Energy Efficient Roof Color
Name: Kathleen J.
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.
With some practice you can eyeball it, Kathleen.
Pretend you are color-blind, seeing in gray-scale, watching a black and
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%
Not that I am suggesting I have good taste.
The color of a roof would not matter if it had plenty of air ventilation
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?)
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.
Click here to return to the Engineering Archives
Update: June 2012