BUILDING SCIENCE 1 (BLD60803) PROJECT 1 : Case Study: Identifying Innovative Passive Design Strategies
LIM FOU SING 0314997
TAN KWOK SEONG 0314700
LEE RUN SEN 0308226
CHENG CHEN LIANG 0310043
TSAI WAN CHING 0315185
LIM SHU YIN 0307795
National Library, Singapore
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CONTENT PAGE 1.0 INTRODUCTION - 1.1 Brief Introduction - 1.2 Purpose of Study - 1.3 Location of Site - 1.4 Awards & Accolades - 1.5 Purpose of Singapore’s National Library - 1.6 Orthographic Drawings 2.0 CLIMATE DATA 3.0 THERMAL ANALYSIS - 3.1 Thermal Data - 3.2 Relationship Between Temperature & Humidity - 3.3 Comfort Zone 4.0 WIND ANALYSIS - 4.1 Wind Data - 4.2 Wind Studies - 4.3 Rose Diagrams - 4.4 Air Circulation - 4.5 Natural Ventilation 5.0 SUN ANALYSIS - 5.1 Solar Data - 5.2 Natural Lighting against Sun Path - 5.3 Building Configuration against Sun Path 6.0 DESIGN CONCEPT & PASSIVE DESIGN STRATEGIES - 6.1 Psychrometric Data - 6.2 Building Envelope - 6.3 Passive Design Strategies - 6.4 Identification & Analysis of 2 Passive Design Features - 6.4.1 Light Shelves - 6.4.2 Thermal Chimney 7.0 Active Design Strategies 8.0 Conclusion 9.0 References
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1.0 Introduction 1.1 Brief Introduction The National Library of Singapore was designed by T.R. Hamzah & Ken Yeang Sdn. Bhd. which consists of two 16 storey blocks and three basements. There are several libraries which named the Central Public Library in Basement 1 and the Lee Kong Chian Reference Library from Levels 7 to 13. Besides, the library is equipped with facilities such as the Drama Centre located at Levels 2 to 5, which is managed by the National Arts Council. There is also a closed viewing point called “The Pod” located on 16 th floor. It is a venue built especially for functions and events. As a green design feature, there are some gardens full of greenery planted around the building. The public are allowed to access the Sky-Park on Level 5 and the Retreat on Level 10 which offers a great panoramic view to the city. There is also a big space called “the Plaza” beside the lobby that functions as exhibition space. As one of the iconic building in Singapore, National Library of Singapore is being environmentallyresponsive designed as an ecological approach adapted to the use of energy and materials. Due to its remarkable green design, the building won the 1st prize in the ASEAN Energy Efficient Building Awards in the New and Existing Buildings Category. Besides, it was awarded the Green Mark Platinum Award in the Building and Construction Authority of Singapore (BCA), the top h onor bestowed on “green” buildings. The building has innovatively employed bioclimatic techniques to prototype the environmentally responsive tropical design. Bioclimatic techniques employed include climatically-responsive building orientation and built form configuration, responsive facade design, appropriate building color, passive low-energy systems, passive lighting concepts and the extensive use of landscaping. These techniques have become a collective strategy for energy efficiency.
Figure 1 & 2: Main Facade of National Library Singapore from North (Left) and North-East (Right)
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1.2 Purpose of study The purpose of study is to identify and define the principles of heat transfer in relation to building and people. Throughout the process, we would be able to understand what is thermal comfort, the effect of thermal comfort factors to a person in a space, and also to study about MS1525, UBBL, GBI, and Green Mark Standards which encourage the design, construction, maintenance of new and existing buildings in a manner that reduces the use of energy. On the other hand, we would be able to identify the environmental conditions related to the site conditions, climate and so on (Wind, Solar, Weather, etc.). Starting from the analysis of country’s climate by using Ecotect. Followed by further analysis of the chosen building about their passive and active design strategies. The pictures below show the site context of the library, which interrelates part of the analysis of the library.
Figure 3: Site Context of National Library
Figure 4: Bird’s Eye View from the Roof Garden of the Library
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1.3 Location of the site The National Library building enjoys a commanding presence in the Bugis-Bras Basah district of Singapore. Its location in the tropics and the unique requirements arising out of climatic conditions in the tropics served as the criteria for design. That would means that the building would embrace the Asian worldview of the environment and serve as an icon for the region and a library for Asian to appreciate their diverse culture. Situated on an 11,304 square metre site between Bugis Junction and and Bras Basah Complex at 100, Victoria Street, the current building has replaced the old National Library at Stamford Road. Its location is rather strategic for public access due to the nearby MRT station which are Bugis MRT Station and Bras Basah MRT Station.
Figure 5: Site Context of National Library via Plan View
Figure 6: Location Map of National Library
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1.4 Awards & Accolades In recognition of its environmental friendliness, it was awarded the Green Mark Platinum Award in April 2005. This is the highest honour for green buildings in Singapore granted by the local Building and Construction Authority (BCA). The building received re-certification of the Green Mark Platinum Award under the “Existing Buildings” category in March 2009 . The building also won first prize in ASEAN Energy Efficiency Award and Singapore Silver Award in the Universal Design Award from BCA, for its wide spaces, accessibility, clarity in way finding and accessibility. As a result of its 'green' fame, National Library Building (NLB) has received many visitors from various countries, including the United States, Thailand, Indonesia and India, to look at the 'green' features of the National Library Building. These visitors have been impressed with the extent of planning and implementation of the 'green' features in the building while ensuring good indoor air quality. We also have visitors, including students and academics, from local and overseas educational institutions, interested in the 'green' aspects of the building.
