Wednesday, October 15, 2008

Alternative Roof Forms for large Thai buildings

Hi Valerie,
Thanks so much for the solar model studies. I think this whole question of an appropriate roof form is going to be a major challenge for us. Here are some preliminary thoughts:
- not very Thai, but are there precedents?
- lighter loads on the structure per m2
- shorter columns
- greater wind uplift
- greater risk of leaks
- more Thai, greater 'presence'
- scope for attics/mezzanine floors within roof space
- High walls or windows under high roof eaves (in gable walls, or high walls under mono-pitch roofs), adding cost and maintenance issues, but enabling better high level ventilation and daylight.
- Greater overhang and/or sun screens required on north side (assuming this is the higher
side in a mono-pitched structure) to protect facade from direct sunlight
- larger cross-walls required, with greater cost, need for piers or other stiffening
- design of roof eaves on high and low sides of monopitch roofs to reduce wind turbulence and encourage cross ventilation.
- what is the optimum pitch of a monopitch roof to encourage cross-ventilation? This will need to take account of different conditions at different times of day and year. How is the 'stack effect' of such a roof reduced by thermal insulation in the roof? Maybe it's important to distinguish between quilt insulation and foil insulation (ie reduce UV transmission
rather than conducted heat).
-how is cross-ventilation effected by the width of a building, relative size of windward and leeward ventilation openings etc?
-How many of these variables can be tested by computer modelling?

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