civil engineering - Are light coloured roofs more durable? If so, why aren't they more common? - Engineering Stack Exchange
If I run Google search for "roof" the pictures are typically of medium or dark gray, medium or dark green, medium or dark brown, brick red and other not very light colors - very rare are clay or sand coloured or similar colours roofs.
Neat image from Wikipedia:
Roofing materials nowadays are typically engineered (plastic coated steel, etc), not natural materials such as straw, and can have whatever color you please.
It looks like light coloured roofs absorb much less sunlight and so heat up notably less and this should prolong their lifetime. In my experience the key reason of dark ruberoid degradation is evaporation of resin because of sun radiation - it loses elasticity, basically turns into cardboard and then inevitably tears into pieces. I assume similar degradation processes happen in all materials that are either coated in plastic or rely on elastic resin for their properties.
Why are lighter coloured roofs not more popular? Is there any engineering reasoning behind this, or is it simply a design aesthetics choice? Does a light color roof provide any significant benefit from durability standpoint?
$\begingroup$ I not sure this relates to engineering. Depending on circumstances, the answers would be more about availability of materials, personal choice, housing fashion, aesthetic appeal, manufacturers offering choices to customers, architectural fancy, local building restrictions, local regulations requiring commonality of design and colours. $\endgroup$
$\begingroup$ I've added a couple questions to this to bring it around to the engineering perspective, and to ask a key question that I think will bring you to the real answer (namely, is there any benefit to a lighter shade of roof?) $\endgroup$
$\begingroup$ @TrevorArchibald Thank you. I had to partially undo the change because the question was about roof durability, not some abstract efficiency. $\endgroup$
You're quite right that it's generally beneficial to paint roofs white. It can significantly reduce cooling costs and can reduce heat island effects.
The only reason that I can see to avoid it would be in cold climates, where a black roof provides a bit of very cheap solar heat.
The problem is simply down to ignorance and aesthetics. Many individual home owners simply don't know how beneficial something so simple can be. Some don't believe it when you tell them. Some refuse to do it because they don't like the way it looks.
For more insight, look for news stories related to attempts by U.S.Secretary of Energy Steven Chu to promote this idea. He presented a strong, science-based case for painting roofs and roads. Reports form the time will give a good sense of the attitudes and politics involved.
Arguably, this isn't really an engineering problem.
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