1.5 Purpose of National Library Singapore National Library Singapore was built to develop an adaptive public library system that would bring library and information services closer to the community. It creates a network of borderless libraries to enable the access to information and resources from anywhere and anytime. It provides quality service through market orientation where a wide range of service will be introduced. National Library Singapore also build symbiotic linkages with business communities and other community group in society.
Figure 7: Lobby as a public information inquiry centre
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1.6 Orthographic Drawings
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2.0 Climate Data Diurnal Average Temperature 1 Jan to 31 Dec Diurnal temperature is the difference between the daily maximum and minimum temperature.
Table 1: Monthly Diurnal Average – Singapore
Dry Bulb Temperatures 1 Jan to 31 Dec They Dry Bulb Temperature refers basically to the ambient air temperature. Its measured by a thermometer which is not affected by the moisture of the air.
Table 2: Monthly Dry Bulb Temperature – Singapore
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Wet Bulb Temperatures 1 Jan to 31 Dec The wet bulb temperature is the temperature indicated by a moistened thermometer bulb exposed to the air flow. It will always be lower than dry bulb temperature but will be identical with 100% relative humidity. Table 3: Monthly Wet Bulb Temperature – Singapore
Direct Radiation 1 Jan to 31 Dec Direct radiation data is used for the calculation of evapotranspiration, which is a function solar energy, wind and temperature.
Table 4: Direct Solar Radiation – Singapore
Relative Humidity 1 Jan to 31 Dec Relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity, to see how much air is saturating with water vapor, which is to check the possibility of rain.
Table 5: Monthly Relative Humidity – Singapore 7
3.0 Thermal Analysis
3.1 Thermal Data
External Temperature
Table 6: Monthly Diurnal Averages of External and Internal Temperature
Internal Temperature
The temperature of the building’s site during day sits about 35 °C and 29°C during night . Factors such as climate affect the temperature of the library. Various considerations were placed into regulating the temperature on both the interior and exterior of the building. The interior walls have a temperature of 28°C for exposed areas and 24°C for unexposed areas. Due to the designing of landscape, by inserting greeneries in between few floors, allowing the local vegetation shades to reduce the heat and effectively lowers wall surface temperature by 17°C. Evapotranspiration cooling is also adapted in the building, lowering air condition cost by 25%-80%.
Figure 8: Greeneries in Various Floors of the Building Help with Evapotranspiration Evapotranspiration Cooling
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3.2 Relationship between temperature and humidity Relative Humidity
Table 7: Relative Humidity of Singapore The relative humidity typically ranges from 62% to 98% over the country of the year. 62% consider as mildly humid while 98% consider as very humid. From the graph we obtained above, it can be seen that February would be the driest month, whereas November would be the most humid month for Singapore. But the graph above shows only the average daily high and low relative humidity (blue and brown), its more likely to be within both graph, where the percentile bands are.
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Table 8: Temperature of Singapore – 22nd April 2014
Table 9: Humidity of Singapore – 22nd April 2014 The graphs above show the temperature and the humidity of Singapore on the d ay we visited, 22nd of April 2014.
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Table 10: Temperature Against Humidity – 22nd April 2014
Indoor temperature is lower while outdoor temperature is higher during the lunch hour. Indoor air is cooler because human activity is lesser. The building loses the heat easily as the entrance of the building helps air ventilation from outside to inside. Besides, roof garden also has the cooling effect function. Water vapour of the plants evaporates to the air and enters through fenestration of the building. However, outdoor will become warmer as human activit1y increases. The building is facing the main road especially at peak hour, more vehicles are passing through and releasing gases like monocarbon oxide and carbon dioxide which will increase temperature. Indoor relative humidity is lower because the building facade prevents water vapour to enter the building. The humidity of air comes from the plants of the roof garden and fenestration of the building which is the entrance of the building. Outdoor relative humidity is higher. Plants are surrounded around the building facade, which tends to produce more oxygen outside. The difference between indoor and outdoor may not have huge difference as mono-carbon oxide and carbon dioxide would affect the overall outdoor relative humidity. Temperature and relative humidity are interrelated. For example, when temperature is high, relative humidity is low. Indoor air is cooler as all of the openings (entrance) are usually closed during the lunch hour due to less human activity. Hot air inside will rise and escape to exterior. Low humidity level is due to the poor air ventilation (limited fenestration). The analysis causes a change from the typical theory of relationship between temperature and relative humidity. Therefore, occupants feel most comfortable in the morning with lower temperature and higher relative humidity.
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3.3 Comfort zone
8.00 AM
1.00 PM
5.00 PM
11.00 PM
Intensity of Use
Diagram 1: Intensity of Use in the National Library in Relation to Time
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A basis of human comfort zone requires the temperature to range about 24°C. 24°C. Weather, humidity, pressure and number of occupants in a space affect the thermal factor of the building. Analysis shows that the peak hours in the library are around 9am and 5pm, where the spaces in the library are packed. However, between 12 and 2pm, the chart shows that the number of occupants decreases. Number of occupants in exterior reading spaces viewing pod reduced whereas more people occupy the middle floors, bar and cafe. This shows that the comfort level changes in sync with the temperature; an increase of temperature results in the decrease of comfort level. The comfort zones alternate in between the building along the time lapse of a day.
