Building ‘green’ in Cambodia
Architectural principles and passive systems Geoff Pyle Pyle Architects
9 November 2010, Manolis House, Phnom Penh Copyright 2010, Geoffrey Pyle. Use may be made for educational purposes only; not for commercial use. All principles and figures should be reviewed and checked against actual conditions.
Green is one issue among many design criteria
Green design fundamentally affects the building
Green is more than just energy‌ Five groups of issues
1 The Site Current use of the land. Transport to and from. Control of pollution, including during construction. Solar reflectance and ‘heat-island’ effect.
2 Water Rain water absorption and run-off. Processing of sewage drainage. Collection and reuse of rainwater.
3 Materials Embodied energy. Recyclability. Waste (during construction and use). Sustainable timber.
4 Indoor environment and health Air quality. Pollutants. Daylight and views. User control of environment.
5 Energy Minimise energy demand through design. Lighting and cooling (design of building envelope, and efficient systems). Water heating. Renewable on-site generation may be possible.
Pre-design Three questions to ask‌
1 In designing green, where will we place our emphasis? If we cant do 100% of everything, what do we prioritise? This has to be decided for each project.
2 Are we going to assess how green we are and if so how? Will we do comparisons of carbon/energy/cost?
3 Will we validate it through an external organisation and get a certificate of green-ness? Possible benefits: assurance that green is thorough; most effective for capital investment; and marketing advantage.
Passive and active systems Outline approaches to temperature and the building envelope‌
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No air-con : basics - what creates thermal comfort? 1 Shade from direct sun 2 Limit radiant heat from surfaces nearby (insulation?). 3 Evaporative cooling from skin through air movement (fans or wind) assisted by water/plants if possible.
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Note: these slides show broad general principles, which should be reviewed in particular design situations‌
No air-con : insulated roofs (either flat or sloping)
Roof heats up; radiation from roof
OK
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Insulate roof to ‘cool’ the inner surface and reduce radiation internally
No air-con : insulation plus double roof
Only 50% of original radiation is emitted downwards
OK+
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Better than just insulated single roof
No air-con
High double roof
Only 50% of original radiation is emitted downwards
Due to distance between roofs, effect of radiation is reduced, so no real benefit in insulating lower roof
OK
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No air-con : walls similar in principle to roofs
Same principles apply to walls which are exposed to sun
OK
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No need to insulate if no sun on wall
No air-con : natural cooling at night may be effective Cross-ventilation; cooling the thermal mass of structure (concrete) at night - the concrete cools the space the following morning
Night cooling ventilation through floors may be possible 20
Air-con : typical - minimise heat gain from outside 28C-35C RH 70-85% 23C-25C RH 50-60%
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Air tight joints to prevent air leakage Insulation Limit electric lights by use of daylight Design windows carefully
Air-con : how to do windows
“The real cost of removing the heat that enters a building through the windows is so great that it is economic to spend considerable sums of money to reduce solar heat gain.� D G Stephenson, National Research Council Canada 22
Clear glass : about 80% of heat is transmitted Insulated wall : less than 5% of that through clear glass
Air-con : how to do windows Blinds are good for controlling glare but not heat‌
Blind heats up and radiates - not effective in keeping out heat Convection around the blind also brings heat into the room 23
Air-con : how to do windows
Glass heats up and radiateds from both sides
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Options for glass: • Reflective glass • Heat absorbing glass • Double glazing • Low-E coatings • Gas-filled • Combinations These are better than clear glass but cost more, and can reduce daylight, increasing demand for electric lighting. Not as effective as SHADING by a long way.
Air-con : how to do windows - shade Many options for shading glass/walls. Use sun path studies and video modelling. Note: if shaded, coloured glass is of no benefit. Consider also double-glazing and low-E coating for better performance.
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Designing a Building Envelope to be ‘green’ involves bringing together: Image of the building for the owner, both in terms of style and how ‘green’ the building is seen to be. External factors: orientation, climate, noise. Interior quality for users: daylighting, views, glare. Budget and materials available. Cost-benefit analyses of different approaches and understanding how extra capital expenditure is to benefit operating costs.
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Briefly on materials
Generally: Consider the ‘whole-life’ performance and cost. If higher-carbon materials last a lot longer - they may be more costeffective AND more sustainable.
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Briefly on materials
Insulation: Various types available in the international market, some more ‘green’ than others. More coming to Cambodia. Buy as ‘green’ a type as possible, but even if not, it is better to insulate well - to lower energy use.
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Briefly on materials
Structure: Steel not used so much in Cambodia, but is recyclable unlike concrete, and is more easily adapted. Concrete is being used overseas now with low-carbon cement substitutes, which reduce the amount of cement needed. For every ton of cement produced, approx. 1 ton of CO2 is produced from chemical reaction and the burning of fossil fuel. 29
Case study: residential resort in Siem Reap Rain water holding tanks reduce load on city mains drainage and allow use for irrigation. Sewage treatment on site means ‘clean’ water is discharged to city main drains.
WATER STORAGE UNDER BUILDING SEWAGE TREATMENT UNDER TENNIS COURT
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Case study: residential resort in Siem Reap Windows are shaded by balconies. Plants and trees refresh the air and lower temperatures.
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Case study: residential resort in Siem Reap Apartments and stairs are naturally ventilated, in ways which provide security. Roofs and walls are insulated. Hot water provided by solar panels. Air-con is ‘efficient’ type.
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Case study: Hun Sen Library extension at RUPP Mainly naturally ventilated, with some air-con spaces. Uses existing trees for shade and to provide confortable outside spaces for students.
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Case study: Hun Sen Library extension at RUPP Main reading area lit by daylight through glass with sun-screens (trees not shown here)
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Case study: Hun Sen Library extension at RUPP Main reading area lit by daylight through glass with sun-screens (trees not shown here). Ground floor is open for use by students, with view of water.
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Case study: Hun Sen Library extension at RUPP
Air-con spaces shown blue. 36
Case study: Hun Sen Library extension at RUPP
Holes in floor allow a little more night-time cooling‌ 37
Building ‘green’ in Cambodia
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