GREEN BUILDING INDEX – MS1525 Applying MS1525:2007 Code of Practice on Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings
Ar Chan Seong Aun. M Arch (Distinction), B Arch (Hons), B Bdg Sc (VUW, NZ), APAM, AIPDM, TAM.
Pertubuhan Arkitek Malaysia CPD Seminar 14th February 2009
1. FACTORS AFFECTING ENERGY USE IN BUILDINGS 1.1 Overview of Factors Affecting Energy Use in Buildings 1.2 Building Energy Indices 1.3 End Use & Actual Energy Consumption 1.4 Non Design Factors affecting Energy use in Buildings 1.5 Passive Design Factors affecting Energy use in Buildings 2. COMPLYING TO MS 1525 PASSIVE DESIGN ELEMENTS 2.1 Background to MS 1525 : 2007 2.2 Basics of MS 1525 : 2007 2.3 Building envelope, window design and OTTV 2.4 Roof Construction and RTTV 3. REFERENCES
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1. FACTORS AFFECTING ENERGY USE IN BUILDINGS 1.1 Overview of Factors Affecting Energy Use in Buildings The factors affecting energy use in buildings can be categorized into two groupings END –USE : Air Conditioning & Space Heating Lighting Power & Process FACTORS : Occupancy & Management Indoor Environmental Quality Climate Building Design & Construction Mechanical & Electrical Equipment 1.2 Building Energy Indices Before going into details of the factors affecting energy use, some method of comparing energy use - the energy use indices – will be explained. The index selected would depend on the intended application of the index and the normalizing factor. Among Architects the normalizing factor for comparing buildings is the gross floor area. The most commonly used index for comparing energy use in buildings is therefore the Building Energy Use Index BEI. This is usually expressed as kWh/m2/year which measure the total energy used in a building for one year in kilowatts hours divided by the gross floor area of the building in square meters. 1.3 End Use & Actual Energy Consumption The amount of energy used in buildings depends firstly on WHAT IT IS USED FOR. Thus the initial and most important step in isolating the factors affecting energy use is to determine its end-use. To architects, the category of use or building type will be the first factor to consider. Therefore to compare the energy index of say an office building which operates from 9 am to 5 pm to say a data processing center which operates computers around the clock would not be a reasonable comparison because the operating hours are different and the computers in the data processing centre would consume more electricity and may require a higher environmental standard. Comparing two schools in the same climatic region and similar operating conditions would however give a comparison of the energy performance of the two buildings. The energy audits carried out by Pusat Tenaga Malaysia, PTM , of Office buildings in Malaysia revealed that the majority of Malaysian Office buildings had BEI in the range of 200 to 250 kWh/m2/yr. Similar results were found in Singapore, with very few buildings
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A 2006 study of Household Energy use by CETDEM – Center for Enviroment, Technology & Development, Malaysia - headed by Ir Gurmit Singh in cooperation with Majlis Bandaraya Petaling Jaya and funded by Exxon Mobil found the following. Average Home Electricity Consumption Lighting 7% Entertainment 4%
Others 4%
Washing Machine 2% Cooking 5%
Cooling 45%
Heating 11%
Refrigerator 22%
Air conditioning and the refrigerator take up nearly 70% of the average household electricity consumption and air conditioning is the largest consumer of electricity in the home. With the threat of “Global Warming” and increasing energy cost, keeping the home cool will become Page 3
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increasingly important in the future. More interesting is the findings by CETDEM that close to 75% of a household’s energy consumption in the survey is in the form of petrol for getting to work and non-work related petrol consumption, as shown in the chart below. The planning of our future townships and cities, the spread of densities, the location of essential amenities and the layout of the major public transport routes to more efficiently and better serve the communities will become critical issues that will determine the quality of our future communities. Average Household Energy Consumption
Refrigerator 4.24%
Cooking 0.98%
Washing Machine 0.49%
Heating 2.18%
Cooling 8.73% Entertainment 0.83%
Fuel (others) 30.98%
Lighting 1.41%
Others 0.89% Gas (Kitchen) 5.66% Fuel (during work) 19.19%
Fuel (to/from work) 24.44%
1.4 Non Design Factors affecting Energy Use in Buildings. From the results of my own studies on energy use in New Zealand Schools, the following were found to have a significant impact on energy consumption in buildings. Occupancy and Management - It should be emphasized that people use energy. The building itself does not use much energy. We cool or heat the people in the building, not the building. There are four broad aspects to consider. 1. intensity of building occupancy 2. activity type 3. user attitude and behavior 4. management and organization First, the amount of energy used will generally be directly proportionate to the intensity of building occupancy. An office building rented out for only half a year will obviously use half the energy of an equivalent building occupied throughout the year. Operating hours will be another normalizing factor energy auditors must keep track of
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Second, the level of physical activity, the clothing worn, the duration of occupancy and age, size and background of the occupant will also affect the cooling / heating requirement. These factors will affect cooling requirements by influencing the preferred air temperature. Fanger and Kowakzewski’s work show for example that a person wearing light clothes and doing light desk work seated will feel comfortable at 25 degrees centigrade while he will only feel comfortable at 21 degrees centigrade with a light business suit. This 4 degrees difference can mean a 100% difference in the air conditioning energy requirement of a room. Third, the attitude of the occupants towards energy use has significant consequences. They are influenced by the aims and goals of the uses, the penalties and benefits to the user of conserving energy, expectations of the user and weather the users are aware of the relationship of their actions to the amount of air conditioning of heating energy used Finally, the organization and management of the building and its air conditioning equipment I terms of operation and maintenance will reflect on its efficiency and thus the energy used. Indoor Environmental Quality – The amount of air conditioning load required and thus air conditioning energy used depends very much on the air temperature maintained in the building. Some office buildings and hotels maintain indoor temperatures as low as 18 to 20 degrees centigrade when the comfortable temperature is about 24 degrees centigrade. There are many office buildings in Malaysia where the indoor temperature is so low that the occupants wear sweaters at the work desk. It is obvious the owners are no aware of the cost implications of their actions. It should also be noted that the average outdoor air temperature in Malaysia is only about 4 degrees above the comfort range. Climate – The number of publications and studies of the relationship of climate to architecture, people and energy use is very extensive. The purpose here is only to list some of the variables of concern. Climate affects the energy consumption in a building primarily by influencing the space cooling and heating requirements. The main climatic variables influencing the amount of energy needed for air conditioning are. 1. Solar radiation 2. Outside air temperature 3. Wind and rain 4. Night sky radiation Geiger has an extensive study of the physical variable influencing the microclimate. This would be useful for those planning large scale developments. The table below lists the major physical factors influencing the climate, some of which may be within the Designers control. MACRO CLIMATE Latitude Altitude
Solar Gain
Temperature Wind
Major Minor
Major Major
Minor
MICRO CLIMATE Page 5
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Terrain - Slope Ground Cover - Vegetation City / Country – Shading / Shelter Water Body – Inland / Seaside
Minor Minor
Minor Minor Minor Minor
Major Major Minor Minor
Site Planning & Microclimate The following topographic factors have been found by Geiger (3) to influence the microclimate around a building, and ultimately its cooling energy requirement. 1. 2. 3. 4. 5.
Altitude Terrain Water Body Natural Cover Cities
ALTITUDE – Temperature in the atmosphere decreases with increasing altitude by approximately 1 degree centigrade per 180 meters in the tropics and summer in the temperate regions and 1 degree centigrade per 220 meters in winter conditions TERRAIN – Cool air is heavier than warm air, and at night the outgoing radiation causes a cool air layer to form near the ground surface. The cool air behaves somewhat like water, flowing towards the lowest point. This “flow of cool air” causes “cool island” or “cool air puddles” to form in valleys. Accordingly, elevations that impede the flow of air effect the distribution of nocturnal temperatures by dam action and concave terrain formations become cool-air lakes at night. The same phenomenon is enlarged when a large volume of cool air flow is involved, as in valleys. The plateaus, valley walls and bottom surfaces cool off at night. Air flow occurs towards the valley floor. On the valley slopes, a series of small circulations mix with the neighboring warm air, causing intermediate temperature conditions. Accordingly, the temperature at the plateaus will be cool, at the valley floors very cool, but the high sides of the slopes will remain warm. This area often indicated by the difference in vegetation, is referred to as the warm air slope (thermal belt). WATER BODY – Water having a higher specific heat than land, is normally warmer in winter and cooler in summer and usually cooler in during the day and warmer at night, than land. Accordingly, the proximity of bodies of water moderates extreme temperature variations and lowers the peak temperatures in our tropical climate. In the diurnal temperature variations, when the land is warmer than the water, low cool air moves over the land to replace the updraft. During the day, such offshore breeze may have a cooling effect of about 5 degree centigrade. At night the direction is reversed. The effects depend on the size of the water body and are more effective along the lee side. NATURAL COVER – The natural cover of the terrain tends to moderate temperatures and stabilize conditions through the reflective qualities of various surfaces.
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Plan and grassy cover reduce temperatures by absorption of insulation, and cool by evaporation. It is generally found that temperatures over grassy surfaces are 5 to 7 centigrade degrees cooler than those of exposed soil. Other vegetation may further reduce high temperatures; temperatures under a tree at midday can be 3 degrees centigrade lower than in the unshaded environment. Conversely, man-made surfaces tend to elevate temperatures, as the materials used are usually absorptive in character. Asphalt surfaces can reach 51 deg.C in 37 deg.C air temperatures. The measurements taken by Professor Wong Nyuk Hien of the National University of Singapore shows the extent of the effect plantings have on the urban surface temperatures. The results of his case studies are quoted below.
This shows that plants play an important role in reducing thermal heat gain due to their sunshading effects during the daytime. For most plants, negative heat flux was found not only at night but also during the period when the solar radiation were not very strong during daytime. That is, the shading effects of plants is so good that they don’t just reduce heat from entering buildings but actually resulting in heat loss from the building.
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Plants contribute to creating better outdoor thermal environment and mitigating the Urban Heat Island effect. The ambient air temperatures were also measured at different heights above the hard surface and the vegetation part respectively on the rooftop of the commercial building. The ‘cooling effect’ of plants could be found from afternoon to sunrise next day. The maximum temperature difference was 4.2ºC, measured at 300mm height, around 1800 h. This shows that plants on rooftop gardens can reduce ambient temperature by as much as 4 ºC. Foliage of plants affects temperature readings. Under dense shrubs, surface temperature remains stable, with less than 3 ºC daily variations. The maximum surface temperature was only 26.5 ºC. The direct thermal effects of plants were further evaluated by measuring the heat flux through different types of roofs as shown in the diagram below. The heat flux was for hard surface, bare soil (without any plants), turf, tree, and shrub respectively.
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CITIES – Cities tend to be warmer than the surrounding countryside. That cities differ from the countryside not only in their temperatures but also in many other aspects of climate is widely recognized. The city itself is the cause of these differences. Five basic influences set a city’s climate apart from that of the rural area. First, there is the difference in surface materials. The predominantly rocklike materials of the city’s buildings and streets can conduct heat about three times as fast as it is conducted by wet sandy soil. This means that the city’s materials can accept more heat in less time, so that at the end of a day the rock like material have stored more heat than an equal volume of soil. Secondly, the city’s structure have a greater variety of shapes and orientations and function like amaze of reflectors, absorbing some of the solar radiation and directing much of the rest to other absorbing surfaces, so that almost the entire surface of a city absorbs and stores heat. In forest and open areas on the other hand, the heat tends to be stored in the upper part of plants. Since air is heated almost entirely by contact with warmer surfaces rather than by direct radiation, a city is more efficient in using sunlight to heat large volumes of air. Third, the city is a prodigious generator of heat. Among these are factories, cars and people. A study of Manhattan by Griffiths (4) suggested that the heat produced by combustion alone is 2.5 times greater than the solar heat gain Fourth, the city has a higher run-off of rain water. In the country, rain water remains on the surface or immediately below it. The water is thus available for evaporation, which is of course a cooling process. Because there is less opportunity for evaporation in the city, it loses less heat. Finally, the city air has a heavy load of solid, liquid and gas contaminants. These tend to reflect sunlight, reducing the amount of heat reaching the surfaces, but they also retard the outflow of heat resulting in higher peak temperatures.