Diagram 2: Thermal Analysis of the Library Spaces The comfort zone will be alternative along with time. The drawing above shows an example of our own analysis for a certain level of the building. The colours represent the warmness of the zone, which has a direct relation with comfort zonings. The red zones are along the building as there are warmer along the building, because the building is mostly built up by glasses, allowing the sunlight to penetrate directly together with some heat (some heat were reflected and absorbed by the glass). This is the main reason why the comfort zones alternate during different hours.
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Factors affecting thermal comfort can be categorized into two main categories, which is environmental factors and personal factors.
The above diagram shows the environmental factors, which are air temperature, radiant temperature, air velocity and humidity. A good passive design building will take it considerations of all which is the reason why it’s essential to collect the data during design stage. Specifications of design strategies of the building we study have been written at next c hapter.
The another category is personal factors (human factors), which are clothing insulation and metabolic heat. These variables are dependent on the users, which cannot control by the building. For example, some clothes are thicker which have more insulation, or, some users ran across the street under the hot sun and sweat. The clothing insulation can still be control if the building specifics users to wear proper clothing (e.g. Long pants) , but the building we are studying is not required to.
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4.0 Wind Analysis 4.1 Wind Data Wind Directions over the Entire Year
Table 11: Wind direction over a year in Singapore The chart above shows the wind directions over the entire year. From the chart, we can see that the wind is most often out of the north, followed by south . The wind is least often out of the east.
Speed of Wind
Table 12: Wind Speed over a year in Singapore
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The typical wind speeds in tropical climate varies from 0mph to 14mph. The green graph represents average daily maximum wind speed , red represents average daily minimum wind speed , and the black represents the average wind speed . These data is a must to take in consideration while designing the building, especially high rise building like the National Library. The reason is because the glasses constructed with the building must be able to bear with the strength of the wind (considering the highest spe ed of the wind).
4.2 Wind Studies
January
April
December
August Diagram 3: Wind rose-diagram of the crucial months
Through the rose diagrams above, we analyze that approximately 60% of the wind comes from NorthEast, 25% comes from South and 15% comes from North-West.
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4.3 Rose Diagrams
Diagram 4: Wind rose-diagram of national library on site The wind rose-diagram placed on top of the site plan. The locations of core and spatial organization of this building was planned/designed by considering the prevailing winds, for example, the roof gardens (3rd floor, 5th floor and 10 th floor) were placed at NNE because the result shows stronger wind would have prevailed from that direction.
Figure 9: Roof gardens at different level in the library.
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Diagram 5: Prevailing Wind Rose-Diagram The rose diagram above shows the data of prevailing wind throughout the entire year. We obtain many details as we further our research specifically on our sites.
Table 13: Wind Velocity – 22nd April 2014 The diagram above shows the velocity of speed on the day we visited. The north-east wind generates the lowest velocity in the under belly at 0.5 m/s, while south-east wind generates the highest velocity in the under belly at 2.3 m/s. The ambient wind speed of National Library is 3.6 m/s. The air velocity under the belly of the building will not exceed 2.3 m/s. Where by the annual average wind speed of the plaza is -0.814 m/s.
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4.4 Air Circulation Internal Design Condition
Maximum Air Movement
Maximum Dry Bulb Temperature
Maximum Relative Humidity
25 m/min
27°C
75°C
Plan of the building
Diagram 6: Air circulation Within the National Library The diagram above shows the air circulation of the Singapore National Library. Air circulation in the building moves where wind from the outside enters one end of the street space in the building and leaves from the other end. The same circulation occurs in the void at the top of the building. Vertical air circulation also occurs in the atrium where the skylight is placed higher than the r oof with openings for warm air to escape and cool air to descend on to the floor level.
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4.5 Natural Ventilation
Section of the building
Diagram 7: Natural Ventilation within the Library
The building uses both stack ventilation and cross ventilation. - Stack ventilation: This ventilation mostly occurs in large tall spaces, it functions well to extract warm air from a space and replacing it with cool air. Stack ventilation is shown in the library building’s atrium. The over 16 storey atrium perpendicular to the tunnel-like street space below allows for warm air to rise and cool air to descend. - Cross ventilation: The pressure caused by wind against a large wide obstacle results in air being forced into any small openings found on the surface of the obstacle. The air rush enters the space and bounces off other surfaces to find another opening to leave the space. This is shown in the national library as well, in the void on the upper floor and the tunnel on street level.
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Air circulation in the atrium assist interior air ventilation and minimizes active cooling and energy consumption. The plaza located at the ground level with widely open space ensures smooth air flow and attracts cool wind into the space. Natural ventilation is applied in the main transition spaces; such include internal walkways, event plaza and courtyards. Gardens are placed facing towards the strongest wind direction in order to control the wind sp eed that enters the building.
Figure 10: Event plaza and walkway that maximize cooling effect into the space.
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5.0 Solar Analysis 5.1 Solar Data
22nd April 2014 8.00 A.M. The shadow is long because the sun has just risen up, the facade of the building is shooting by the solar rays as the angle of sun is at low angle.
22nd April 2014 10.00 A.M. The whole facade of the building is still being shined by the run, while the other side of the building is shaded by the front facade facade and the overhang. But the side fins and vegetations help a lot by providing shades.
22nd April 2014 12.00 P.M. During this hottest hour, as the sun is at its most high up spot, it’s supposed to be the hottest and brightness hour, but overhang and side fins help to protect the building by shading, yet allowing some of the daylighting to penetrate into some open air area and the middle skylight.
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22nd April 2014 2.00 P.M. The shades go the opposite way from earlier, the other side of the building is absorbing much heat and more light by now. From the way the diagram translate through shadow, the overhang on the roof seem to provide shades to the whole building already, but as there’s skylight in the middle on top, the sunlight will still penetrate through it, enable the users to enjoy sunlight comfortably.
