apartment base case living room with opened windows for a typical summer week (09/08-15/08)
Livingroom Resultant Temp with windows opening 80% 7am-7pm (C)
Figure 100: TAS simulation for parametric studies in north apartment living room for a typical summer week (09/08-15/08)
In light of these observations the team proceeded to investigate the following: - Could unwanted heat gains be reduced in the apartment? How? The results of the simulation are shown in figure 100 The following parameters were checked: 1 - Reduction of windows as shown in figure 101 and detailed in the ‘Daylight Studies’ section. A reduction of 1.2 C in the resultant temperature was achieved.
2 - Ventilation of the building corridor with10 ac/h. Further reduction of 1.1 C in the resultant temperature was achieved.
Figure 101: Schemes showing window reductions
During the field studies it was observed and measured that the corridor reached very high temperatures. Therefore this proposal would be beneficial not just in the context of the apartment but also of the building. Furthermore temperature levels closer to the external temperature in the corridor, as illustrated in Figure 99, would create a better transitional zone and improve the comfort feeling in the apartment by preparing the body gradually temperature change between indoors and outdoors. 3 - Using the night shutters that were proposed in the winter scenario as day shutters for the summer kept closed between 11.00 am and 4.00 pm. Further reduction of 2.4 C was achieved. In addition to this set of runs the amount of ventilation required in order for the apartment to be in the comfort zone was checked. It was found that with 30% opening of the windows during occupancy times the temperature was within the comfort level as seen in Figure 102.
Figure 99: Section through apartments block showing lower temperatures in the common areas
Following this set of simulations the team concluded that: Reduction of overheating by 4.7 C could be achieved with the following means: - Reduction of window size - Corridor Ventilation - Introduction of day shutters
As a result opening windows for cooling purposes is required for less time which gives the residents more flexibility. Comfort Zone
Figure 102: TAS simulation for parametric studies in north apartment living room for a typical summer week (09/08-15/08)
This is beneficial in this urban location where the opening of windows present a disturbance at times. Page 52
SOUTH APARTMENT - SHADOW MAPPINGS Source Ecotect
For better understanding the solar exposure of the south facing apartment along the year, nine shadows diagrams were plotted showing three days and seasons: Winter Solstice, Spring Equinox and Summer Solstice. On the 21st of December, the apartment facade is shaded for the most part of the day due to the low solar angle due to obstructions by surrounding buildings. During this day the apartment is only exposed to the sun around for one hour at 12:00, and the solar radiation is highly desirable since it can contribute to reduce the heating demand. During the Spring Equinox the sun is high enough to strike the apartmentâ€™s facade during the entire day. At 12:00, both the bedroom and the living room are well lit. In the afternoon, the kitchen area and the living room are very exposed to the sun, due to the large windows in the winter garden. On June 21st when the sun is in the highest angle, the facade of the apartment receives direct solar radiation from early in the morning to late in the afternoon. This fact in combination to a high proportion of windows (57% of the envelope area) may indicate the necessity of solar control in order to avoid unwanted heat gains that can lead to overheating in the summer. Page 53
Figure 103: Sun trajectory with respect to the building showing the south apartment
Figure 104: Sun path affecting the south apartment calculated with Ecotect
Figure 105: Solar rays study Page 55
SOLAR CONTROL - SOUTH APARTMENT
In pursuit of finding the best shading device to provide an efficient solar control to the apartment, Ecotect was used as tool to plot the solar rays for a given hour in the Winter Solstice, Spring Equinox and Summer Solstice. As shown in the shadows’ diagram, 12:00 is an hour in which the apartment is exposed to direct solar radiation during the entire year. This way it is possible to see how sunlight comes into the apartment and how it is being reflected by the different internal surfaces. The current scenario (base case) shows that the apartment is receiving a high amount of direct radiation throughout the year. After testing different types of shading devices, the overhang seems to be the most efficient one for south facades. One of the main factors which drove the team to this conclusion is that unlike the horizontal louvres, it doesn’t avoid the useful solar gains in the winter when the