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1.5 Passive Design Factors affecting Energy use in Buildings The building layout, planning, design, shape, fabric and construction cover a wide number of variables that affect building energy requirements. This the area where the basic decisions of the architect will have the most influence on the building’s energy use. How much then does the designer have? The following sets of estimates by Givoni should serve to illustrate a building’s influence on its indoor environment and thus air conditioning or heating requirement. Depending on the design 1. the indoor air temperature amplitude – swing from lowest to highest – can vary from 10% to 150% of outdoor amplitude 2. the indoor maximum air temperature can vary by -10 to +10 deg.C from outdoor maximum 3. indoor minimum air temperature can vary by 0 to +7 deg.C from outdoor minimum 4. indoor surface temperature can vary by +8 to +30 deg.C from outdoor maximum and minimum. The building related factors influencing energy requirements are numerous and complex. They can be classified under the following headings. 1. Size and Shape 2. Orientation 3. Roof System 4. Planning and Organization 5. Thermo physical properties – thermal resistance & thermal capacity 6. Window systems 7. Construction detailing. Size and Shape – Generally, a larger building will require more energy to cool than a smaller building because of the larger of space to be cooled. This is widely accepted. The question of whether a building needs less energy per unit volume or floor area is however a more complex one and still not completely resolved. Many theoretical researchers take the view that larger buildings need less energy per unit size because of their smaller surface area per unit size and thus lower heat gain per unit size. Based on this theory they say “ The larger a building, and the nearer to spherical in shape, the less are its energy needs because of the simple reduction in the ration of surface area to volume”. They conclude that “The architectural fad for angular protrusions of buildings is an energy wasting form”. The Building Research Unit however found from field data that compact buildings cost more to erect and had higher energy running costs than sprawling ones. These empirical findings were contrary to the Unit’s theoretical predictions. They concluded that the quality of “compactness” in layout is one which cannot, on present evidence, be shown to be of paramount importance. Stein reach conclusions similar to the BPRU “ …the maximum volume, minimum perimeter building will not be the most energy conservative and because of the mechanical systems required to provide interior comfort conditions at all times, may not even be the least expensive.” Building Orientation – Building orientation affects the air conditioning / heating energy requirements in two respects by its regulation of then influence of two distinct climatic factors.
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1. Solar radiation and its heating effects on walls and rooms facing different directions 2. Ventilation effects associated with the relation between the direction of the prevailing winds and the orientation of the building. Of the two, solar influence on energy is the most significant in the tropics and is extensively covered by many others. The table below compares the approximate daily solar gain for some typical Malaysian housing types. SOLAR HEAT GAINS IN TYPICAL MALAYSIAN HOUSING Single Storey Terrace Gross Floor Area Unit Floor Area Volume Roof Area Wall Area Envelope Area Roof/Envelope Area Wall/Envelope Area
Double Storey Terrace
Five Storey Flats
Eight Storey Apartments
880 880 14,080 1,012 484 1,496 68% 32%
1,408 1,408 18,304 792 968 1,760 45% 55%
60,500 750 665,500 12,100 28,050 40,150 30% 70%
81,680 850 898,480 10,210 47,872 58,082 18% 82%
North-South Fronting Roof Solar Gains NS-Wall Solar Gains EW-Wall Solar Gains Total Solar Gains-kWh/day Total Solar Gains-kWh/m2
30 5 0 35 0.04
24 10 0 33 0.02
363 198 165 726 0.01
306 356 246 908 0.01
East-West Fronting Roof Solar Gains NS-Wall Solar Gains EW-Wall Solar Gains Total Solar Gains-kWh/day Total Solar Gains-kWh/m2 Increased Solar Gain Percent
30 0 10 40 0.46 14%
24 0 19 43 0.31 29%
363 83 396 842 0.14 16%
306 123 711 1,141 0.14 26%
For an intermediate single storey terraced houses, where the roof makes up nearly 70% of the building envelope exposed to the sun, roof insulation becomes all important to keep the home cool. Orientation has less of an effect the difference in solar radiation for a north-south and east-west facing being only about 14% An intermediate double storey terrace house however has significantly more wall area and orientation will have a significant effect on the solar gain, being nearly 30% more for an eastwest facing house. For flats and apartments, depending on the aspect ratio and height of the building, an east west facing building can have 16% to 40% more solar gain than a north-south facing block. Page 11
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What can the Architect do to reduce this solar heat gain? The following are some suggested ideas. 1. Orientate the largest wall areas in the north-south direction 2. Locate service areas such as staircases, store rooms and service ducts in the east-west external walls. 3. Place as many service rooms on the roof top of flats as possible to reduce the solar gain through the roof. 4. Sky lights should not be used. If roof ventilation is required, use a jack up roof facing the north. 5. Shade east-west facing walls with large roof overhangs or plant shading trees in front of them. Roof System The typical Malaysian terraced house receives most of its solar heat gain from the roof. This is because the horizontal surface receives the highest solar radiation, peaking at about 350 Wh/m2 at mid-day in the tropical sun and it continues to receive the highest solar radiation level throughout the day. Add to that the higher ratio of roof to building envelope area; the typical roof receives from 50% to 85% of the total solar radiation as shown in the table below. SOLAR HEAT GAINS IN TYPICAL MALAYSIAN HOUSING
880 68% 32%
Double Storey Terrace 1,408 45% 55%
Five Storey Flats 60,500 30% 70%
Eight Storey Apartments 81,680 18% 82%
30 35 86%
24 33 71%
363 726 50%
306 908 34%
30 40 76%
24 43 55%
363 842 43%
306 1,141 27%
Single Storey Terrace Gross Floor Area Roof/Envelope Area Wall/Envelope Area North-South Fronting Roof Solar Gains-kWh/day Total Solar Gains-kWh/day Roof/Total Solar Gains East-West Fronting Roof Solar Gains-kWh/day Total Solar Gains-kWh/day Roof/Total Solar Gains
Reducing the solar heat gain through the roof should therefore be the first priority for keeping the home cool. Measurements by “Lafarge Roofing� have found peak temperatures differences between a roof insulated and an not insulated to be as much as 4.5 deg.C
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For sloping roofs the following if implemented correctly can reduce inside temperatures by as much as 4 degrees centigrade. 1. Use lighter coloured roofing or better still slightly reflective type roofing. 2. Apply aluminium foil insulation under the roof tile to reduce radiant heat gained by the roofing from being radiated to the ceiling. 3. Ventilate the loft area above the ceiling and below the roof tiles. Measurements taken in this loft area have been found to go as high as 45 deg.C for outside air temperature of 35 deg.C for not insulated roofs. 4. Apply a layer of rock wool insulation immediately above the ceiling to prevent the heat from the loft area fro being radiated and conducted into the living area immediately below the ceiling. Planning & Layout – It is not possible to generalize or quantify the complex implications that planning and layout of spaces will have on air conditioning and lighting requirements. Some areas where the layout will influence are listed below. 1. Grouping of spaces 2. Interaction of spaces 3. Ceiling height and space volume 4. Buffer zones Thermo Physical Properties – The properties of materials which affect the rate of heat transfer in and out of a building, and consequently the air conditioning or heating energy requirements are. 1. Thermal Resistance 2. Surface Convective coefficient 3. Absorptivity, Reflectivity and Emissivity 4. Heat Capacity Page 13
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Window Systems – The size, location, shape and orientation of glazed areas in a building will have a critical effect on both the heat gains and solar gains of a building because glazed areas have the highest hat gain per unit area and the major proportion of solar gains are also through windows. The importance of this factor is indicated by Stein’s finds that the school with the highest energy use per square foot in New York City was a completely sealed building with windowless classrooms. The amount of heat gins will also be influenced by 1. Type and design of shading system employed 2. Composition and type of glass 3. Obstruction and shading by surrounding buildings, structures and trees For tropical climates, external shading devices or recessed windows have been found to be the most effective method of reducing solar heat gains through windows without losing the significant benefits of day lighting. The recommendations by Assoc Prof Dr Ku Azhar Ku Hassan of University Science Malaysia should serve as a useful guide to Architects.
1. Horizontal shading devices is generally effective against high sun at both east and west orientations 2. Vertical shading is generally effective for south orientations 3. Egg-crate shading devices is the generally effective for all the orientations Construction Detailing – This will influence air conditioning loads in the following areas. 1. Infiltration cold air losses at junctions of different materials especially between roof joist and exterior walls, similar to the effect of leaving the door open in an air conditioned room 2. Conduction bridges – These are paths through which heat gain will be greatest, for example through a metal deck roof on a steel roof truss directly into the top floor of air conditioned spaces.
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Summary 1. The amount of energy used in buildings depends on WHAT IT IS USED FOR 2. Data on the actual energy consumption in Malaysian Office Buildings audited by PTM show that typical Malaysia Office Building consumes about 250 kWh/m2/year of energy of which about 64% is for air conditioning, 12% lighting and 24% general equipment. 3. The major non design factors influencing energy use in buildings are 1. Occupancy & Management, 2. Environmental Standards, 3. Climate 4. Major building related factors influencing energy requirements can be classified under the following headings. 1. Size and Shape 2. Orientation 3. Planning and Organization 4. Thermo physical properties â&#x20AC;&#x201C; thermal resistance & thermal capacity 5. Window systems 6. Construction detailing. 5. When amended, the UBBL will require air conditioned buildings Non-residential buildings larger than 4,000 square meters in floor area to have OTTV not more than 50 W/m2 6. Site surrounded with proper landscaping and water bodies can reduce the microclimate temperate from between 4 to 7 deg.C 7. Roof top gardens with shrubs can reduce the heat flux through the roof by more than 10 times compared with bare concrete roofs. 8. North and South oriented walls receive between 100 to 130 wh/m2 of solar radiation compared to 300 Wh/m2 for east and west facing walls. Depending on the building type and shape, a north-south oriented building can receive approximately 15% to 30% less solar gain than an east-west oriented building. 9. Locate low occupancy rooms on the west side of the home such as store and staircases. 10. The roof is the surface which receives the highest amount of solar radiation through the day. Insulating the roof is therefore vital in reducing air conditioning load. Peak temperatures can be reduced by 5 to 7 deg.C 11. Aerated lightweight concrete blocks have thermal resistance 3 times better than common sand cement blocks <1 w/m2K compared to >3w/m2K 12. Design Windows to block out direct sunlight. Let in the air and daylight. Diffused daylight gives more lumens per watt of heat produced than fluorescent lights. 13. External shading devices are more effective than internal blinds. 14. Horizontal shading devices are generally more effective against the noon sun at eastwest orientations 15. Vertical shading is only effective for south facing windows 16. Egg-crate and pineapple-skin type shading devices is the most effective type of window shading device and is suitable for all orientations
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2. COMPLYING TO MS1525 : 2007 PASSIVE DESIGN ELEMENTS 2.1
Background to MS 1525 : 2007
In March 2005, Kementerian Tenaga, Air dan Kommunakasi – KTAK – had proposed to the Ministry of Housing and Local Government – KPKT - that the Uniform Building By-Law (UBBL) be amended requiring that the building envelope design of NEW air-conditioned NON-RESIDENTIAL buildings to meet requirements of MS1525 with regards to OTTV, daylight, RTTV. This new by-law has been scheduled to come into force in 2007. What is MS1525 and what is OTTV? MS1525:2001 is the “Code of Practice on Energy Efficiency and Use of Renewable Energy for Non-residential Buildings.” MS1525 has recommended that the OTTV or “Overall Thermal Transfer Value” of a building should not exceed 50 W/m2. This is an index reflecting the thermal efficiency of a building. The higher the OTTV, the lower its thermal efficiency and hotter is the building during the day. A single storey office block with a metal deck roof without any insulation, for example, would not comply with this standard. What then is the role of the Architect and Engineer in this? As outlined in Section 1, the Size and Shape of the building, its Orientation, Planning and Organization, its Thermo physical properties – thermal resistance & thermal capacity, its Window systems and its Construction detailing among others will all affect its OTTV. Under the amended UBBL, Architects and Engineers will be required to compute the OTTV using the indices provided in MS1525 and submit these to the relevant approving Local Authorities, ensuring that they comply with the 50W/m2 benchmark, when they submit their building plans for approval. When fully implemented, this will bring in an era of more energy efficient buildings in Malaysia which will consume not only less electricity for air conditioning but will also be cooler. 2.2
Basics of MS 1525 : 2007
What are the basic requirements of MS 1525? • Architects and Engineers are required to comply with MS 1525 requirements for NON-RESIDENTIAL buildings with AIR CONDITIONED AREAS LARGER THAN 4000 SM after the UBBL amendment is made. • New Office Buildings, Commercial Complexes, Government Buildings, Hotels with more than about 50 rooms, Hospitals with more than about 50 beds, Institutional buildings, High Tech Factories Colleges and Universities, among others. • Normal shop-offices, non-air conditioned factories and warehouses, will not be covered under this standard. • Architects will have to submit OTTV & RTTV calculations to show compliance with Section 5 of MS 1525 • Engineers will have to ensure compliance with sections 6,7,8 and 9 of MS 1525
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Section 5.8 of the standard outlines the submission procedure. The following information shall be provided by a professional Engineer or Professional Architect: a) a drawing showing the cross-sections of typical parts of the roof construction, giving details of the type and thickness of basic construction materials, insulation and air space; b) the U-value of the roof assembly; c) the OTTV calculation; and d) the RTTV of the roof assembly, if provided with skylights.