22nd April 2014 4.00 P.M. As the solar rays shoot towards the building, there are lights which shine at the vegetation, and the horizontal louvers enable partial sunlight to access instead of blocking them with solid overhangs. And so, users can be reading books much more comfortably in open area with the greeneries around them, as well as the comfortable sunlight.
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5.1 Natural Lighting against Sun Path
General Library
150 W/sqm
Archival (book stacks)
10 W/sqm
NLB HQ (offices)
20W/sqm
Table 14: Energy Consumed by Artificial Lightings in Separate Rooms
Diagram 8: Light Diffuses through the Skylight The library was quoted ‘designed for the tropics’, as design considerations maximizes the usage of natural elements in a tropical surrounding such as sunlight, rain, temperature, etcetera. Solar heat and light were fully utilized in regulating the building temperature and lightings.
Natural lighting is an important element for a public building like the National Library, as most of the readers will be much satisfied reading under natural lighting. When sunlight enters the space through a window or skylight, it brings not only light energy (whether direct or indirect, but preferably indirect light in libraries), but also heat energy. This solar heat gain from daylight can be a burden on the building cooling system, and sunlight must be carefully controlled to avoid this.
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Skylight is a very useful daylighting roof aperture which brings in the natural lighting while reflecting the sun heat. It’s built to be small in proportion to the surface area of building, due to the consideration of the heat content of direct sunlight.
The skylight with deep adjacent diffusing surfaces is a simple technique of protecting from direct sunlight while providing non-directional, comfortable light to the space below. A 2:1 ratio of depth to width normally provides enough diffusing reflections for glare-free light.
Figure 11: Skylights in the building from different perspectives.
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5.3 Building Configuration against Sun Path
Diagram 9: Building Configuration Sunlight was found to be the most enjoyable light for reading, throughout the research. Sunlight plays a major role in green design, as it can be used to reduce the reliance on artificial lighting. Various configurations to the library’s space result in higher energy efficiency, such configurations include: - Central Lending Library The Bamboo Garden and Discovery Garden (stage for storytelling) provide sense of comfort and harmony, at the same time cool the library from the outside in, by creating a natural air-shield protecting users from solar heat. - Building Facade Modular sunshades were fabricated and coordinated with the glass curtain wall system, adapting a 30° solar cutoff, thus preventing direct sunlight. World largest sunshades of 1.8m installed from the surface of the glass buffers solar radiation and glare yet maximize daylight to enter the structure. In order to support the sunshades, the curtain wall mullion has to extend to 5.4m high and 250mm deep. In result, this has shaded up to 2.4m wide, with a 1.2 m shade inside the building. Automated drop-down blinds are activated when the sun is too low for the shades to be effective. Proper planning of design spaces in a building is important to ensure thermal efficiency. Temperature has the tendency to tamper with the ven tilation of a space. Different organization of parts in a building function to allow wind of optimum temperature to enter and at the same time insulates the building. - Core orientation The positioning of the building’s service core and lift cores serve to block direct radiation and conduction of heat into the main building. Theses spaces are wide and hollow, using the volume of air within to act as insulation of the certain face of the building. 26
Figure 12: Laneway Sunshades
Diagram 10: Sectional Diagram of Sunshades Innovative laneway sunshades between two blocks create aesthetic lightness on the curtain wall, and direct the flow of natural breezes into the plaza. These sunshades protect the north-western and southeastern facades from solar penetration. Roof canopy and louvers complete the shading system of the building.
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Figure 13: Skylight above the atrium space - Spaces The building takes the form of two blocks instead of one single compact block in order for more internal transition spaces. The library blocks optimize the use of daylighting, where natural lighting supplements artificial light at promenades and offices spaces. The skylight situated above the atrium allows more light to enter and penetrate every storey in the building.
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6.0 Design Concept & Passive Design Strategies 6.1 Psychrometric Chart
Table 15: Psychrometric Chart Psychrometric charts are graphic representations of the psychrometric properties of air. Its very helpful in troubleshooting greenhouse buildings’ environmental problems, and simply enough to determine simple solutions. Understanding the psychrometric charts helps on visualizing the characteristics of moist air, which is helpful in passive designing. The psychrometric chart is important information for passive design strategy. There’re 6 main strategy modes for passive design techniques, which are: - Passive Solar Heating - Thermal Mass Effect - Exposed Mass + Night-Purge Ventilation - Natural Ventilation - Direct Evaporative Cooling - Indirect Evaporative Cooling The chart also shows the comfort zone (Yellow), where the natural weather (Dotted Blue) is above the comfort zone, therefore, other than passive desig n strategies, active design strategies are used to mak e the users of the building to be able to stay in the comfor t zone at all times. As you can see, there’re actually 6 main passive design strategies. 29
6.2 Building Envelope
Figure 14: Elevation &Section View of National Library Building
The National Library of Singapore complies wi th the high standards of ETTV. With its interesting material selections and innovative engineering feat, the library is one of the most energy efficient buildings in Singapore until today. The building‘s envelope is mainly built of 80% glazed windows. Double glazing glass prevents energy transfer from solar radiation and ambient temperature, reduces air conditioning needs and achieves thermal comfort. The ETTV is 32.1 W/m2 and the U-value for the glass is 1.62 W/m2 k. On top of that, 19mm monolithic thick glass curtain walls are also being used as it helps reduce condensation. The Singapore National Library used green materials and specification of materials used in the designed system to reduce the impacts of use on the natural environment. The selected mat erials on specification were carpet wall fabrics and sustainable-forested local timber . Other than reducing environmental impacts, these buildings also brings out great effect for the passive design strategies, as the layer is glazed on white, the heat en ergy from the direct sun won’t conduct e asily with the wall of the building, therefore there’s still significant temperatures differences on the internal and the external wall.
