William,
My first company truck was a 1970 Land Rover 109 Diesel, that had
something called a "tropical roof", which was a second roof surface
(aluminum like the rest of the car) mounted on standoffs about 2" above
the actual cab roof. There were also scuttle flaps that allowed inside
air to be pulled out of the interior space by airflow, but the inside
roof of this car always remained at ambient temperature. I thought this
was such a cool idea (pun intended) that I incorporated the design into
a chicken coop I had at the time to try and keep the poor girls inside
from becoming baked chicken - it worked really well.
If you use a double roof as described, it doesn't matter what the
roofing color is, as long as the eaves are open and you have a good
ridge vent to allow proper circulation, and an air gap of about 3". The
only issue being the added cost, of course!
Matt T
Joel Davidson wrote:
William,
There's lots of good technical data (and also wild advertising claims)
on the www if you google "cool roofs". Smooth white roofs (metal or
non-metal) reflect heat well. Several years ago the US Bureau of
Standards tested composition shingles and found that so-called white
comp shingles got almost as hot as black shingles because of their
granular texture and asphalt subsurface.
It is worth noting that light gray or "white" asphalt shingles have a
measured solar absorptance of approximately 75% as opposed to true
reflective roofing systems which have absorptances less than 30%
(Parker et al., 1993B). Dark gray shingles have a solar absorptance of
about 90%.
...from http://www.fsec.ucf.edu/en/publications/html/FSEC-PF-336-98/
Joel Davidson
----- Original Message ----- From: "William Miller"
<[EMAIL PROTECTED]>
To: "RE-wrenches" <[email protected]>
Sent: Wednesday, September 24, 2008 9:05 AM
Subject: [RE-wrenches] Personal project: roofing colors
Friends:
I have an energy question on a personal project. We are adding two
rooms to our house and it is time to select roofing colors. Nothing
will match the weird comp shingles already on our roof, so we are
going to not match and re-roof the rest of the house later. In the
meantime, I need to pick a shingle color. How much difference does a
lighter roof color make here in our inland California (Mediterranean)
climate? We get over 100F frequently in the summer.
Thanks for your insight.
William Miller
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