2.3
Building Envelope, window design & OTTV
Heat conduction through the overall building envelope can be computed by calculating its overall thermal transfer value (OTTV). The OTTV requirement is aimed at achieving the design of adequately insulated building envelope so as to cut down external heat gain and hence reduce the cooling load of the air-conditioning system. The OTTV concept takes into consideration the three basic elements of heat gain through the external envelope of a building, as follows. 1. heat conduction through opaque walls 2. heat conduction through glass windows 3. solar radiation through glass windows The overall OTTV can be computed by the following formula outlined below extracted from the standard. 5.2.1 The OTTV of building envelope is given by the formula below: OTTV =
Ao1 x OTTV1 + Ao 2 x OTTV2 ...... x Aon x OTTVn Ao1 + Ao 2 ...... + Aon
..…
(1)
where, Aoi
is the gross exterior wall area for orientation i; and
0TTVi is the OTTV value for orientation i from equation (2). 5.2.2 For a fenestration at a given orientation, the formula is given as below: OTTVi = 15 α (1 − WWR) Uw + 6 (WWR) Uf + (194 x CF x WWR x SC)
…...
(2)
Where, WWR is the window-to-gross exterior wall area ratio for the orientation under consideration;
α Page 17
is the solar absorptivity of the opaque wall; GBI_MS1525_Chan SA/18/10/2008
Uw
is the thermal transmittance of opaque wall (W/m2 K);
Uf
is the thermal transmittance of fenestration system (W/m2 K);
CF
is the solar correction factor; as in Table 1; and
SC
is the shading coefficient of the fenestration system.
Although the mathematical formula may look very intimidating to many architects, we must try to remember that these methods were developed back in the mid 1980â&#x20AC;&#x2122;s and meant for calculating using only calculators. With the latest computer spread sheets, testing of different options would be a simple matter of extracting data from manufactureâ&#x20AC;&#x2122;s catalogues and imputing the basic data in the U-values spread sheets and then transferring them to the OTTV spreadsheets. What can Architects do to improve the OTTV of their building envelope and to comply with MS 1525? The following will serve as a useful guide. 1. Heat conduction through opaque walls, the first part of the formula in section 5.22 typically accounts for between 0.5 % to 5% of the overall OTTV. This will have a bigger impact if the window areas are small, such as in shopping complexes 2. Heat conduction through windows typically accounts for 10% to 20% of the overall OTTV, depending on the amount of glazing and if they are single or double glazed. 3. Solar radiation through glass windows is the greatest contributor to the OTTV typically accounting for between 70% to 85% of the overall OTTV, depending on the glazing area. The large constant of 194 already hints that this is a major factor in the overall OTTV. In order to keep the OTTV contribution for exceeding 50 w/m2, the shading coefficient is a major contributor to the overall OTTV as it can change this component by between 30% to 80% of OTTV. 4. Architects must however keep in mind not to use too much tinted glazing in order to bring up the SC, as section 5.4.2 requires that the daylight transmittance be more than 50%.
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2.4
Roof Construction & RTTV
Roof insulation is one of the most important and lowest cost strategies for energy efficiency as most of the solar radiation on a building is on its roof surface. • • • •
The roof plane receives the most Solar Radiation and for the longest period through the day >75% of the Solar Gain by a typical Intermediate Single Storey Terraced House is through its ROOF >50% of the Solar Gain by a typical Intermediate Double Storey Terraced House is through its ROOF >40% of the Solar Gain by a typical 5 Storey Bock of Flats is through its ROOF
MS1515 requirements for roof insulation are as outlined below. 5.5.1 The roof of a conditioned space shall not have a thermal transmittance (U-value) greater than that tabulated in Table 9. Table 9. Maximum U-value for roof (W/m²K) Roof Weight
Maximum U-Value (W/m²K)
Group Light
0.4
(Under 50 kg/m²) Heavy
0.6
(Above 50 kg/m²)
5.5.2 If more than one type of roof is used, the average thermal transmittance for the gross area of the roof shall be determined from:
Ur =
(Ar 1 U r 1 )
x (Ar 2 x U r 2 )...... + (Arn x U rn ) Ar 1 + Ar 2 ...... + Arn
…...
(4) where, Ur
is the average thermal transmittance of the gross area (W/m2 K);
U r1
is the respective thermal transmittance of different roof sections (W/m2 K); and
A ri
is the respective area of different roof sections (m²).
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The average weight of the roof is calculated as follows: Wr =
Ar 1 x Wr 1 + Ar 2 x Wr 2 ..... + Arn x Wrn Art + Ar 2 ..... + Arn
…..
(5) where, Wr
is the average weight of roof (kg/m2);
Ari
is the respective area of different roof sections (m²); and
Wra
is the respective weight of different roof sections (kg/m2).
5.5.3 If the roof area is shaded from direct solar radiation by ventilated external shading devices such as a double ventilated roof, the U-value may be increased by 50 %. 5.5.4 If external roof surface reflective treatments are used where the solar reflectivity is equal to or greater than 0.7 and the treated surface is free from algae growth, the U-value may be increased by 50 %. 5.6
Roofs with skylights
5.6.1
Concept of roof thermal transfer value (RTTV)
In the case of an air-conditioned building, the concept of Roof Thermal Transfer Value (RTTV) is applied if the roof is provided with skylight and the entire enclosure below is fully air-conditioned. 5.6.2 For roofs with skylight, in addition to the requirement of 5.5.1 the maximum recommended RTTV is 25 W/m2. 5.6.3
The RTTV of roof is given by the following equation. RTTV =
(Ar x U r + TDeq ) + (As x U s x ∆T) + ( A s x SC x SF) Ao
…..
(6) where, RTTV is the roof thermal transfer value (W/m2); Ar Ur
is the opaque roof area (m2); is the thermal transmittance of opaque roof area (W/m2 K);
TDeq is the equivalent temperature difference (K), as from Table 10; As Page 20
is the skylight area (m2); GBI_MS1525_Chan SA/18/10/2008
is the thermal transmittance of skylight area (W/m2);
Us
â&#x2C6;&#x2020;T is the temperature difference between exterior and interior design conditions (5 K); SC
is the shading coefficient of skylight;
SF
is the solar factor (W/m2), see 5.6.5; and
Ao
is the gross roof area (m2) where Ao = Ar + As.
As with the OTTV, the roof thermal transmittance or the RTTV, where there are skylights, can also be calculated using a simple spreadsheet. For light weight roof its 0.4 w/m2K and for heavy roofs its 0.6 w/m2K. What types of construction will comply and which will not? 1. Standard concrete tiled roofs with no insulation would not comply to the standard as the U-value would typically be about 0.7 w/m2K, exceeding the requirement of 0.4 w/m2K 2. Concrete tiled roofs with 50 mm fiberglass insulation would just barely meet the requirement, and 75 mm is therefore recommended. 3. A 100mm thick concrete roof slab with 3 w/m2Kwould not meet the requirement of 0.6 w/m2K and therefore an insulation of a minimum of 50 mm of polystyrene is required to bring it to about 0.5 w/m2K. A 100 mm is therefore recommended. Summary 1. Architects and Engineers are required to comply with MS 1525 requirements for NON-RESIDENTIAL buildings with AIR CONDITIONED AREAS LARGER THAN 4000 SM after the UBBL amendment is made. 2. Architects will have to submit OTTV & RTTV calculations to show compliance with Section 5 of MS 1525 3. With the latest computer spread sheets, testing of different options would be a simple matter of extracting data from manufactureâ&#x20AC;&#x2122;s catalogues and imputing the basic data in the U-values spread sheets and then transferring them to the OTTV spreadsheets. 4. Solar radiation through glass windows is the greatest contributor to the OTTV typically accounting for between 70% to 85% of the overall OTTV, depending on the glazing area. The large constant of 194 already hints that this is a major factor in the overall OTTV. In order to keep the OTTV contribution for exceeding 50 w/m2, the shading coefficient is a major contributor to the overall OTTV as it can change this component by between 30% to 80% of OTTV.
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3. REFERENCES 1. Fanger P.O “Thermal Comfort” McGraw-Hill, NY 1972 2. KowakzewskiJ.J “Thermal Comfort in Buildings”. A short course in Architectural Psychology, Department of Architecture, University of Sydney, Sydney, Australia 1974. 3. Geiger, Rudolf. “The Climate Near the Ground”. Harvard University Press, Cambridge, Massachusetts 1965 4. Givoni, B “Man, Climate & Architecture”. Elsevier London 1969. 5. Building Performance Research Unit “ BUILDING PERFORMANCE”. Applied Science Publishers Ltd, London. 1972 6. Stein R G “Architecture & Energy. Conserving Energy through Rational Design” Anchor Press / Doubleday, Garden City, New York. 1977 7. Baird, Donn, Pool, Brander & Chan. “Energy Performance of Buildings” CRC Press Inc 1984. USA. 8. Chan Seong Aun “Low Energy School Design. A Study of Factors Affecting Energy Use in New Zealand Primary Schools” Master of Architecture Thesis, Victoria University of Wellington, New Zealand. November 1983. 9. “Capacity Building in the Energy Commission (ST) on EE / DSM “ Inception Workshop PWTC 7th June 2002 10. “MS 1525 : 2007 Code of Practice on Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings” Department of Standards Malaysia. 11. Prof. Lee Siew Eng National University of Singapore. “Energy Efficiency in Singapore: Current Status and successes and Future Prospects”. Paper at National Seminar on Low Energy Offices, Pan Pacific Hotel, Kuala Lumpur 8th & 9th October 2001 12. “MECM LEO SEMINAR Advances on Energy Efficiency and Sustainability in Buildings” Palace of Golden Horses Kuala Lumpur 21-22 January 2003. 13. Deepa Sammy, Steve Lojutin, Tang CK, Poul Kristensen “Design Strategies for New Buildings (Non-Domestic)” KTKM, JKR, DANIDA, April 2004 14. “Making Malaysian Homes Energy Efficient – Stakeholder Workshop organized by CETDEM” Impiana Hotel Kuala Lumpur 12 June 2004 15. Ku Azhar Ku Hassan Assoc Prof Dr.(USM) “Tropical Building Design : The effectiveness of Solar Shading Devices” . National Seminar on Built Enviroment 5-6 Aug 2002, Kuala Lumpur. 16. Wong Nyuk Hien , Chen Yu and others. “Handbook on Skyrise Greening in Singapore” Centre for Total Building Performance, School of Design & Environment, National University of Singapore and National Parks Board, Singapore. 17. CETDAM “Working with the Community on Energy Eficiency at Household Level in Petaling Jaya” A CETDAM Study on Energy Efficiency 2006 .
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2/10/2009
GREEN BUILDING INDEX â&#x20AC;&#x201C; MS1525 PAM CPD SEMINAR ON MS1525:2007 Code of Practice on Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings 14th February 2009 PAM Kuala Lumpur
Ar Chan Seong Aun M Arch (Distinction), B Arch (Hons), B Bdg Sc (VUW, NZ), APAM, AIPDM, TAM
CONTENT 1. WHY BE ENERGY EFFICIENT? 2. ENERGY EFFICIENT ARCHITECTURE 3. BASICS OF MS1525 SECTION 5 BUILDING ENVELOPE 4. COMPLYING WITH MS1525 OTTV & RTTV 5. SAMPLE BUILDING MS1525 CALCULATION
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WHY BE ENERGY EFFICIENT?
â&#x20AC;˘ The skill and vision of those who shape our cities and homes is vital to achieving sustainable solutions to the many environmental, economic and social problems we face on a local, national and global scale
Peter Graham
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Energy Efficient and Sustainable Buildings Why ? To reduce the pressure on our environment and our resources To give our children and grandchildren a (prosperous) future Because buildings that cannot be rated Environmentally Friendly will loose out in the property market of the future.
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As Responsible Architects we have to go for a more sustainable form of Architecture
ENERGY EFFICIENT ARCHITECTURE
KEY PASSIVE DESIGN FACTORS AFFECTING ENERGY USE IN BUILDINGS FOR ARCHITECTS TO CONSIDER
SITE PLANNING & MICRO-CLIMATE ORIENTATION SIZE & SHAPE PLANNING & ORGANIZATION THERMAL RESISTANCE THRMAL CAPACITY WINDOW SYSTEMS CONSTRUCTION DETAILING
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SITE PLANNING & LANDSCAPING
•Landscaped surroundings can reduce the outside ambient temperatures by as much as 7 deg C •Peak surface temperatures of bare concrete can be as much as 25 deg C higher than surface temperatures of grassed over areas. • The key point is to reduce the outside temperature by improving the surroundings as much as possible.