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Diagram 11: Heat Movement through Double Glazed Glass The diagram above shows our own analysis about the material. Double glazed windows are windows that have two glass panels in the same frame, separated by a small s mall space that is filled with either air or a nontoxic gas such as argon. The two glass panels should be separated by a space that is twenty millimeters for maximum efficiency. Heat won’t escape easily with double glazed windows and drought will be reduced, making the overall temperature in the house more comfortable. Double glazed windows improve sound insulation by creating a barrier between the inside room and the environment outside. The airtight construction of double glazed windows creates thermal insulation . This reduces the flow of incoming and outgoing heat. Less energy is used to heat up or cool down the space, resulting in lower energy bills.
Figure 15: Double glazed windows are used for the building facade. 31
6.3 Passive Design Strategies Passive design strategies are the strategies while designing a building, which results on a building that simply works on its own. The plan, section, s election of materials and siting create a positive energy flow through the building and save energy. Through Singapore follows the LEED green marking, but we believe the factors which influenced passive design strategies are the same with MS1525, therefore the below factors have been analyzed and written through referencing both LEED and MS1525.
The architectural consideration in designing this building is strongly influenced by its responsiveness to the immediate environment. As for the National Library of Singapore, the factors which were considered in the design are:
A) Building Orientation As a tall building exposed to the full impact of external temperature and radiant heat, the National Library of Singapore is orientated towards the North-East direction which is away from the East-West sun. Besides, the cuboidal building has four corners which each points towards north, south, east and west, thus the main surface area of the facade receives less heat and glare. The building’s service core located at on the S outh-West and North-West sides of the building serve as buffer zones to insulate the internal area. This is where the main library floors are located; the glass curtain walls are screened to provide shade and at the same time allow sufficient light to enter.
The lift core located on the North-East facade also acts as a heat shield against the afternoon sun. The adjacent block is also effective in preventing heat conduction and radiation. The West face of the building has the most sun-shading features as an additional shield against solar heat gain and glare. Low-emissive double-glazed glass panel facade and large overhangs on the external facade are the sun-shading features used. With these, the building is able to minimize glare from the rising sun in the morning and the setting sun in the evening while still manages to harvest maximum natural sunlight into the building.
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B) Building Configuration (Geometry & Layout) The Singapore National Library possesses a fairly unique yet interesting geometry and layout. From aerial view, the building configuration forms a letter “K” . The layout is configured in such a way as it symbolizes “Knowledge”. But aside from symbolism, this unique geometry helps to redirect sun rays and keep the building cool. With such form factor, it also helps prevent heat island effect. The configurations of the service area are located on the South-West and North-West sides of the building, serving as buffer zones to insulate the internal areas.
C) Ventilation The National Library of Singapore features an open Plaza area at the first storey admits natural ventilation and daylighting. Stack effect at the open Plaza happens when the air from the sides of the building is drawn upward between the link bridges and in-between the two blocks. Cross ventilation is also found in the building. The pressure caused by wind against a large wide obstacle results in air being forced into any small openings found on the surface of the obstacle. The air rush enters the space and bounces off other surfaces to find another opening to leave the space. This is shown in the national library as well, in the void on the upper floor and the tunnel on street level.
D) Floor to Ceiling Height Different floor to ceiling height is being used throughout the library based on the function function of space. For instance, the study area has got a total 5.4m floor to ceiling height. This enables visitors to study in a comfortable and spacious area. Besides it ensures visitors to be in thermal comfort as it allows ample air flow even during peak hours with a huge crowd in the library.
E) Location of Cores As a national library, the building’s cores are the study areas. The building circulation is characterized by simplicity. The building’s comprehensible design allows ease of navigation and convenience in daily use. Core elements on the typical floor consist of lifts and lift lobbies, stairs, toilets, M&E spaces and shafts. In the National Library of Singapore, all study areas were placed away from the main facade of the building, instead the study areas were placed along the skylight area to ensure study areas always remain within thermal comfort yet still receiving the nece ssary light source from natural sunlight. And the core structures that is supporting the building are steel frames and columns located all over the exterior of the building.
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F) Building Facade The facade of the Singapore National Library is one of the most interesting parts of the building. The facade is 80% made out of glass and finished with modular sunshades fabricated and coordinated with curtain wall system as well as internal partitions. The glass is double-gazing glass, therefore allowing ample natural light to to penetrate while deflecting unwanted heat rays. rays. And the facade also features a 100m high atrium which functions as a thermal stage over the internal streets, forming a naturally ventilated transition space which cools visitors before they enter the building.
G) Internal Layout The internal layout of the library is fairly interesting too. Most of the spaces were placed near the windows, especially the study compounds. This method of layout is to minimize active lightings in the building and fully utilize the light source harvested from the skylight and massive glass facade.
H) Fenestrations The openings of the National Library of Singapore can be found all around the building. But to be a little more specific, a majority of huge double-glazed glass panels were placed facing the North-East direction. This is to harvest more natural light from the morning as the sun rises.
I) Building Materials The library is mainly built up of glass, steels and polypropylene. White polypropylene shelves reflect and redirect sunlight to maintain thermal comfort in the building. Double-glazing glass windows allows maximum light source to penetrate but still blocking out heat. Steels serve as reinforcements for the entire building.
