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Energy Efficient Roof Color
Name: Kathleen J.
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: 9/15/2004
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 doesn't 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)?
Replies:
Kathleen -
I applaud the upbringing of your children.
Not knowing the exact colors you are dealing with, I cannot give you a
decisive answer, but I would suggest that your kids might find it
interesting to do the investigation for you in pursuit of your goal. Can
you acquire a tab of each shingle color? If so, place each of them in the
sun with a thermometer set behind them and record the change in temperature
over a period of time. (It would be good to insulate under your experiment
by placing them on something like bath towel.) Graphing the data wound
answer your question, and give your kids the idea that they are responsible
for your family's earth-friendly efforts.
Larry Krengel
Kathleen,
I am not sure that either of your choices will have a practical
difference over the other. I would pick the color you like best.
Bob Hartwell
Kathleen,
Thanks for your question and for teaching your children to be responsible
citizens.
The Department of Energy's Office of Energy Efficiency and Renewable Energy
(EERE) has a web site that discusses several options for constructing houses
that are energy efficient -- including roofing recommendations. Here is the
web site:
http://www.eere.energy.gov/EE/buildings.html
I hope this is useful.
Todd Clark, Office of Science
U.S. Department of Energy
When the color is constrained by other considerations as in your case,
probably the best thing to do is make sure that there is good thermal
insulation underneath the roof. This means reflective bats of fiber glass.
So even if the roof exterior gets very hot it cannot transfer that heat into
the house. An automatic temperature controlled exhaust fan from the attic
space to the outside also is very helpful in circulating hot air out of the
attic space and pulling in relatively cool air from the outside through the
attic vents.
Vince Calder
There are suppliers that ARE concerned about the reflectivity of various
roof surfaces. I did a web search of "reflectivity of colors" and found
several companies that would be happy to sell you roof coatings that reflect
most of the heat and thereby help to keep your house cool. Their "EverCool
White" reflects about 80% and their "EverCool Tan" reflects 70% (they say).
By the time you get to "Brown Tile" only about 5% is reflected (so 95% is
absorbed to heat you house.)
I suggest you search the web for someone in your neighborhood who is a
provider of high reflectivity roofs. I know nothing of these companies and,
for obvious reasons, cannot make any specific recommendations. It is
obvious, however, that a white roof reflects the most heat and so will keep
your house the coolest. Darker colors absorb more of the heat (black
absorbs all).
It is also obvious that there are companies willing to help you with this
project. Be aware, of course, that they are also willing to make a profit!
Best, Dick Plano...
I assume that you want a color that keeps the roof cool because Alabama
tends to be hot. I regret that I do not know which color would do that.
You would need to find out from the manufacturer what the optical absorption
is. Black would close to 100% and would be bad. White would be close to
zero percent and would be good.
If one is clever, one can use the light meter in a camera to get a rough
estimate.
Bob Erck
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