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∆
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T = 39 – 25 = 14°C
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SITE PLANNING & MICRO-CLIMATE
∆
T = 32 – 25 = 7°C
Urban Heat Island Effect : Case Singapore
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ORIENTATION
â&#x20AC;˘ A double storey house facing east-west can expect to get nearly 30% more solar radiation than an identical north south facing house â&#x20AC;˘ For flats and apartments, depending on the aspect ratio and height of the building, an east-west facing building can have 16% to 40% more solar gain than a northsouth facing block.
ORIENTATION
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ROOF INSULATION IS ONE OF THE MOST IMPORTANT DESIGN DECISIONS FOR ENERGY EFFICIENT BUILDINGS
• The roof plane receives the most Solar Radiation and for the longest period through the day • >75% of the Solar Gain by a typical Intermediate Single Storey Terraced House is through its ROOF • >50% of the Solar Gain by a typical Intermediate Double Storey Terraced House is through its ROOF • >40% of the Solar Gain by a typical 5 Storey Bock of Flats is through its ROOF
THERMAL INSULATION FLAT ROOFS
Use 50-100 mm thick insulation 50mm - 100mm Insulation
100mm Cast Concrete 900mm Ceiling Air Space
Interior Air-Conditioned Space
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12mm Ceiling Tiles
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DOUBLE ROOF WITH SERVICES AT ROOF TOP
INSULATED DOUBLE ROOF
THERMAL INSULATION PITCHED ROOFS
Add 100mm thick insulation & ventilate the roof Metal Deck Roof 50mm ventilation gap 100mm Insulation Wool
35°C
Aluminum Sheet
45°C
Roof Space
Ceiling Tiles (fiber board)
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THERMAL INSULATION PITCHED ROOFS
Add 100mm thick insulation to the ceiling for retrofit
Metal Deck Roof Existing 50mm Insulation Wool
35°C 45°C
Aluminum Sheet
Roof Space Additional 100mm Insulation on the Ceiling to prevent heat from affecting the space below.
Ceiling Tiles (fiber board)
Source : Dr Nigel / Lafarge
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Roof Garden IBP Atrium Singapore
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THERMAL INSULATION FOR WALLS
• Avoid Sandbrick – Very poor U-value > 3 W/m2K
Plaster Plaster
• Insulated Walls
115mm
– Aerated Lightweight Concrete (ALC) • U-value of 1 W/m2K for 100mm
Brick
• Use U-value < 1 W/m2K – 150 mm thick ALC
15mm
15mm
Typical U-value of 2.43 W/m2K
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Source : CSR
Source : CSR
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WINDOW SHADING • External Shading Devices are more effective than Internal Blinds. • Only need to block out Direct Sunlight.
HORIZONTAL LOUVERS FOR N-S FACING WINDOWS
VERTICAL LOUVERS FOR E-W FACING WINDOWS
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AFTER AIR CONDITIONING LIGHTING ENERGY CONSUMPTIONB IS THE NEXT MOST IMPORTANT FOR COMMERCIAL BUILDINGS. Energy Index 150.0 worst
130.0
base mewc
kWh/m2/year
110.0 90.0 70.0 50.0 30.0 10.0
Fresh Air Gain
Dehumid Fresh Air
Dehumid Ppl Latent Gain
Ppl Gain
Ext Conduction Gain
Solar Gain
Small Power Gain
Lighting Gain
Chiller Energy
Lighting
Small Power
-30.0
Fan Energy
-10.0
WINDOWS & DAYLIGHTING IN BUILDINGS
• Daylight in Building offset electrical lighting load • Electrical lights produces more heat than Diffused Daylight • Zone electrical lighting system correctly
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DAYLIGHTING ESSENTIALS 1. Bring the light in high, above the view plane 2. Diffuse sunlight inside the space. Don’t allow beam sunlight to strike work surfaces. 3. Use only north and south vertical windows 4. Choose the glazing carefully.
•Continuous strip of narrow windows up high •A few view windows. These have a low visible transmittance (0.2 – 0.3), to balance the luminance of the walls with the luminance of the outdoor view. Every work place in the building should have a visual connection to the outside •Eggshell white color in the upper part of the room to bounce the light across the room •Mid-to-light colors in the lower part of the room
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CHOOSE SPECTRALLY SELECTIVE GLAZING
ideal window transmittance
solar spectrum
0
500
1000
1500 Wavelength,
2000
2500
3000
nm
visible
BASICS OF MS1525
SECTION 5 : BUILDING ENVELOPE
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• MS 1525 COMPLIANCE TO BE INCORPORATED IN UBBL REVISION BY KPKT • ARCHITECTS & ENGINEERS REQUIRED TO COMPLY TO MS1525 FOR NON-RESIDENTIAL BUILDINGS WITH AIR CONDITIONED AREAS LARGER THAN 4000 SM AFTER UBBL AMENDMENT • ARCHITECTS / ENGINEERS WILL HAVE TO SUBMIT OTTV & RTTV CALCULATIONS TO COMPLY WITH SECTION 5 OF MS1525 • ENGINEERS WILL HAVE TO ENSURE COMPLIANCE WITH SECTION 6,7,8,AND 9
Temperature and Humidity
( Subang Weather Data) Why do we need to air condition our Offices? Relative Humidity 80%
The Comfort Zone
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5.8 Submission procedure The following information shall be provided by a professional Engineer or Professional Architect: a)a drawing showing the cross-sections of typical parts of the roof construction, giving details of the type and thickness of basic construction materials, insulation and air space; b)the U-value of the roof assembly; c)the OTTV calculation; and d)the RTTV of the roof assembly, if provided with skylights.
5.2.1
The OTTV of building envelope is given by the formula below:
OTTV =
where, Aoi 0TTVi
A o1 x OTTV 1 + A o 2 x OTTV 2 ...... x A o n x OTTV n A o1 + A o 2 ...... + A o n
is the gross exterior wall area for orientation i; and is the OTTV value for orientation i from equation (2).
5.2.2 For a fenestration at a given orientation, the formula is given as below:
OTTVi = 15 Îą (1 â&#x2C6;&#x2019; WWR) U w + 6 (WWR) U f + (194 x CF x WWR x SC)
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OTTVi = 15α(1-WWR)Uw + 6(WWR)Uf + 194xCFxWWRxSC Heat Conduction through Walls
Heat Conduction through Windows
Solar Heat Gain through Windows
OTTV < 50 W/m2
HEAT CONDUCTION THROUGH WALLS
15α(1-WWR)Uw 15 x Solar Absorb x Wall Area x U-value of wall (Heat Conduct through Wall) α = Solar Absorption = Colour of walls Depending on WWR this is typically 0.5% to 5 % of Total OTTV for high rise buildings
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Black Paint
0.90-0.99
White Paint
0.15-0.30
Aluminium Oxide Paint
0.09
Red Roof Tiles
0.4-0.8
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U-VALUE OF WALLS
U-value is the heat transmission value of the wall in W/m2K U-values have to be worked out from the Thermal Resistance of the respective materials making up the wall The Overall thermal resistance of the composite wall = Thickness x Conductivity x Resistance of each component totaled up The Higher the Thermal Resistance, the lower the UValue and therefore the Thermal Transmittance of heat through the walls
HEAT CONDUCTION THROUGH WINDOWS
6(WWR)Uf 6 x Window Area x U-value of Window (Heat Conduct through Window) Depending on WWR this is between 10% to 20% of Total OTTV for high rise buildings
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WINDOW TYPE
TYPICAL U-VALUES w/m2K
Single Glazed window
5.7
Single Glazed Window Low-E
4.2
Double Glazed Window
2.6-2.9
Double Glazed Window Low-E
1.2
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SOLAR GAIN THROUGH WINDOWS
194xCFxWWRxSC 194 x Correction Factor (Depend on Orientation-Table 4) x Window Area x Shading Coefficient (Table 5,6 & 7) Depending on WWR this is between 75% to 85% of Total OTTV. The large constant of 194 already hints that this is a major factor in the OTTV SC can be a major contributor to reducing the Overall OTTV as it can change this component by between 30% to 80%
COMPLYING WITH MS1525 OTTV & RTTV VALUES
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U-VALUE OF ROOFS
U-value is the heat transmission value of the Roof in W/m2K U-values have to be worked out from the Thermal Resistance of the respective materials making up the Roof The Overall thermal resistance of the composite Roof = Thickness x Conductivity x Resistance of each component totaled up The Higher the Thermal Resistance, the lower the UValue and therefore the Thermal Transmittance of heat through the Roof
Table 9. Maximum U-value for roof (W/m²K)
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Roof Weight Group
Maximum U-Value (W/m²K)
Light (Under 50 kg/m²)
0.4
Heavy (Above 50 kg/m²)
0.6
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MS 1525 ROOF INSULATION REQUIREMENTS a)
a drawing showing the cross-sections of typical parts of the roof construction, giving details of the type and thickness of basic construction materials, insulation and air space;
b)
the U-value of the roof assembly;
•
Concrete tiled roofs (Light weight) with NO INSULATION will have a U-value of 0.7 w/m2K
•
With 50mm fiberglass, the U-value will be about 0.35 w/m2K
•
100mm Concrete roof slab (Heavy weight) will have a U-value of 3 w/m2K
•
With 50mm polystyrene foam, the U-value can be brought down to 0.56 w/m2
REDUCING SOLAR GAIN THROUGH WINDOWS
194xCFxWWRxSC 194 x Correction Factor (Depend on Orientation-Table 4) x Window Area x Shading Coefficient (Table 5,6 & 7) Depending on WWR this is between 75% to 85% of Total OTTV. The large constant of 194 already hints that this is a major factor in the OTTV SC can be a major contributor to reducing the Overall OTTV as it can change this component by between 30% to 80%
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IMPROVING THE SHADING COFFECIENT OF WINDOWS
Window SC = Glass SC x Shading Device SC SC = 0.6 x 0.8 = 0.48 a reduction of more than 50% window
Projection
Window Height
R1 = Projection / Window Height Typical = 0.3m/1.2m = 0.25 SC = 0.8
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TABLE 5 HORIZONTAL PROJECTION SHADING COFFICIENTS 0.9 0.8 0.7 Shading Coefficient
0.6 0.5 0.4 0.3 0.2 0.1 0
0.3 to 0.4
0.5 to 0.7
0.8 to 1.2
1.3 to 2.0
North/South
0.77
0.71
0.67
0.65
East
0.77
0.68
0.6
0.55
West
0.79
0.71
0.65
0.61
NE/SW
0.77
0.69
0.63
0.6
NW/SE
0.79
0.72
0.66
0.63
R1 (Projection / Window Height)
Projection
0.3m Window Height 0.9m
R1 = Projection / Window Height Top = 0.3m/0.3m = 1.0 SC = 0.67
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TABLE 6 VERTICAL PROJECTIONS SHADING COEFFICIENTS 1 0.9 0.8 Shading Coefficients
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
0.3 to 0.4
0.5 to 0.7
0.8 to 0.12
North/South
0.82
0.77
0.73
1.3 to 2.0 0.7
East
0.87
0.82
0.78
0.75
West
0.86
0.81
0.77
0.74
NE/SW
0.83
0.77
0.72
0.69
NW/SE
0.84
0.79
0.74
0.71
R2 (Projection / Window Width)
TABLE 7 EGG CRATE SHADING COFFICIENTS 0.9 0.8
Shading Coefficients
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
R1=1 R1=1.2R1=1 R1=1 R1=0.2 R1=0.2 R1=0.4 R1=0.4 R1=0.4 R1=0.6 R1=0.6 R1=0.8 R1=0.8 R1=0.2 1.8 R2=0.4- R2=0.6- R2=0.2- R2=0.6- R2=1.4- R2=0.2- R2=0.8- R2=0.2- R2=0.8- R2=0.2- R2=0.6- R2=1.4R2=0.2 R2=0.21.8 1.2 0.4 1.8 0.6 1.8 0.6 1.8 1.2 0.4 0.8 0.6
North/South
0.71
0.62
0.56
0.59
0.49
0.46
0.52
0.43
0.5
0.4
0.51
0.41
0.38
0.38
East
0.77
0.69
0.62
0.63
0.54
0.5
0.54
0.44
0.49
0.39
0.48
0.39
0.35
0.33
West
0.77
0.69
0.61
0.64
0.54
0.51
0.56
0.46
0.52
0.42
0.52
0.42
0.38
0.38
NE/SW
0.73
0.63
0.55
0.6
0.48
0.44
0.51
0.39
0.47
0.36
0.48
0.36
0.32
0.32
NW/SE
0.75
0.66
0.58
0.63
0.52
0.48
0.55
0.44
0.52
0.41
0.52
0.42
0.38
0.38
R1=Projection/WindowHeight R2=Projection/WindowWidth
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WINDOW SHADING • External Shading Devices are more effective than Internal Blinds. • Only need to block out Direct Sunlight.