J) Roof Design & Color The National Library of Singapore provides several roof gardens in order to block heavy wind from the North-East and also cut down on direct sunlight penetration . Besides, it also serves as an environmental friendly shading to the interior. Other than gardens, the roof features 3 massive skylights to lighten up the center of the building. This helps to cut down in artificial lightings.
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K) Landscaping & Shading
A distinctive feature of the National Library Building is the practice of bioclimatic features, where the structure maintains a certain amount of connection with nature. The National Library Building also comprise of several horizontal and vertical landscaping, in the form of gard ens, terraces and sky gardens. The presence of greeneries in the 16 storeys built form induces harmony between the rigid qualities of manmade structure with natural elements and mini ecosystems. These landscaping covers 8,000 sqm of the gross floor area of 58,783 sqm, successfully reduces the artificiality of the structure. Landscaping for bioclimatic use being a distinguish feature of the library, it has encourage the public to follow suit to reduce urban heat island and energy consumption. The sky gardens and terraces are strategically placed on balconies to serve as effective heat shield, acoustics as well as to reduce glare. The local vegetation shades heat absorbing surfaces and effectively lowers wall surface temperature by 17°C. Evapotranspiration cooling is also adapted in the building, lowering air condition cost by 25%-80%. The library is situated in a fairly extensive landscape. With sky terraces and roof gardens fully utilized, local ambient temperature is lowered. The library features numerous light shelves and louvers. Light shelves shade the building with the self-shading technique and shelves that extend into the library space reflect sunlight further into the building. This optimizes daylight and thus reduces the use of artificial lighting. The louvers shades the plants in the garden and it also act as a wind buffer to slow down heavy wind.
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6.4 Identification & Analysis of 2 Passive Design Features By researching and analysing the library, we have identified numerous passive designs (as stated in 6.3 Passive Design Strategies, page32). But to highlight and have a more in-depth analysis on 2 specific passive design features, we have narrowed them down to the 2 most innovative and prominent features from the National Library itself. One of which is the light shelves which are probably the most noticable feature, redirecting and deflecting amper natural sunlight into the interior of the building. The other one was the thermal chimney that is located in the centre of the building (the plaza). It naturally activates the stack ventilation effect and provide smooth air flow in the plaza.
Selected Feature 1: Light Shelves
Selected Feature 2: Thermal Chimney
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6.4.1 Passive Design Feature - Light Shelves Shelves The National Library of Singapore has many passive design strategies implemented into the building, but one of the most prominent ones is definitely its light shelves that could be easily identified at first glance.
Figure 16: Light Shelves Seen from within the Library
Definition of Light Shelves: A light shelf is a passive lighting strategy where a horizontal or angled or even slightly curved surface is placed over building openings higher than eye level to reflect daylight into the ceiling thus bringing light further into buildings. Light shelves have been featured in many buildings all around the world in many variants in term of surface material, size, angles of placement and adjustability. Some light shelves are non-adjustable fixtures while some are adjustable (usually automated) to create different angles of the reflecting surface to maximize the amount of daylight that enter the building throughout the day depending on the sun position. Light shelves can work on their own, but they are often paired by external shading device that is placed at the same level of the internal shelves. The external shading reduces glares from the windows.
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Diagram 12: Section of Light Shelves
Reason of choice: The design team did not resort to the usage of light shelves blindly. Light shelves were carefull y chosen as one of its main green passive feature beca use the design team had to address a huge challenge which is to shade the building yet maximizing natural sunlight. To reduce solar heat gain through the facade, the building had to be heavily shaded. A 30° solar cutoff (over hang) was adopted. When the sun is 30° and more above the horizon, no direct sunlight should be visible in the building. While almost no direct sunlight should enter the building between 10am to 4pm, the facade design had to allow for the penetration of as much sunlight as possible to minimize the use of artificial lighting. As a solution, the team designed some of the world’s largest sunshades on a curtain wall, accomplishing a facade engineering feat. These sunshades (light shelves) project up to 1.8m from the surface of the glass. Installed around the entire building perimeter, these sunshades effectively control solar radiation and glare yet maximize daylight.
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Diagram13: Comparison of Daylight Entering the Building With and Without Light Shelves
Advantages: - They proved to increase the amount of daylight that enters the building thus increasing visual comfort . - They are relatively easy to install and sold as prefabricated units with own light weight support or bracketing system. - Made of composite aluminum, the light shelves are light and easy to handle. - Different variety of surface options from Matt, perforated or even corrugated. The differ ent texture gives a different level of total reflectance of the sunlight and also light diffusion intensity. The surface comes in different paint finishing too.
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Disadvantages: - In the tropical context, the biggest concern about using light shelves is the obtained heat gain. There seem to be some conflicting opinions whether to use or not to use light shelves in tropical buildings. A light shelves assessment study for hot and tropical climate done by Irving Montanar Franco, Phd shows that in comparison with standard horizontal shading devices, using light shelves do increase heat gain. Using light shelves however do not consider to be resulting in over-heating. Franco pointed that in comparison with non-shaded glaze facade, the heat gain obtained from using the light shelves is lower. - Light shelves do not perform well during cloudy days . Simulation study by a group of academics from Bangladesh University of Engineering and Technology (BUET) and Loughborough University in UK shows that light shelves reduce overall indoor illumination when sky is overcast.
Figure 17: Light Shelves and Louvers Controlling Amount of Lighting Within the Building
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Additional Features: The light shelves installed in the National Library of Singapore features louvers. These louvers serve 2 important features to the building, wind and vegetation.
