Painting roofs white can actually help lower the temperature of a city

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On Wed, 27 Mar 2013 08:10:21 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

When I use to travel to Austin, Texas a couple years ago, going north on I-71, there was a place that I think is some kinda outside lab site for a local college which has solar panels and a small structure with grass growing on the roof. I never stopped there but thought it was interesting what they are trying to do. Do you have to eventually mow the roof <grin> ?
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On 3/27/2013 8:55 AM, Doug wrote:

in switzerland they grow plants on the roofs, but they let the cows mow them down.
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On 3/26/2013 3:13 PM, snipped-for-privacy@optonline.net wrote:

Your recollection of the study's findings is not completely correct. You're right that in its initial testing of unoccupied homes, it found an approximate 10% energy savings using a white roof. But it also found that while occupying the homes increased energy usage overall, there was no change to the amount saved by the lighter roofs:
"Additional monitoring took place over a month long period with the homes occupied, but the thermostat set points were kept exactly the same as in the unoccupied monitoring period. Although average cooling energy use rose by 36%, analysis indicated no decrease to savings or demand reduction from the highly reflective roofing systems. The added heat gains from appliances and people increase cooling system run-time, with longer periods for the duct system to exchange heat to the often hot attic space."
And the study's conclusion:
"In summary, this evaluation strongly confirms the energy-saving benefits of using more reflective roofing systems in Florida. Selection of colors with higher solar reflectance will result in tangible cooling energy savings for customers. This is particularly true for roofing materials such as tile and metal which are currently available with solar reflectances of 65%-75%. The selection of reflective roofing systems represents one of the most significant energy-saving options available to homeowners and builders. Such systems also strongly reduce the cooling demand during utility coincident peak periods and may be among the most effective methods for controlling demand."
http://www.mcelroymetal.com/content/greenbuilding/Florida_Power_and_Light_Study.pdf
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wrote:

The limiting factor here would be carbon emissions. The idea of white roofs making the house cooler is half a century old or more.

Thanks.
I didn't want a white roof because I was afraid it would look worse when it got dirty, so my next door n'bor and I replaced our roofs with light brown. I can tell the difference. Even when the roof fan is turned off, it no longer gets so hot on the second floor that I can't go there. It's always moderately comfortable on the second floor (and less hot than that on the main floor and cool in the basement) (I only use AC about 10 days a summer, and last summer not at all because it was broken.)
OTOH, I used to use the attic heat to heat the house the last part of fall and first part of spring, and the attic doesn't get hot enough to do that anymore.
In Indianapolis, I used to drive by the home of one of the richest guys in town, and the new home of his son. Brown asphalt shingles. By the end of the firs summer, the brown shingles were off and white shingles were on. This was about 1962. The benefits of a white roof have been known for a long time.
And check out your car. Why people buy black cars, with black seats no less, anywhere but the Yukon, escapes me. It takes more AC to cool them, and unless you use a remote starter, it's like Hell from the time you get in the car until the AC has finally cooled it off some. I have a light tan roof, white seats, and a tan steering wheel. I can get in the car, sit on the seat with short pants on, and touch the wheel without suffering on the hottest summer day, whether the convertible top is up or down.
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wrote:

When I was a kid, my dad being a carpenter put a white roof on our house (Long Island). I think it was either the only one or one of two in the large neighborhood. It wasn't too white as I recall (I was a youngster more interested in playing than construction then) so I don't think it showed the dirt that much but we moved away before it got to be near the end of its life so I can't say what it looked like then.
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http://newscenter.lbl.gov/news-releases/2010/07/19/cool-roofs-offset-carbon-dioxide-emissions/
I think they should paint the roads white, plant more trees and grass.
I was amazed with my only light plane flight over the desert. You could feel everything, roads, tracks, etc. Bump bump.
Greg
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Metspitzer wrote:

http://newscenter.lbl.gov/news-releases/2010/07/19/cool-roofs-offset-carbon-dioxide-emissions/
Igloos are built with white roofs and they remain very cool inside. :-)
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Bill
In Hamptonburgh, NY
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Someone should try black roof igloo. I propose a government study. about $5.5 million for start, and cost over runs and all. End up being about 20 million by the end of the year.
Christopher A. Young Learn more about Jesus www.lds.org .
Igloos are built with white roofs and they remain very cool inside. :-)
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Bill
In Hamptonburgh, NY
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On Wed, 27 Mar 2013 09:06:46 -0400, "Stormin Mormon"

Yeah and if they run outa money, just steal it from the SS funds.
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It takes a power plant to make that electricity, which makes the atmosphere warmer.
Greg
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It's easy to compute what's hot and what's not, and how much can be gained. Just take a look at the Landsat images from space. They started taking image scans of the earth in the mid 70's, with the multi spectrum image scanner. IR temperature of the ground is easy to detect. I think it actually used a rotating mirror to scan as the satellite moved over a hundred miles high looking at earth. Was first called ERTS satellite. environmental resource and technology satellite.
Greg
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Metspitzer wrote:

Could very well be true, but your HOUSE will look like shit!
Soot and other particulates will stand out on a white roof. Look around your neighborhood - do you see any white or light-colored roofs? Well, why not? And for those you DO find that are somewhat less than dark, don't they look ghastly?
Heck, you don't have to look at the roof; look at your very own brick work. Do you think that black mess GREW there? You know, the stuff you have to power-wash off every few years.
Yuck!
A white roof may very well be useful atop a 27-story office building but for a one or two-story residence, forget it.
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On 3/28/2013 6:07 AM, HeyBub wrote:

locality. in my neighborhood, every house with a flat roof (about 75% of all houses) is painted white.
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