WINDOW EXTERNAL SHADING
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HORIZONTAL LOUVERS FOR N-S FACING WINDOWS
VERTICAL LOUVERS FOR E-W FACING WINDOWS
HORIZONTAL LOUVERS FOR N-S FACING WINDOWS
VERTICAL LOUVERS FOR E-W FACING WINDOWS
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WINDOW GLAZING
Spectrally Selective Glazing : Lets in the lights, blocks out the heat
Tinted Glazing Heat Light
Sp. Sel. Glazing Heat Light
Typical Values, Double Glazing : Light 60% Transmission Heat 30 % Transmission
GLASS SHADING COFFICIENTS & U-VALUES SHGC (Solar Heat GainCoffecient) TINTED
SOLAR CONTROL
U-value
Clear
COLOUR
0.7
0.54
0.58
U-value(With Eclad) 0.35
Grey
0.45
0.33
0.58
0.35
Bronze
0.5
0.38
0.58
0.35
Blue-Green
0.5
0.38
0.58
0.35
Artci Blue
0.4
0.3
0.58
0.35
Evergreen
0.39
0.29
0.58
0.35
U-value(With Eclad)
SC=SHGC/0.87 TINTED
SOLAR CONTROL
U-value
Clear
COLOUR
0.80
0.62
0.58
0.35
Grey
0.52
0.38
0.58
0.35
Bronze
0.57
0.44
0.58
0.35
Blue-Green
0.57
0.44
0.58
0.35
Artci Blue
0.46
0.34
0.58
0.35
Evergreen
0.45
0.33
0.58
0.35
Source : Pilkington
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SAMPLE BUILDING
MS1525 CALCULATION
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THANK YOU
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SUN-SHADING DESIGN METHODE FOR MULTY-STOREY OFFICE BUILDING IN JAKARTA AT PRELIMINARY DESIGN STAGE Dewi Larasati ZR Construction Management Laboratory Department of Architecture, Institute of Technology Bandung dewizr@ar.itb.ac.id
ABSTRACT The problem of controlling a built environment and creating conditions favourable to human activities (e.g. controlling the influence of climate) is as old as human civilization. Through the ages men have sought the shape of the building, to fulfil basic human needs, making a protection from the bad environment elements and provision of a favourable atmosphere. Building design has reflected, throughout its history, with the advanced solution in each period. In fact a lot of young designer in recent time do not understand enough about this problem nor trying to learn from the past. Therefore their design became environmentally unfriendly, or if they try to solve this problem, the solutions are expensive and inefficient. This research objective is to give a good understanding for young designer on building design using climatic approach (bioclimatic design concepts). Another objective is to provide design method to help them to achieve better solution on sun shading design as the implementation of bioclimatic design concepts. The final design solution is not result of a subjective trial and error process, but more as a systematic and detailed decision making process. The sun shading design method consists of three stages. The first is selecting alternatives from available alternatives. The second stage is determining energy consumed for air conditioner and lighting for each selected alternative. The last stage, before final design, is determining the construction, operational and maintenance cost for the implementation of sun shading. Key word: sun shading, design method, bioclimatic, energy, design criteria, design stage.
1. INTRODUCTION Most of multi-storey buildings in Jakarta have functions as offices which operate in day time with hot tropical climate (effective temperature in Jakarta approximately 300-330 C). In the office utility, air conditioning of room absolutely needed to reduce the temperature until seize the optimal comfortable (effective temperature for optimal comfortable approximately 220-260 C). This situation occurs because thermal condition can affect to the health and work productivity (Soegijanto and friends, 1998). Based on energy audit result in Jakarta by Energy Conservation Commission – a commission under Directorate General of Electricity and New Energy of Government of Indonesia, 1993, around 51% usage of buildings energy is used to operate air control system. In 1998, although the usage percentage for the air control system decrease until 38% (Purwoko, 1998), the number of electricity energy usage for that purpose is still high. The efforts to reduce the energy load have been done by blocking and filtering the sunlight inside the building. In this situation, one of the approximations which can be used is the bioclimatic concept in design. According to Ken Yeang (1996), Malaysian architect which introduce his works with “Bioclimatic Skyscrapers” term, there are two justifications in the bioclimatic design concept, occupant maximally comfortable, and the usage of energy minimally. The other way which can be implemented in the bioclimatic concept implementation is Sun Shading. The usage of sun shading in the multi-storey building give positive effects (as expected), and also enable the appearance of negative effects, in the comfortable and construction cost. The numbers of the positive and negative effects in the multi-storey building are different; depend on sun shading type and shape, building mass, building function, geographical position, building site condition, etc. In optimizing of sun shading at the building, in term of comfortable and reducing cost, need to develop a design method which implemented in design process.
2. SUN SHADING CLASSIFICATION AND CHARACTERISTIC ON MULTY-STOREY BUILDING Several types of sun shading design (Lam, 1986) which can be used in order to satisfy designing purpose can be recognized (Table 1). Those types can be grouped according to distinctive classification, based on couple of things which is connected with the sun shading performance. In the next development, those types can be enlarged by combination the basic shapes. The table below are sun shading basic shapes:
Transparent Overhang Solid Overhang
Louvered Overhang
Sun-catcher
Lightshelf
Reflectance Exterior Lightshelf
Mirror Sloped Lightshelf
Double Overhang
Reflectance Interior Lightshelf
Medium Scale Horisontal Louvers Multiple Louver Horizontal
Temporary Overhang- Awning
Precast Sloping Lightshelf
Dynamic Lightshelf
Medium Scale Dynamic Louvers Venetian Blinds
Medium-Scale Vertical Louvers
Smaller Scale Dynamic Louvers
Table.1. Sun shading Type Based on the types of sun shading above, sun shading can be classified as shown in the table below: No 1
2
3
Classification
Sun Shading Type
Based on layout position Horizontal Sun shading, can directly decide the position with the sun movement specification. Usually for the East-West of the building, fixed horizontal sun shading can be effectively used.
Solid Overhang, Louver Overhang, Sun-catcher, Transparent Overhang, Temporary Overhang, Temporary Awning, Double Overhang, Reflectance Exterior light shelf, Reflectance Interior Light shelf, Mirror Sloped Light shelf, Pre-cast Sloping Light shelf, Dynamic Light shelf & Sun-catcher, Big Scale- Multiple Horizontal louver, Medium Scale- Multiple Horizontal louver, Small Scale-Multiple Horizontal louver (Venetian Blinds).
Vertical Sun shading, controlling low sun-angle but frequently be the view blocker
Big Scale- Fixed Vertical Sun shading, Medium Scale -Vertical Louver fixed & Dynamic, Small Scale-Dynamic Vertical Louver.
Based on move ability Fixed Sun shading, The orientation cannot be adjusted
Almost all types of sun shading can be designed to fulfil this classification
Dynamic Sun shading, The orientation is adjustable
Louver Overhang, Sun catcher, Transparent Overhang, Temporary Overhang, Temporary Awning, Mirror Sloped lightshelf, Precast Sloping Lightshelf, Dynamic Lightshetf & Sun-catcher, Multiple Horizontal louver – medium scale, Multiple Horizontal louver – low scale (Venetian Blinds), and Dynamic Vertical Louver – medium scale and Dynamic Vertical Louver –low scale.
Base on physical shape Solid Sun shading Generally, good in covering from sun light entrance
All types of sun shading, except Louver.
Non-solid Sun shading The leak of light and heat is high frequently present
All types of Louver
4
Base on relationship with the structure Sun shading part of structural element
Solid Overhang, Sun-catcher, Double Overhang, and Multiple Louver Horizontal – large scale.
Non-Structural element Usually it’s not long life
All types of sun shading could be part of this category
Table 2. Sun Shading Classification
Some characteristics of sun shading based on classifications are shown below (all evaluations are held in Jakarta/ tropical area): 1. Sun Shading Characteristic Based on Comfortable Parameter Classification base Layout direction
Shading capacity
Shape
Classification detail
Characteristic
Characteristic base
Horizontal sun shading
Generally good to anticipate high sunangle, especially in the East-West direction
Vertical sun shading
Anticipate low sun-angle in the morning and evening (usually in the North-South direction)
Based on the sun shading placement direction with the ability of anticipating seasonal sun-angle (objective character).
Fixed
Anticipate daily sun-angle is not as good as dynamic sun shading
Dynamic
Very good in anticipating daily sunangle if it can be adjusted automatically
Solid
Able to block sun light, relevant to its dimension (good in glare control)
Non- Solid
Based on classification relation to ability anticipating daily sun-angle (objective character)
Usually is implemented to get reflected light
Relation to anticipate glare and the necessary of green area at the height (characteristic produced/ subjective)
Can be used as green area in higher place
Relation to maintenance (objective)
Cause to leak of unblocked sun light (less in glare control)
For non solid, based on scale, impact to view, interior and exterior, and composition & architectural proportion (subjective)
Large scale; generally, view is still free of sight and easier in maintenance Small scale; covering view and more difficult in maintenance rather than large scale
Table 3. Sun shading characteristic based on comfortable parameter (Note: Some of the subjective and objective characters must be measured specifically.)
2. Sun Shading Characteristic Based on Energy Consumption Classification base Based on the layout position of sun shading at the building
Classification detail East (E)
Characteristic
Characteristic base
Generally it’s good enough to reduce the energy usage (air control) because the amount of solar energy in the East side which blocked by the sun shading
West (W)
Generally it’s good enough to reduce the energy because the amount of energy loads in the West side which blocked by the sun shading
North (N)
Reduce the energy because of energy load caused by sun radiation in low angle in the morning
South (S)
Reduce the energy because of energy loads caused by sun radiation in low angle in the evening
East (E) – West (W)
It’s good enough to reduce the energy because high energy loads in the East-West is reduced (high sunangle)
North (N) – South (S)
Reduce the energy loads caused by sun radiation in low angle in the morning and evening
Whole sides
Good, because it reduce the sun radiation in the whole sides but require the highest investment cost
Connection with :
Energy load (for air control) caused by decision of placing the sun shading in certain position (need to calculate with the computer software)
Table 4. Sun shading characteristic based on energy consumption parameter
3. Sun Shading Characteristic Based on Construction Parameter Classification base Shading capacity
Relation to the structure
Possibility to use a type of material
Classification detail
Characteristic
Fixed
Long life duty cycle, operational & maintenance is easier
Dynamic
Operation & maintenance is harder
Part of structure
Rigid and long life duty cycle, in common; but limited in design (aesthetically)
Additional element
Not as strong as if part of structure, mainly in height, but flexible in design
Concrete
Cast in site or prefab system Constructability and maintenance depends on design, long life in common
Metal
Generally as additional element and the maintenance is harder than concrete
Others
Depend on another material that used
Characteristic base Relation to usage age and operation easiness (objective) Difficulty in maintenance and investment cost which must be spent (objective character) Has a close relevancy with structural strength, constructability and sun shading age
Relation to constructability, the age and maintenance cost (objective)
Table 5. Sun shading characteristic based on construction cost parameter
3. SUN-SHADING DESIGN METHOD FOR MULTY-STOREY OFFICE BUILDING AT PRELIMINARY DESIGN STAGE Sun shading is a building component (including multi-storey building), which one of the function is to make shading area to avoid the direct sun radiation to the building. In turns, the temperature inside the building will decrease, while thermal comfortable will increase. Sun shading design method at preliminary design stage is extended development from exterior wall design in the schematic design stage. Diagram 1a. and 1b. show the process when the sun shading design is at preliminary stage. Diagram 1a.
Site Planning
Concept: Block plan Accessibility + circulation Parking + paving
Concept: Cladding + Exterior wall Roof plan
Exterior Design
Interior Design
Space Program
Sun shading Design
Form Materials Position Lay-out
Notation: Input / Output
Data
Process
Diagram 1b.