Diagram 14: Louvers on the Light Shelves Firstly, it helps to buffer the wind speed . Being the tallest building around Bugis area, the library is likely to face the strongest wind. With these louvers, the building is able to optimize the flow of wind and natural ventilation within the building. As the vegetation are planted on the balconies a t high levels, the wind would have destroyed the plants without the louvers acting as buffers.
Diagram 15: Process of Wind Buffering
Figure 18: Louvered Light Shelves at the Plaza
Secondly, these louvers serve as a balance between shading and penetration of sunlight for the vegetation around the library. The sky gardens and terraces with their veg etation on the balconies rely heavily on the light shelves as it requires the necessary sunlight yet in ne ed of the shading it provides to grow healthy.
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6.4.2 Passive Design Feature - Thermal Chimney
Situated in the city, it is expected that the thermal conditions are likely to be hot and stuffy. For the design of the library, the application of natural ventilation is heavily emphasized. Natural ventilation is able to move the air, whether to bring in fresh air or to remove stale air without the usage of any mechanics.
Figure 19: The Atrium in the Library Functions as a Thermal Chimney Natural ventilation mainly relies on pressure to move the air particles. When correctly applied, it functions well to give sufficient ventilation continuously without the need of any supervision. A unique feature of the National Library Building is the usage of a thermal chimney to induce thorough ventilation throughout the entire building. The decision to include a thermal chimney in the form of a 100m tall atrium topped with a skylight functions not only as a space for even air flow, but also as a path for light to enter. Much precaution has been placed for ventilating openings of the building. It was done orientating the horizontal openings away from the main streets to prevent polluted air from entering the building. At the same time, these openings that link to the atrium were averted away from East and West to keep hot wind from getting into the building.
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Figure 20: Atrium Viewed from Ground Level The atrium is the heart of the building and travels a vertical distance of over 16 storeys with openings on both ends. This gives ample space for air buoyancy to take place because the longer the vertical distance the more it allows a more even separation of cold air and warm air. The main function of the atrium is to flush out warm air in the building and bring cool air into the space of the building.
Figure 21: Inside View of the Atrium The principle of the thermal chimney uses air convection for stack ventilation. It moves the air using buoyancy where air of a higher temperature and higher pressure moves towards an area of lower temperature and pressure. Warm air rises and cool air sinks in the atrium, thus the warm and stuffy air is flushed out from the upper openings whereas cold air is drawn downwards and accumulates at the plaza. Visitors are cooled down before they enter the library from the plaza.
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Diagram 16: Stack Ventilation Occurs In the Thermal Chimney This order ensures that the building is constantly ventilated by the means of its structure. This is a green and cost efficient way of ventilation that the library had exploited to good use. Furthermore, stack ventilation as a form of natural ventilation has the ability to function without the presence of wind. The constant presence of temperature and pressure is sufficient to conduct the ventilation. The thermal chimney also becomes a visual linkage of the floors in the building, thus enhances the spatial experience in the library.
Figure 22: Openings Linking the Exterior to the Thermal Chimney On the contrary, it is possible possi ble that the usage of natural ventilation with openings that lead outside the building lowers the acoustic factor of the building. The library does have a substitution to this flaw which is by adding vegetation throughout the building to enhance noise absorption. Wide openings also prove to be harder for the control of air compounds as polluted air has a higher probability to enter the building.
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Additional Features: Additional feature of the thermal chimney is how it includes wind driven ventilation in its system. Also known as cross ventilation, wind driven ventilation creates pressure in its presence against an obstacle. The wind then forces its way toward a region with opposing pressure and the process repeats throughout the whole building. In the National Library Building, the windward façade forms the obstacle where strong wind create s pressure upon. On the other hand, the leeward regions experience lower pressure, this phenomenon draws the wind towards it through the openings on the facades. The air rush enables strong wind to constantly ventilate the space.
Diagram 17: Composition of Stack and Cross Ventilation The conjoined spaces of the horizontal opening and the atrium create a fusion of stack and wind driven ventilation. The constant convection of air in the atrium which is perpendicularly fused to the horizontal spaces draws air in from the horizontal space, thus ventilation continues throughout the building without interruption even if it lacks the presence of wind. Evaporative cooling is a form of passive cooling for buildings. It requires the presence of cooling ponds, spray mist or vegetation to cool the atmosphere. Generally speaking, water is the main element concerned in this strategy.
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Figure 23: Presence of Vegetation Enhances Evapotranspiration for Better Air Quality The design that National Library Building want to incorporate was a bioclimatic one, as this proves to be a greener way to balance out the manmade form. Bioclimatic design takes into consideration climatic conditions and its effects on the occupants. In efforts of creating a bioclimatic design, vast amount of vegetation was allocated throughout the building. Vegetation was ideal in creating the right ambiance for aesthetic values as well as a natural element to prevent the occurrence of heat islands. Fourteen lush tropical gardens can be found throughout the entire building, consisting of carefully selected plants that are able to thrive in various conditions provided in the building. Apart from general functions such as shading and heat absorbent, the green landscape aids the ventilation of the building by ensuring cool and quality air enters the building. Landscape induces evaporative cooling through evapotranspiration, which is a combination of evaporation and transpiration of plants. Transpiration is a natural process that occurs in plants in order to keep them cool as well as to regulate water in the plant. In this process, water is evaporated out of the plant into the atmosphere. This cools the surrounding air significantly as warm air is mixed with the cool water particles. Serving as a multifunctional element, landscaping however requires constant maintenance, which involves the rooftop irrigation system and so on. Space and planters were also required fo r landscaping.