angle of the sun is lowest. Nevertheless, a well dimensioned overhang according to the size of the window can block the direct solar radiation in the summer when the solar angle is higher, as shown in the Figure 105. As a proposal to improve the windows’ design, the first approach was to increase the height of the sill, since this was one of the main complaints of some current residents. Consequently the size of the windows was reduced, achieving a better window to floor ratio. In addition the crossing bars were removed to allow the windows to open outwards. This way it is possible to use the blinds to avoid glare while the windows are fully or partially opened. Hence, a 900mm length overhang was necessary to create proper shading for the summer. Figure 106: Solar rays study
DAYLIGHT FACTOR ANALYSIS - SOUTH APARTMENT As part of the exercise, a reduction of the window to floor ratio of the flat to achieve a better energy performance was considered. Radiance was used to show how this decision would affect the daylight factor in the apartment rooms. Figure 107 shows that in the base case, the apartment has in general a high daylight factor rate in the living room and in the bedroom. The average daylight factor in the flat is 6, 2 % (without considering the winter garden) which is right above the minimum required by the British Standards. The next step was testing the 25% window to floor ratio. For this, one of the full height windows facing the winter garden was blocked and one of the three windows of the bedroom was removed. These changes combined with the installation of an overhang and the current plan configuration of the rooms, resulted in a significant reduction in the overall average daylight factor in the flat, which in the kitchen couldnâ€™t reach the minimum 2% recommended by BS 8206. So after running various simulations, the best ratio achieved was 34% as shown in the Figure 108. The change proposed in this option was basically increasing the height of the sill to 800mm in all the windows including the full height windows of the balcony. This way an average daylight factor in the kitchen area of 3.2% was achieved along with a more even distribution of light in the rooms. Page 57
Figure 107: Daylight factor plans calculated with Ecotect
SOLAR RADIATION After establishing the proper window size in relation to it is floor area for this apartment, another Ecotect simulation was conducted with the purpose of having a more accurate assessment concerning the efficiency of these changes in combination with the overhang, therefore reducing the direct solar radiation during the summer months. The results show the resultant average daily solar radiation for the month of June. The Figure 108 confirmed the statement of Arupâ€™s engineer that the crossing bars in the current windows, besides having an aesthetic function, can also help in reducing the direct solar radiation in the glass pane during the summer when higher solar angles are found. Nevertheless, due to the 1900mm height of the windows, a major part of the pane is still exposed to radiation levels higher than 2000 Wh/m Â˛. Hence, one can conclude that the effectiveness of those bars in terms of preventing undesirable solar gains is fairly limited. The base case simulation also show that the large glass panes which divide the living room with the winter garden is already well protected, eliminating the necessity of using an overhang in this area. As seen in the Figure 108, the overhang is creating enough shading for the windows during this month, reducing considerably the incident radiation.
Figure 108: Solar radiation study on the facade calculated with Ecotect
ANALYTIC WORK – TAS SIMULATIONS - SOUTH APARTMENT
The main question which drove the team to conduct this analytical work was concerned with the adoption of air-conditioning as a cooling solution for this apartment. As it is known this type of solution increases considerably the energy demand of the building contributing this way to higher CO² emissions and consequently to global warming. Hence, the first simulation is investigating what are the summer temperatures in the apartment under free running conditions when the windows are closed and how a proper facade design and shading is helping to minimize the cooling load. The second simulation will assess what are the minimum levels of natural ventilation necessary to bring the temperatures to the defined comfort zone. The simulations were run in a typical week of august, in the living room of the apartment, which is more exposed to direct solar radiation. All the construction inputs used were the same as in the north facing flat as well as the internal conditions since both flats have almost the same appliances and the dwellers have similar occupancy patterns. The fresh air provided for these simulations was 36 m³ per hour per person.