Concept: Block plan Access + circulation Park + paving
Building Envelope Design
Material varieties and sizes
Door/window Design
Form Size Position
Notation: Data
Input / Output
Process
Diagram 1a,1b. Design process of sun shading at preliminary design stage. The diagram above shows the main things which are the basic approach in the design method compilation process. They are: 1. Input-output approach process with feedback is the main and continuously process in the developing method. 2. The function consideration to define the alternative is the first consideration to gain sun shading alternative types. 3. Technological consideration in the materials is also one of the design products which are expected in the process phase. 4. Comfortable and esthetical considerations are main considerations. 5. Cost consideration with techno economy is one of the products at the edge of the process.
Diagram 2
STAGE-I
To reduce alternative of sun shading based on location, function, and building type criteria (basic criteria is comfortable of thermal and visual)
To reduce alternative of sun shading (output STAGE-I) based on the counting of energy consumption (Computer Aided : DOE)
STAGE-II
Data base: • Performance of sun shading based on location, function and building types • Characteristic of layout, position, site planning, unit price of energy and construction • Comfortable value of psychological
Feedback If energy-saving is not satisfied (changing criteria)
Feedback If cost-saving is not satisfied
Cost counting of sun shading types (investment cost + energy) (Computer Software : WinEst+MS.Excel)
STAGE-III To count psychological comfortable value
Basic of decision making based on selected alternative
Notation: Data
Proces
Diagram 2. Stages of sun shading design process at preliminary design. Base on the process used in method which is developed above, we can conclude some points regarding the design as the following: o
Design that is conducted is sun shading design for multi-storey building in Jakarta that use bioclimatic design concept. That is why in the beginning stage of this design is to implement bioclimatic design concept base on design principles and bioclimatic design analysis i.e.: block plan, building orientation, etc. This approach must be implemented at the conceptual design stage and developed in schematic design.
o
Selection on alternative sun shading type, base on : data base from the study of sun shading on multi-storey office building in Jakarta, design requirement criteria, building function, site location, and multi-storey building requirement. From numerous sun shading types that available, we select the alternative sun shading type, consider there are different requirement in certain location with certain function. Beside sun shading type, we also determine the sun shading position placement and material uses.
o
Evaluation toward alternative choices is base on concept justification namely: comfortable and cost. Bioclimatic justification is used because the beginning concept of this design is bioclimatic design concept. Some of tools which are used to evaluate are DOE 2.I.E and building techno economic.
From few things that persistent with the design, it can be seen that the whole method that will be developed is in the “bioclimatic” frame. That is why the evaluation toward some alternative choices that have been chosen is base on bioclimatic design concept. Base on this concept there are three justifications in this evaluation i.e.: 1. Maximising user comfortable (as maximum as possible). 2. Minimizing the uses of energy/cost of energy (as minimum as possible) 3. Minimizing the uses of investment cost (as minimum as possible)
Generally, the stages of sun shading design method at preliminary design stage are as the following: o
The bioclimatic design concept is implemented in the beginning of design stage, and developed at the schematic design stage (such as building mass shape, mass orientation, dimension, etc base on literature study), which will become one of sun shading design input at the preliminary design stage.
o
Stage 1, to reduce alternative sun shading from available types by using design criteria requirement. The criteria which are used as the main consideration are: 1. Sub stage 1-a, building location (relate with climate that influence the building and easiness of implementation at location). 2. Sub stage 1-b, building function (relate with building activity and typology, such as office, hotel, housing, etc.). 3. Sub stage 1-c, building type (high, low or medium building). Alternative choices base on the available sun shading data base, in order to evaluate the performance that fit with criteria that has been determined.
o
Stage 2, evaluation toward sun shading energy uses. Before this stage, the sun shading position placement at the building is determined (sub stage 2-a) base on sun shading alternative input which had chosen previous (stage 1 input). This evaluation that base on bioclimatic justification namely the uses of energy as minimum as possible can be done manually or using computer software, e.g. DOE.2.I.E (sub stage 2-b).
o
Stage 3, determination of material uses and final evaluation toward alternative chosen, base on minimum cost justification and use maximum comfortable inside the building. This stage is divided into three sub stages as the following: 1. Sub stage 3-a : applying material uses, 2. Sub stage 3-b : cost calculation. (energy cost vs. construction cost), and 3. Sub stage 3-c : calculation on psychological comfortable resulted
4. SUMMARY OF SUN SHADING DESIGN METHOD AT PRELIMINARY DESIGN STAGE In order to observe the whole sun shading design method in a simple manner, the summary of the whole method is presented in tables that contain detail of each stage, including process and the input-output that is required in each process as the following: STAGE-1 STAGE
INPUT
PROCESS
OUTPUT
Output from previous stage (schematic design) Data from condition of location Data base of sun shading types Criteria of sun shading based on location Performance of sun shading on site
Decision for alternative of sun shading type-1
Alternatives-1 of sun shading type based on location
Stage 1-b
Evaluate the chosen alternative based on criteria of the function requirement (office building, commercial building, etc)
Alternatives-2 of sun shading type based on location and function
Stage 1-c
Output from Stage 1-b Condition of the building (multi storey) Criteria of sun shading based on building types Performance of sun shading on building types Implementation of sun shading on site
Evaluate the chosen alternative based on criteria of building type requirement (multi storey bld/ sky scrapes, wide span, etc.)
Alternatives-3 of sun shading type based on location, function and building type requirement (multi storey bld/ sky scrapes)
Stage 1-a
Output from Stage 1-a Building function and code Criteria of sun shading based on function Performance of sun shading on building function
To STAGE-2
STAGE-2 STAGE
INPUT
PROCESS
OUTPUT
Stage 2-a
Output from Stage 1-c Criteria of sun shading based on layout Previous data about site plan design (schematic design) Data of the need of shading area
Decision for position of sun shading
Alternatives-1 of sun shading at layout position
Stage 2-b
1.
Evaluate the chosen alternative based on energy-saving, e.g. using DOE v2.1E
Alternatives-2 of sun shading at layout position 2 Total of Energy (KW, W/m ) Dry and Wet temperature, total of sun radiation, wind speed, etc. Summary of room lighting load Summary of equipment load Summary of performance of building energy Electrical cost
2. 3. 4. 5.
6. 7.
Output from Stage 2-a Building code Output from schematic design : Site plan data (altitude, azimuth, timezone, humidity, building area, etc.) Construction data per space zone (wall, floor, ceiling, roof, window) Schedule of building usage (lighting, equipment usage, etc.) Dimension (exterior envelope, window, floor, sun shading, etc.) General condition of room (illumination level, maximum glare level permitted, temperature, lighting type, etc.) Condition of service area Description per room (based on zone)
STAGE-3 STAGE
INPUT
Stage 3-a
Output from Stage 2-b Possibility data of implemented materials
Determining implementation of material
Alternative of using material
Stage 3-b
Construction cost analysis of sun shading (using techno-economy)
Value of energy-cost saving Construction Cost of sun shading IRR (interest rate of return)
Output from Stage 3-a Construction data (Construction cost) Data of electrical energy cost Building data
PROCESS
OUTPUT
Computer aided : MS.Excel©, WinEst©, etc. Stage 3-c
Output from Stage 3-b Characteristic data of psychological comfortable Data of priority scale on site
Measuring of psychological comfortable value
Psychological comfortable value
Summary
Evaluation result within whole stages
Recommendation based on the counting result (on cost and energy)
Decision based on recommendation
5. SUGGESTIONS Some suggestions that are recommended from this study are: 1. The method that is developed in this research is the early study. We expect that it can be followed up in further studies. We also recommend to develop this method as a decision making process of design in a computer program. 2. Some points that need further observation are: A more complete data base arrangement with a better accuracy level in order to support the method which is developed. A more accurate criteria formulation in order to get a better solution design.
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To simulate the method in a computer program, it is better to use the latest version and comprehensive program (such as DOE, Win Est, Excel, etc.).
3. It is better to use evaluation technique with a good evaluation method in order to observe subjective data evaluation which has not been developed.
6. BIBLIOGRAPHY 1). --------------, 1993. Standard on Energy Conservation in New Building Design, ASHRAE 2). Asworth, Allan, 1994. Perencanaan Biaya Bangunan. Gramedia, Jakarta 3). Beckett, HE and Godfrey, JA, 1974. Windows, Performance, Design and Installation. Van Nostrand Reinhold Company, New York. 4). Birdsall, B.E, dkk, 1994. DOE-2 Basics, Version 2.IE.California, USA. 5). Daryanto, 1989. Suatu Kajian Tentang Pengendalian Energi Menggunakan Selubung Bangunan pada Beberapa Gedung Kantor Bertingkat Banyak di Jakarta. Program Arsitektur, Pasca Sarjana ITB, Bandung. 6). Departemen Pekerjaan Umum, 1993. Standar Tata Cara Perencanaan Konversi Energi pada Bangunan Gedung. Indonesia. 7). Egan, M. David, 1975. Concepts in Thermal Comfort. Prentice Hall, Inc., Englewood Cliffs, New Jersey. 8). Handler, Benjamin. A, 1970. System Approach to Architecture. American Elsevier Publishing Company, Inc, New York. 9). Haviland, David, 1994. The Architect Hand Book of professional Practice Vol 2. AIA, USA 10). Jones, Christopher, 1979. Design Method, Seed of Human Future. Willey Interscience, London. 11). Lam, William M.C, 1986. Sunlighting, As Formgiver for Architecture, Van Nostrand Reinhold Company, New York. 12). Larasati, Dewi, 2000. Metode Desain Sun Shading pada Tahap Prarencana Bangunan Tinggi. Thesis Riset, Program Arsitektur, Pasca Sarjana ITB, Bandung. 13). Meyer, William T, 1983. Energy Economic and Building Design. Mc Graw-Hill Book Company, New York. 14). Olgyay, Victor, 1967. Design with climate, Bioclimatic Approach to Architectural Regionalism, Princeton University Press, New Jersey. 15). Sugijanto, dkk, 1998. Rancangan Konstruksi Selubung Bangunan Ditinjau dari Aspek Konservasi Energi serta Lingkungan Thermal dan Visual pada Kondisi Iklim Tropis.Riset Unggulan Terpadu IV, FTI ITB. 16). Yeang, Ken, 1996,The Sky Scraper Bioclimatically Considered. Architectural Record, Academy Edition, Boston, USA.
Emphasis on Passive Design for Tropical High-rise Housing in Vietnam Le Thi Hong Na* and Jin-Ho Park**
* Inha University, Department of Architecture Korea, hongna2311@yahoo.com ** Inha University, Department of Architecture Korea, jinhopark@inha.ac.kr
Abstract: Passive design is a key element of sustainable building. It aims to maximize comfort for people living in a home while minimizing energy use and other impacts on the environment. This means making the most of free, natural sources of energy, such as the sun and the wind to provide heating, coo ling, ven tilation and lighting and t o con tribute to re sponsible ener gy us e. During recent years, high-rise apartments quickly developed in Vietnam’s urban areas. There is, however, a limitation of architectural design theory for high-rise buildings, especially those lacking passive design pri nciples. This st udy foc uses on the ba sic pr inciples o f pass ive de sign for hig h-rise housing in Vietnam in relation to the local climate. Firstly, the Vietnamese climatic conditions are presented. The n, the less ons le arned fr om t raditional ho using design i n Vietnam are ment ioned. Finally, a passive de sign m ethod of V ietnamese high-rise hous ing is in troduced base d on fi ve points i .e. i) configuration and orie ntation; ii) faç ade; iii) natura l ventilation; i v) dayl ighting; v) passive heating, cooling and thermal storage. Results of the study with potential recommendations for design principles in Vietnam are outlined. Key words: High-rise housing, Passive design, Local climate, Vietnamese architect.
