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Name: Kathleen J.
Status: other
Age: 40s
Location: N/A 
Country: N/A
Date: 9/19/2004


Question:
I am building a house and want to make it energy efficient. I live in southern Alabama and have tried to find out about what roof colors will absorb the least amount of heat. I know that white is best, but white does not go with our color brick. Also, the builders in this region of the country are not at all concerned with ecology. They have been of no help. I have searched the Internet as well and have not found an answer to my question.

What color would best a brown roof (weatherwood) or medium grey (shadow grey)

Any help would be appreciated. I am trying to teach my children to respect the earth and be conservative with it resources.


Replies:
With some practice you can eyeball it, Kathleen. Pretend you are color-blind, seeing in gray-scale, watching a black and white movie. Whiter or lighter is better, blacker or darker is worse. Medium gray is exactly halfway between white and (boo, hiss) black. What I consider medium gray, usually turns out to be a little closer to black. Medium brown sounds about the same, equivalent to 40% white, 60% black. But I cannot be sure without seeing it.

To be highly ecological, you would need to lean towards light tannish browns or light grays. Light yellow is good too. All of which probably do not go with brick. Difficult. Maybe a two-color pattern?

Wood outdoors which bleaches to gray is often a little lighter than 50/50 gray, i.e. it is 60% white/40% black. This color is actually pretty light, as roof colors go.

Aluminum gray roof paint, slightly silvery, is an alternative that looks different than white but is similarly reflective of sunlight. It tends to have an albedo number of about 80%. That is, 80% white, 20% black. Not that I am suggesting I have good taste.

The color of a roof would not matter if it had plenty of air ventilation underneath, to carry away the heat before it gets inside, and a layer or two of fluffy & silvery insulation between ceiling and rafters to make sure. I guess that means attic fans. At least they are 100W instead of 1000W.

I often wonder if double-roofs could be made practical. (How to admit copious air, yet keep out the wildlife?)

Jim Swenson

PS- tubes of artist's paints sometimes have net brightness numbers on them. And computer photo-editing programs often let you put a cursor over any picture-spot you chose, and display the lightness number there.



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