Resultant Temperature ° C
As seen in the Figure 109, the high solar gains in the base case scenario are increasing the temperatures in the living room to up to 40 C during day time. When the windows are diminished, following the 34% window to floor ratio, the maximum temperature drops around 2 C. However, when the overhang is included in the simulation the temperatures were reduced to almost 30 C in the warmest days. It is a significant drop, but is still 4 C above the comfort zone. Figure 109: Free running summer temperature simulation for the ninth to fifteenth of August. Generated with TAS
The team concluded that reducing the internal temperatures of the apartment by adding an overhang is the first step to avoid the use of Air conditioning in this apartment. This way, lower levels of natural ventilation are required to provide comfort and the occupants can have the windows opened for shorter periods of time or even leave them just slightly opened when they are not at home, which is a good solution for the problem of noise. The current annual cooling load for this apartment is 50.27 Kwh/m2 (Thermostat set on 22 C). This would be the amount of energy saved by applying the mentioned improvements.
0.3 Aperture Factor
0.9 Aperture Factor
Figure 111: Different aperture values for the windows Page 59
Resultant Temperature ° C
For the next simulation (Figure 110) the windows were considered opened from 10:00 to 19:00, which are the hours when the resident is not at home during week days, so he wouldn’t be disturbed by the external noise. In the base case run, the windows of the living room were fully opened (1.0 aperture factor) and it still wasn’t enough to reduce the temperature in order to bring it to the comfort zone during the warmest days of the week. There is also a problem with having the windows fully opened in London, where heavy rains are likely to occur. In the simulation of the improved scenario, the windows are only tilted (0.3 aperture factor) and the temperature in the flat reaches the comfort zone during the entire week, apart from few peaks that can be controlled by opening the windows fully.
0.3 Aperture Factor
0.9 Aperture Factor
Figure 110: Free running. Summer temperature simulation for the ninth to fifteenth of August + apertures. Generated with TAS
Resultant Temperature ° C Figure 112: Free Running. Winter temperature simulation for the fourth to tenth of January. Generated with TAS
Annual Heating Load
The architects stated that the purpose of the glass louvres in the winter gardens was to avoid the wind during the cold seasons. However the team raised questions to determine wether they could also perform as thermal buffers, increasing the temperature in the living room during the winter by reducing the heat loss and also minimizing the heating demand of the apartment. The simulations conducted for a typical week of January under free running conditions seek to answer these questions and also check how the reduction of the window to floor ratio to 34% is improving the apartment performance in terms of comfort and energy consumption. The infiltration rate considered inside the winter garden was 0,7 ACH, because it is not completely sealed. Moreover the temperature simulations considering this rate approached the temperature from the spot measurements for the same day and hour. Also, a 0,2 ACH infiltration rate was considered inside the apartment. As shown in the figure 112, the temperatures in the living room for the base case scenario are below the comfort zone. When the winter garden louvres are closed, the average temperature rises by 1, 5 C. Considering the windows reduced, the temperature reaches the lowest level of the comfort band for most of the days in this week. The last improvement was to add night shutters, which brought the temperatures of the living room into the comfort zone in throughout the week. Hence, one can conclude that with the before mentioned improvements, no additional heating is required in this apartment. Nevertheless, the minimum temperature for the thermostats reported by the building residents in the winter was 22 C which is the upper limit of the comfort band. The final simulation is showing how much energy consumption the flat is requiring setting the thermostat on 22 °C, which is 11,5 kWh/m². This demand could be lowered to 5.9 kWh/m² by reducing the thermostat temperature to 19.5 °C in the living room and bedroom and 17 °C in the bathroom. Adding all the improvements mentioned in the comfort studies the annual heating demand would drop to just 1,77 kWh/m², which is a very low rate (figure 114).