1. Introduction Passive mode is designing for improved comfort conditions without the use of an y electromechanical systems. Examples of passive mode design strategies include adopting appropriate building configurations and orientation in rela tion t o t he loca lity’s c limate a nd suitable fa çade de sign. Pa ssive-mode des ign d oes n ot pre clude us ing mixed-mode or pr oductive mode devices, although, they s hould be the last option for creating optimal comfort levels inside the building. Passive mode requires an understanding of the climatic conditions of the locality, then designing not just to s ynchronize t he built form’s design c onsidering the m eteorological c onditions, bu t t o optimize t he am bient energy of the locality into the design with im proved i nternal c omfort c onditions. Furthermore, i f the design op timizes its pass ive mode, an impr oved l evel of com fort re mains duri ng an y electrical power failure [16]. Maximum utilization of natural resources such as solar energy, wind and daylight is t he most efficient way of saving en ergy. Th e so -called passive d esign is directly generating power t hrough utilization o f cl imatic characteristics but not in virtue of mechanical system. Properly designed and constructed passive buildings offer 3135
many benefits: low energy bills year-round; high economic return on the incremental investment on a life cycle cost basis a nd gre ater fina ncial i ndependence from future rises in ene rgy c osts; grea ter therm al comfort, less reliance on noisy me chanical sys tems; reduced building m aintenance costs r esulting from l ess re liance o n mechanical systems; increased daylighting or higher quality lighting systems which can increase environmental sanitation and health; reduced energy usage and reliance on fossil fuels [13]. The significance of passive design is very important for h igh-rise housing as it consumes mor e energy. Th is means t hat a rchitects an d des igners should comprehend and consider the environment, geography and climate during the design procedure. Thus, the design should adapt to cl imatic characteristics by means of thermal insulation, natural ventilation and sunlight shading. Along with the devel opment of i ndustry, com merce, fin ance and ra pid incre ase of urba n p opulation, lan d resources bec ame sc arce. As a re sult, the main cities of Vietnam, such as H anoi Ci ty and Ho C hi M inh C ity (HCMC) are in the process of transforming into the high-density, high-rise living and working environments. In this context, high-rise apartments are being quickly developed because of their gigantic economic value. During recent years, the ‘ international style’ with fully glazed facades has become a popular trend among Vietnamese architects. Meanwhile, international design teams are almost always insensitive to local climate conditions when designing buildings in Vietnam, often resulting in unnecessary discomfort and energy waste. Natural ventilation and illumination are not considered carefully but on an avera ge level. The core is usually c losed and located in the centre. In many cases, a solid form with a huge rectangle or a square is designed. There is no suitable method to prevent the evil influence on housing from direct solar radiation [4]. Additionally, there is absolutely no highrise building using sun energy nowadays. Although high-rise buildings can decrease the waste of land resources and return more land to nature, their ne gative impacts on the environment have become more and m ore serious due to consumption of a large amount of natural resources and energy. Passive design should become a national strategy regarding Vietnamese architecture to reduce building maintenance costs, to protect the environment and human health and to develop high-rise buildings in a sustainable way [3]. In this study the basic principles of passive design for the high-rise housing of Vietnam in relation to the local climate is investigated and the results with potential recommendations for design principles in Vietnam are outlined.
2. Local Climate of Vietnam Vietnam is loc ated in t he tropical and temperate zone, in the centre of South East Asia between the latitudes of 23.220 and 8.300 nort h, lyi ng i n the ea stern par t of the Indochina pe ninsula. It is cha racterized b y a stron g monsoon influence, a considerable amount of sunny days and with a high rate of rainfall and humidity. There is a difference i n clim atic para meters betw een the north and t he sou th of V ietnam. H anoi expe riences t he typ ical climate of nort hern Vietnam, w here summe rs a re hot a nd humid, and winters are relatively cool and dry. The summer months receive the majority of rainfall in the year (1,682 mm rainfall per year). The winter months are relatively dry, although spring then often brings light rains. Rains become more intense with the monsoons in the winter. The minimum winter temperatures can dip as low as 6– 70C not including the wind chill, while summer can ge t as ho t as 38– 400C. While HCM C e xperiences t he ty pical c limate o f southern Vietnam wh ich h as a tropical climate, with an average humidity of 75%. A year is divided into two distinct seasons. The rainy season, with an average rainfall of about 1,800mm annually (150 rainy days per year), begins in May and e nds in lat e November. The dry se ason lasts from December to April. The ave rage t emperature is 28 0C; the highest 3136
temperature so metimes rea ches 39 0C around noon in late A pril, w hile the lowest m ay fall below 160C i n t he early mornings of late December [12]. It can be stated that cooling is the dominant demand throughout the year in both Hanoi and HCMC, but a smaller amount of heating is required in Hanoi which amounts to about 20% of the occupied pe riod. Th e a mount of c ooling in degree hou rs (above 25 0C) in H CMC is almost do uble that of Hanoi. In both cities dehumidification is a significant demand [2].
3. Lessons from Vernacular Housing in the Traditional Vietnamese House Generally, a lo cality’s traditional b uildings of fer t he best e xamples o f appropriate passive-mode de sign or bioclimatic design. Learning from traditional examples, it is important to adopt a design strategy that begins with a design of the built form by optimizing all the passive-mode strategies appropriate to the climate and ecology of that locality. The basic design of the traditional house and its construction methods give it great flexibility so that extensions to the house can be carried out whenever necessary [15]. N
W
E b
a
c
Verandah
S
Indoor space
(a) (b) (c) Figure. 1 (a) Main part of folk house typical; (b) Cross ventilation through two air-holes in lengthwise section; (c) Ventilation in the cross section A distinctive feature of the typical Vietnamese house is that the main house’s shape always is rectangular along an east-west axis to reduce solar insolation on the wider sides of the building as shown in Figure 1(a). The roof, having a big slope with gables at both ends, is covered with a lightweight and excellent thermal insulator made from t hatch, which holds little heat during the day and cools do wn at night. The gab les are covered by eaves which provide protection from driving rain while allowing ventilation as shown in Figure 1(b). The doors and windows are made by bamboo or wood, lining the main facade and providing good ventilation and views for the house. This quality o f ope nness is a lso reflected by the lar ge open interior spac es with m inimal pa rtitions. Another dis tinctive fe ature is that l arge and de ep vera ndas, next t o t he forecourt, provide sun p rotection, splashing r ain preve ntion, channels for ven tilation, and bu ffer spac es betw een t he ou tdoor and i ndoor environment as show n in F igure 1(c) . A pond is often p ositioned in front of rural h ouses. Cl imbing p lants covering the surface of the house are used as a living and self-generating cladding system. Fruit-trees of short or medium height are located in front of the main façade while those which are higher and have bigger canopies are planted at the rear. These features help to channel cool breezes, to avoid cold winds, to provide shading from the sun and to increase natural ve ntilation. The “ground” floor is often sited at a hi gh l evel with insulation l ayers made by refined bricks. Houses on st ilts are common i n the highlands and mountainous areas. These fe atures help t he ho uses not t o con tact di rectly w ith the h umid g round. O ne of t he most con genial of the t raditional Vietnamese ho use i s its openness. The hou se is d ivided i nto a reas, rathe r t han rooms, for var ious socia l an d household activities. In the typical urban architecture of ancient cities, inner courtyards provide natural light and combine with corridor systems to promote natural ventilation. From a distance, the traditional Vietnamese house seems to merge naturally with the environment.
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4. Basic Principles of Passive Design for High-rise Housing in Vietnam Based on an understanding about typical climatic conditions and learning from traditional housing construction, together with studying about the t heory and the practice of passive method in the w orld, the ba sic principles of passive design for tropical high-rise housing in Vietnam is outlined in 5 points as follows.
4.1 Built-form Orientation and Configuration Built-form or ientation i s a si gnificant design c onsideration, mainly w ith re gard to solar ra diation and w ind. High-rise houses are more exposed than lower-rise houses to the full impacts of external temperatures, wind and sunlight and therefore their built form configuration, orientation, floor-plate shape and use of buffer components can have particularly important effects on energy-conservation design and natural lighting of the interior spaces. The sun light route way, in F igure 2(a ), d ecides the m ain orientation of hig h-rise housing that ensure s th e utilization of natural sunlight resources to process daylight, passive solar energy heating and solar electric power generation. The loc al wind direction as sho wn in Figure 2(b) and air flow distribution are also prerequisites for composition that avoid intercepting cold and moist air d uring the cold season and e ncouraging coolness during the hot season. According to Xu et. al.â&#x20AC;&#x2122;s approach, the most suitable orientation and composition that utilizes the potential of the nat ural climate i n the si te c an be ens ured t hrough a c areful s tudy on basic micro c limatic conditions. N
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(a) (b) Figure. 2 (a) Sun path in HCMC [3]; (b) Direction of the prevailing wind in Vietnam Making the b uilt form in the co nfiguration appropriate t o the su n p ath for that latitude ca n red uce ener gy consumption by as much as 30% to 40% at no extra cost. The classic design approach to orienting a building on its site is to l ocate t he l ong si de on a tru e e ast-west a xis to m inimize solar loa d on e ast and w est surface s, particularly during the hot season. Windows on the east and west surfaces are typically minimized to eliminate as much as possible the potential of high morning and afternoon solar loads. South-facing walls will experience a variable su n load d uring the day a nd w indows ar e ea sily protec ted from sol ar loads thr ough the use o f roof overhangs, shading devices, or recessing the windows [1]. It is generally held that the built form should have 1:2 to 1 :3 len gth rati os for climatic z ones li ke in V ietnam. A tropic al hi gh-rise house in V ietnam, if arra nged longitudinally from nort h t o south as show n in F igure 3(a) , has to be ar a n air -conditioning l oad t hat in unoptimized conditions (i.e. without special façade treatment for th e external walls) is 1.5 times that of a building arranged l ongitudinally from ea st to we st. To a rrange accord ing to pr iority, the orie ntations ens uring na tural ventilation for housing in Vietnam are south, east-south, east, west-south, west, west-north, north, and east-north [3]. G ood orie ntation i ncreases the e nergy efficiency of a hom e, ma king it m ore comfortable to l ive in and cheaper to run. 3138
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(a) (b) (c) Figure. 3 (a) Fitting orientation of the urban high-rise housing in Vietnam; (b) Service cores on the hot sides of built form; (c) Sun path and HCMC tower designed by Ken Yeang [17] Internal l ayouts sho uld be a dapted to c limate a nd bu ilding or ientation so tha t room s or space s w ith spe cific functions are locate d ad jacent to t he most appropriate facades [1 3]. The room s, whi ch are locate d ad jacent to direct nature, are according to priority the bedroom, family room, living room, kitchen, toilet and dinning room. Similarly, the orientations for open space in apartments are south, east-south, east, west-south, west, west-north, north and east-north [3]. The service cores can be positioned on the ‘hot’ east or w est sides of the bu ilding, or both a s show n in F igure 3(b), to serve as solar buffers in t he tropical zone . The d ouble-core confi guration is clearly the type providing a minimum air-conditioning load, in which the opening is from north to south and the core runs from east to west. Conversely, the core type characterized by maximum air-conditioning load is the central core configuration, in which the main daylighting opening lies in the southeast and northwest directions. A good example is H CMC tower design by Ken Yeang as shown in Figure 3(c). In this high-rise building, the west façade is shaded by long sky-terraces and the core is located in the west-north side.
4.2 Building Envelope A w ell-designed b uilding e nvelope w ill yi eld sig nificant e nergy sav ings. The build ing enve lope m ust c ontrol solar he at gain, con duction or dire ct heat transm ission, a nd i nfiltration or leaka ge he at transmission [1] . Compared w ith ordi nary b uildings, the building en velope of hi gh-rise buildings has its special characteristics. The important guidelines for building envelope design in Vietnam are recommened as follows: •
Wind sp eed and w ind pressure grow s qui ckly with the escalation of he ight tha t l eads t o qu ick hea t exchange between building enve lope an d outside. Th is si tuation is no t of be nefit to energy conservation. Furthermore, a high-rise house receives more sunshine than a low -rise house (including direct radiation, diffused radiation and radiation reflected from roof of the nearby multistory buildings). Thus, m aterials with h igh t hermal mass and e nough t hickness should be c hosen fo r the bu ilding envelope of high-rise housing to reduce and delay the impact on internal space cause by external wall temperature fluctuation [13].
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The ideal external wall should act as an environmentally responsive filter as shown in Figures 4(a) and 4(b). The envelope should have adjustable openings that operate as sieve-like filters with variable parts to provide na tural ven tilation, con trol cross-ventilation, provi de views to the o utside, give solar protection, regulate wind-swept rain and discharge heavy rain, provide insulation during cold season, meet demands of hot season, and promote a more direct relationship with the angle for both summer sun penetration and winter sun penetration, as these differ. The permeability of the skin of the building to light, heat and a ir and i ts visual trans parency m ust be controllable and capable of modification a s
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shown in Figure 4(c), so that t he bu ilding can rea ct t o cha nging lo cal clima tic conditions. These variables include solar screening, glare protection, temporary thermal protection and adjustable natural ventilation options [15]. Cross ventilation
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(a) (b) (c) (d) Figure. 4 (a) Vertical and cross ventilation model for the building envelope; (b) Horiziontal ventilation and vertical sun-screening on the South facade of the Moulmein Rise, Singapore; (c) Controllable window [5]; (d) Protruding balconies in the Newton Suites, Singapore. •
A useful device is t he use of r ecessed terraces or ‘sky-courts’ to serve as interstitial zones between the inside areas and the outside areas. Besides providing shading to that portion of the building, sky-courts can al so serv e t he following mu ltiple f unctions: a s eme rgency ev acuation (e xample in t he ev ent o f future incre ase in per missible p lot ra tio); or a s areas f or the futur e spa tial add ition of e xecutive washroom, kitchenettes, etc. They also furnish the built form’s users with a more humane environment as an optional o pen-to-the-sky zo ne for them to step ou t from the in ternally enc losed fl oor ar eas, to enable them to experience the external environment directly and to enjoy views as shown in Figure 4(d).