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7.0 Active Design Strategies As energy is considered by many to be the most important category becoming sustainable, which is why it’s the heaviest weighted of all the categories in LEED rating system. Energy efficient designs in many ways have direct linked to passive design principles and strategies. Therefore concept of Overall Thermal Transfer Value (OTTV) is developed in design of building envelope to achieve energy efficiency.
The diagram above is the calculation method of OTTV. The concept is based on the assumption that the envelope of a building is completely enclosed. It comprises of ETTV and RTTV. But as the Singapore National Library is a high rise building, it’s less likely to have much RTTV. Parameters which are affecting OTTV of a building are building design, climatic, and local. Building design will be building orientation, envelope color and so on; climatic would have solar radiation, wind speeds, humidity and the others; while as the local focuses in the indoor comfort conditions. Which is the reason why differences of indoor and outdoor temperatures, the solar factor and the equivalent temperature difference are important (the datas which we had to research on previously), cause all these affects the value of OTTV in LEED system. Therefore, active design strategies are strategies that use equipment to modify the state of the building, create energy and comfort, for examples, fans, lights, pumps etc, which helps to improve the OTTV, especially for the local local parameters. The are the simulated devices which are used in the Singapore National Library: - Daylight sensors that are used together with automatic blinds at the building facades are found throughout the building to maximize its energy efficiency by monitoring the amount of natural light entering the building. - Public toilets installed with motion sensors. - Energy efficient lightings that are switched on only when required after closure of the library. - Use of rain sensors as part of the automatic irrigation system for landscaped areas. - Water efficient taps and cisterns are also used to conserve water.
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- Night setback for air-conditioning system in the library spaces after library operation hours with automated chiller controls. - Energy monitoring via BMS (Building Management System). - All escalator features motion sensors. - Chiller which removes heat from a liquid via water vapour compression or absorption refrigeration cycle. The liquid then can be circulated through a heat exchanger to cool air. - Mechanical thermal controller. - Localized intelligent switching for the office floor provide afterhours lighting only when required at the occupied space. - Variable volume and carbon monoxide sensors which maintaining acceptable conditions in all areas, and also to minimize the cooling of unnecessary volumes of fresh air. - Automatic blinds.
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8.0 Conclusion Upon receiving this task, we were psyched to be able to select the National Library of Singapore as our site for project 1 of Building Science 1. We were especially enraptured to visit the library because it holds the title of a platinum-graded building by the Green Mark Award and holds many innovative green features within the building. Our site visit took place as we visited Singapore somewhere around April. We contacted the librarian before heading to the library while we were still in Malaysia, and apparently a book written solely for the National Library was available in the library itself. Apart from the resourceful book we found on site, we made sure we visited the library both in the morning and the night in order to collect a more accurate data analysis. By doing so, we managed to gather quite a number of useful info and photos for the report and also admire the building in every angle. Many of the passive design features were instantly identifiable by us too such as the enormous light shelves and strategically positioned gardens. In short, we were glad to be able to work on a report for such an architecture glory, the National Library of Singapore. Through completing this report, we learned not just the passive design strategies, but also to analyse and land our opinions on improvements or alternatives. With proper guidance from our tutors Mr Bruce Lee and Mr Prince, we also learned to compile our findings and analytical data efficiently.
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9.0 References Book: Charles J. Kibert (2012). Sustainable Construction: Green Building Design and Deliv ery . New Jersey: John Wiley & Sons. Yoke Kiew (2008). Redifining The Library: The National Library of Singapore . Sinapore: GK Consultancy Ptd Ltd. Sara Hart (2011). EcoArchitecture the work of Ken Yeang. West Sussex: John Wiley & Sons. Jason P. (2013). The Skycourt and Skygarden: Greening the urban habitat . USA: Routledge. Peter James R., Howard R., Howard W. Dick (2009). The City in Southeast Asia: Patterns, Processes and Policy. Singapore: NUS Press. Peter H., Stephanus S. (2009). S. (2009). Constructing Identity in Contemporary Architecture: Case Studies from the South. Berlin: LIT Verlag Münster. Peter D. (2009). D. (2009). Engineering for a Finite Planet: Sustainable Solutions. London: Buro Happold (Firm). Redefining the library: the National Library of Singapore Shahin Vassigh, Jason Vassigh, Jason R. Chandler (2001). Building Systems Integration for Enhanced Environmental Performance. USA: J. Ross Publishing Yeang K., Lillian W. (2010). Dictionary of Ecodesign: An Illustrated Reference . USA: Routledge. Yeang K. (1999). The Green Skyscaper: the basis for designing sustainable intensive buildings . The University of Michigan: Prestel.
Website: Ajmalahammed K. (Aug 11, 2001). Passive Solar Design. Retrieved from http://www.slideshare.net/ajmalahammedkp/passive-design2. Average Weather for Changi, Singapore. (n.d.). Retrieved from http://weatherspark.com/averages/34049/Changi-Singapore. D. Tunas. (October 8, 2012) Maximizing Daylight Penetration with Light Shelves. Retrieved from http://greenasiaforce.com/Blog/maximizing-daylight-penetration-with-light-shelves/ L. Sadmin. ( January 9, 2012). National Library Board Singapore. Retrieved from http://lightingsolutions.sg/?p=1043 Passive Cooling. (n.d.). Retrieved from http://sustainabilityworkshop http://sustainabilityworkshop.autodesk.com/buildings/passi .autodesk.com/buildings/passivevecooling-and-ventilation-0
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