Figure 113: Picture of the winter gardens
Figure 114: Annual heating loads for the different case scenarios
CONCLUSION The building is a commercial building that creates a public â€˜piazzaâ€™ in a place that was previously not accessible to the public thus connecting parts of the city that were disconnected before and therefore contributes to the urban fabric and the opportunities that could be created there. The design achieves a ground floor that is almost transparent, creating a dichotomy with its density. The transparency achieved with the 6 m tall double glazed, floor to ceiling windows allows views through the building volume from one street to the opposing one. The massing of the building enhance the urban connections by creating views and passages through the building. The treatment of the sloping of the piazza is also commended with a height difference of 2 m from one side to the other. As a result, a new public area that is very accessible is created in a central urban zone by a commercial building. The team sees this as a great achievement on behalf of the design team. In addition the glazed terracotta that is used in the courtyard facades with its light gray colour creates a pleasant daylight distribution in a courtyard that is quite small with a narrow section. The building achieved a BREEAM excellence rating, and was designed with higher specifications than the Building Regulations required at the time. It is however almost fully air-conditioned in a climate that is most of the year below the comfort zone. Most of the office building has a deep plan and the overall volume of the building is significantly denser than the previous building thus overshadowing adjacent buildings. The architect had a clear agenda in relation to the massing of the building and the creation of a piazza and has successfully convinced the client to introduce certain aspects that would have otherwise not been added to a commercial building. It can also be said that the building has a high standard of specification with good building materials, high standards of thermal resistant, good levels of air tightness, a high plant efficiency and so on. These were driven by the design team, by regulations, by the local authority requirements and by the demands from potential buyers and state agents. It is to this end that the building is deemed as sustainable. However, with regard to one of the most important issues towards environmental impact, air conditioning use the design adopts an almost fully air conditioned solution. Therefore, the depth of the plan was forfeited as well as the possibility of coupling with the exterior. It seemed to the team that perhaps the concept of transparency that was applied in the Ground Floor could have been extended further to the environmental aspect and provided a real transparency, coupling and connection between the inside and the outside. Such connection could have benefited the indoor environment in a moderate climate, thus requiring less energy for heating or cooling. Allowing for natural ventilation while minimising heat losses and unwanted heat gains. Page 61
The apartments have generally good energy performance and about half of them are naturally ventilated. The other half could just as well be, with little design variation. The views that are provided from the apartments also contribute to the satisfaction, and the location in a central urban area contributes to mitigate use of transportation and to a bigger variety of urban life. The apartments are designed with almost identical elevation to the offices apart from adjustment of the height of the windows. This is resulting in a shape and size of glazing which conveys unnecessary heat gains and heat losses. These windows retain the same size throughout all the orientations, suggesting that facades were designed independent of their orientation. The report shows that by applying shading devices in the south apartment, combined with a proper window design the demand for cooling in the summer could be reduced considerably and minimize the amount of air changes per hour necessary to bring the internal temperature to the comfort band. this could give more flexibility to the residents in opening windows in a site in which this could cause disturbance of noise at times. In addition necessary precautions could have been to place the apartments in a better location in terms of noise, or orient all the bedrooms overlooking the courtyard which is sheltered from noise. The energy consumption as a result of heating could also be reduced with more appropriate window size and use of night shutters. Finally, ventilation of the corridor in the apartment block can improve the conditions in the apartment (avoiding some over heating) and creating a transitional zone that prepares the body for the change in temp from inside to outside gradually thus contributing to more comfortable conditions. Page 62
Berglund,B et al (1995). Guidelines for Community Noise World Health Organization Press, Geneva. Building Regulations( 2006). Part F. Ventilation. Published by NBS for the Office of the Deputy Prime Minister. CIBSE (1999). Lighting Guide LG10. Daylighting and Window Design. Chartered Institution of Buildings Services Engineers, London. CIBSE (2006). Guide A. Chartered Institution of Buildings Services Engineers, London. Szokolay, S. (2003 / 2008). Introduction to Architectural Science. The basis of sustainable design. Architectural Press. Yannas,S. (1994). Solar Energy and Housing Design. Volume 1: Principles, Objectives, Guidelines. AA publications
Architectural Association School of Architecture - London. Fieldwork and Environmental Assessment: Study of the indoor and outdoor environm...
Published on Feb 23, 2014
Architectural Association School of Architecture - London. Fieldwork and Environmental Assessment: Study of the indoor and outdoor environm...