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The g reen approach ru ns contrary t o those façade designs t hat re ly on hermetically seal ed skins. The ‘green’ façade can reduce solar heat gain to the space through external shading devices, provide fresh air vent ilation, ser ve as an a coustic bar rier, give m aintenance ac cess and m ake a contribution to the building’s aesthetics.
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The designed system’s green roof should be considered as the building’s fifth façade [15]. The roof of a high-rise built form is less important thermally compared to that of the lower rise building type because of it s small surface area co mpared to th e ex tensive ext ernal wa ll a rea. Th e d irection of sol ar-heat absorption of the ro of o n the t opmost floors need s to be considered. In V ietnam, roofs should b e constructed of low t hermal capacity materials with reflective outside surfaces where there is no s hade. The roof should preferably be of double construction and provided with a reflective upper surface. Roof and terrace areas might also be vegetated.
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The external façade should be as light colored as possible to reduce the heat effect and to lighten overall air-conditioning loads. For Vietnamese housing, there is a necessity to prevent direct radiation mainly from the north-west, west and south-west [3].
4.3 Natural Ventilation Natural ventilation i ncludes a number of w ays in which ex ternal air and wind can be use d to bene fit th e occupants of buildings. Natural ventilation may be used for increasing comfort (air movement), for health (air
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change) or for building cooling (wind speed). It addresses two basic ne eds in buildings: the re moval of fo ul air and moisture and the enhancement of personal thermal comfort. Reasonable organization of na tural ventilation leads to ene rgy saving and cost cutting. The ene rgy consumption of t he natural ventilation is o nly half of usin g air-conditioning. Meanwhile, it dec reases dependency of those equipment which use by mechanical ventilation and air-conditioning to ensure a healthy building environment. Furthermore, it re duces the emission of carbon dioxide. High-rise housing has a much longer vertical distance and much bigger volume than that of the ordinary buildings. Thus t he or ganization of natural ventilation in h igh-rise housing is mor e difficult [13]. Some guidelines for natural ventilation in Vietnam are presented as follows: •
Conventional ty pes o f natural ve ntilation include w ind pr essure ventilation a nd thermal pre ssure ventilation. But s imply using these tw o types in h igh-rise housing are not s uitable because o f t he instability of natural wind and heat loss in the upper air. Mixed ventilation combined with an atrium are better ways to establish ventilation strategies in different seasons and use mechanical ventilation under extreme climatic conditions. Figure 5 prese nts natural ventilation strategies with an atrium in dif ferent seasons used in Commerz Bank Headquarters, Frankfurt, Germany that was designed by Norman Foster [13].
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(b) Figure. 5 Natural ventilation strategies in summer (a) and winter (b) in Commerz Bank Headquarters [13] •
For t he façade of high- rise housing, w ind performance grow s exponentially as i t move s upwards. Therefore, if natural ventilation i s used in the building, then a series of modified venting devices for different h eight zones i s n eeded. The e xternal f açade c an co nsist o f a s eries o f sy stems (e.g. d ouble façade-skin, flue-wall, etc.) depending on the desired thermal effect and venting system. A ‘fly roof’ can be used to shade the entire t opmost floors. It protects the core building from radiant h eat and allows cooling breezes to flow beneath it. A vertical and cr oss ventilation model for faç ade skin an d the roof are presented in Figure 4(a).
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A bui lding can be divided into the rmal zone s with buffer a reas such a s balc onies, ve randas, atr ia, courtyards and arcades, though divisions should avoid providing barriers to cross-flow ventilation if this is required. Enclosed courtyards or atria can save energy by functioning as spaces that bring fresh air into the building and provide natural ‘pre-heat’. Large balconies can have full-height adjustable sliding doors to serve as operable vents in cases where such natural ventilation is needed.
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In hot and humid climate such as Vietnam, natural ventilation is expected in almost every room. Cross ventilation through rooms is increased by large openings on both the windward and leeward sides. The rate, at which airflows through a room, carrying away heat with it, is a function of the area of the inlets
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and outlets, the wind speed and the direction of t he wind relative to the openings. The amount of hea t removed by a give n rate of a irflow de pends o n the temperature dif ference betw een the insi de and outside the building. •
Natural ventilation is generally suitable not only for selective areas such as the lift lobbies, staircase and toilets, which can have openable windows or air gaps to the exterior, but these should also be ventilated by a calculated percentage of air loss that is permitted to seep in from the air-conditioned spaces.
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The local wind direction is shown in Figure 2. For better natural ventilation, depth should be less t han 17 m etres for V ietnamese hig h-rise housing without a cour tyard [3 ]. The horizontal ve ntilation following traditional monsoon window as shown in Figure 4(b) should be encouraged.
4.4 Day lighting Daylighting provides more desirable and better quality illumination than artificial light sources. This reduces the need for e lectrical light so urces, thus c utting down o n e lectricity use and its a ssociated c osts an d pollution. Because of the cha racteristics of he ight, hi gh-rise ho using pre fers to use side lighting r ather than to us e toplighting. So, it is important to av oid direct su nlight an d con trol the rmal gain nea r the w indow [1 3]. Some usable principles are list as follows: •
Establish the location, sha pe, and orie ntation o f the bui lding o n t he si te based o n daylighting performance objectives.
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Almost all rooms, including kitchen and to ilet, need to receive daylighting d ue to e nvironmental and health requirements in the hot and humid climate of Vietnam. Window squares should be from 15% to 25% in comparison with the room’s floor square [3].
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Avoid excessive thermal gains and excessive brightness resulting from direct sunlight, which can impair vision and ca use discomfort. Use indirect lighting through reflecting ceiling and equip with traditional elements such as shades, screens, and light shelves.
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Transitional daylight designs can provide adequate daylight within about 4.6m of conventional height windows [15]. For the large plane, the inner courtyard must designed to improve daylighting.
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Integrate da ylighting sys tems w ith the ar tificial lighting system to maintain requ ired task to ambient illumination while maximizing the amount of lighting energy saved.
4.5 Passive Heating, Cooling and Thermal Storage Integration of passive heating, cooling and thermal storage features into high-rise housing can yield considerable energy benefits and added occupant comfort. Incorporation of these items into high-rise housing design can lead to substantial reduction in the load re quirements for bu ilding heating and cooling mechanical systems [13]. For Vietnamese climatic conditions, cooling is the prerequisite in the whole country. •
Passive cooling strategies include cooling load avoidance, shading, natural ventilation, radiative cooling, evaporative cooling, dehumidification, and ground coupling. Passive design strategies can minimize the need for coo ling thr ough pr oper selection of glazing, window place ment, shading techniques [13]. Some cooling strategies are listed a s follows: control external gains in th e hot time by scre ening (such as movable shutters, canopies and b linds) w here necessary and using p ale-colored wall and roof; use energy efficient appliances to minimize internal gains; ensure there is adequate cross-ventilation to t he
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apartment, and t hat s unspaces ca n be ve nted o utside; using ba lcony scre ens w hich are perfor ated facilitate the flow of ventilation air to the terrace and interior of the apartment; using enclosed courtyard or atrium to support passive stack ventilation; provide adequate cut-off between sunspace and bo dy of the dwelling; use vegetation, and water for positive cooling. â&#x20AC;˘
Passive solar heating is about keeping the summer sun out and le tting the winter sun in . It is t he least expensive w ay to h eat the house. P assive so lar hea ting re quires car eful app lication of the fo llowing passive design principles: no rtherly orie ntation of da ytime living ar eas; appr opriate areas of glas s on northern facades; passive shading of glass; thermal mass for storing heat; insulation and draught sealing; floor plan zoning based on heating needs; advanced glazing solutions. This will maximize winter heat gain, minimize winter heat loss and concentrate heating where it is most needed. Passive heating works particularly well in climates where many sunny days occur during the cold season. Attention should be paid to match the time when the sun can pr ovide daylighting and heat to a building when the building needs heat.
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Thermal mass storage can handle excess warmth; so a s to reduce the cooling load, while storing heat that ca n be slowly re leased b ack to the building when nee ded. The t hermal ma ss ca n also be coo led during the evening hours by venting the building, reducing the need for cooling in the morning.
5. Conclusion The de sign, c onstruction a nd o peration management of hi gh-rise b uildings ha ve a h uge i mpact o n t he environment and its resources. Passive arc hitectural des ign ca n have a huge impact o n land re sources savi ng, material sa ving an d ene rgy saving. A s a key elem ent o f sustainable b uilding, the passive de sign o f high-rise housing is significant. Nevertheless, high rise housing where passive methods are applied is rare in Vietnam. It is due to: the lack of understanding of what passive design can do in Vietnam; the lack of passive design research and a vailable community resources or ser vice w eather conditions; the lack of any strate gy of sp ecific an d innovative passive design. The design of high-rise housing in V ietnam should be em phasized according to the economic conditions, climatic characteristics and cultural traditions. Five points must be considered during the design process: i) configuration and orientation; ii) building envelope; iii) natural ventilation; iv) day lighting; v) passive he ating, c ooling a nd therm al stora ge. We sho uld ascertain c orresponding de sign o bjects and de sign principles and adjust and apply them to the design practice. This will ensure that high-rise housing in Vietnam integrates organically with the civil environment and develops toward ecological and sustainable building design practices. Passive design should become a national strategy regarding Vietnamese architecture in order to reduce building maintenance costs, to protect the environment and human health and to develop high-rise buildings in a sustainable way.
6. References [1] Charles, J.K. (2005) Sustainable Construction/ Green Building Design and Delivery, John Wiley & Sons- Inc, USA. [2] Do, V.T. (2006) An Approach to Sustainable Architecture for Office Building in Vietnam, The International Journal of Environmental, Cultural, Economic & Social Sustainability, vol. 2. no. 3, pp 51-65.
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[3] Giang, N.H. (2007) A Design Method for High-rise Housing in Ho Chi Minh city Following the Ensuring of Micro-climatic Conditions and Energy Efficiency Using, Master thesis, Ho Chi Minh City of Architect University, Vietnam (in Vietnamese). [4] Ho, D.C. and Tran, V.K. (2006) The Eco-housing in Ho Chi Minh City, In Proceeding Conference of Architects Association of Ho Chi Minh City, Vietnam (in Vietnamese). [5] Ho, D.C. (2006) The Basic Principles of Sustainable Housing Design, Final Research, Frank Lloyd Wright School of Architecture, America. [6] Hoang, D.K. (2004) The Natural and Hot-humid Tropical Elements in Composition of Architectural Character, Vietnamese Architecture Journal, vol. 12 (116), pp 24-29 (in Vietnamese). [7] Hoang, H.T. (2006) Vietnamese Ecological Architecture, Vietnamese Architecture Journal, vol. 3 (126), pp 48-52 (in Vietnamese). [8] Kamal, K.S., Wahab, L.A. and Ahmad, A.C. (2006) Adaptation Design of Traditional Malay House to Meet the Requirements of Comfort Living in Modern Houses, The Malaysian Surveyor Journal, vol.40, no.1, pp43-48. [9] Ngo, H.Q. (2000) A study on Vietnamese Architectural History, Construction Publishing House, Vietnam (in Vietnamese). [10] Olgyay, A. and Olgyay V. (1963) Design with Climate; Bioclimatic Approach to Architectural Regionalism, Princeton University Press, Princeton. [11] Sue, R., Manuel, F. and Stephanie, T. (2001) Eco house: A Design Guide, Architectural Press, Oxford. [12] Vietnamese Architecture Research Institute (1997) The Architecture and Tropical Climate in Vietnam. Construction Publishing House, Vietnam (in Vietnamese). [13] Xu, F., Zhang, G.Q. and Xie, M.J. (2006) The emphasis on Ecological Design for High-rise Buildings, Renewable Energy Resources and a Greener Future, vol. VIII-4-4. Shenzhen, China. [14] Yeang, K. (1998) Research information: Designing the green skyscraper, Building Research & Information, vol. 26, no.2, pp 122-141. [15] Yeang, K. (2006) Ecodesign â&#x20AC;&#x201C; a Manual for Ecological Design. Wiley-Academic. [16] Yeang, K. (2007). Designing The Ecoskyscraper: Premises for Tall Building Design, The Structural Design of Tall and Special Buildings, Wiley Interscience, vol. 16, pp 411-42. [17] Yeang, K. and Richards, I. (2007) Eco Skyscrapesr. Images Publishing.
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