We have a pending roofing project. In selecting colors, black is very hot. A new color is on the market -- a dark blue green. Would this be much better? It's not a light color.
Unfortunately, with new technology, it isn't always easy to tell which color roof is going to keep your attic space the coolest. Probably the two most important engineering factors for this are absorption or relectivity. The absorption coefficient will tell you how much heat energy the shingles will absorb and the reflectivity will tell you how much sunlight the shingles will reflect. Low absorption and high reflectivity would seem to be what you want in the ideal situation. In the real world, with a properly ventilated attic, it really doesn't make a lot of difference. With small ventilated spaces, like cathedral ceilings, it could make a difference.
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Unfortunately, with new technology, it isn't always easy to tell which color roof is going to keep your attic space the coolest. Probably the two most important engineering factors for this are absorption or relectivity. The absorption coefficient will tell you how much heat energy the shingles will absorb and the reflectivity will tell you how much sunlight the shingles will reflect. Low absorption and high reflectivity would seem to be what you want in the ideal situation. In the real world, with a properly ventilated attic, it really doesn't make a lot of difference. With small ventilated spaces, like cathedral ceilings, it could make a difference.
The coolest colour is white.
However, a lot of the heat that finds its way into a home is by radiation and conduction.
Conduction via the fabric of the roof through to the interior of the home.
Radiation across the loft space to the fabric of the roof.
The only way to avoid conduction and radiation is to line the inside walls and ceiling of a room with at least five inches of polystyrene, glued to the surface.
Mechanical fixings that act as heat bridges must be avoided.
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by Dave-Morris » Mon Apr 13, 2009 6:49 pm 
by cromagnon » Sun Sep 06, 2020 10:18 am
