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

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The idea of painting roads and rooftops white in order to combat carbon emissions has been around for years. It is surprisingly simple and effective and yet has not been implemented much.
A study at the Lawrence Berkeley National Laboratory found that cooler pavement and roofs leads to cooler cities and an overall cooler world.
Since buildings with white roofs reflect far more sun than those with black roofs, these buildings stay cooler. Less air conditioning has to be used, lowering the overall energy required to run the building.
Also buildings with black roofs heat the space below them and this heat is carried spread by the wind. This raises the ambient air temperature in what is known as the urban heat island effect. Black roofs also radiate energy back into the atmosphere to be absorbed by clouds. This heat is then trapped by the greenhouse effect.
As such, white roofs is one of the quickest and most cost-effective ways to reduce our carbon emissions. In an initiative launched by the Energy Department, the federal government hopes to exemplify the benefits by using these light roofs on their buildings.
http://newscenter.lbl.gov/news-releases/2010/07/19/cool-roofs-offset-carbon-dioxide-emissions/
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I say it's total BS. The best study I saw on roof color was done in FL. They took a bunch of identical houses, put varying types and color of roofs on them, fully instrumented the houses, and measured during AC season.
The conclusion was that if you had a shingle roof, it made about a 10% difference in energy usage if you had a black rood or a white roof. And that was the energy usage with the houses unoccupied. They did another test when they were occupied and the energy usage difference dropped to just a few percent. Which makes sense, because when occupied the energy usage is going to be higher, because people are opening door, turning on TVs, cooking, etc.
It would also seem to me that it's junk science to suggest that lighter roofs lead to a cooler world. X amount of solar radiation is hitting the earth. Almost all of it is going to go into heating it. So, it's hard to believe that because something is white that radiation is going back from earth to outer space.
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On 3/26/2013 4:13 PM, snipped-for-privacy@optonline.net wrote:

Here's an aerial view of Disney's Epcot Center. Notice the white roofs. Disney knows what the fuck they are doing!
http://binged.it/YdDggm
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Per snipped-for-privacy@optonline.net:

I used to hang out at a beach near the yacht harbor next to the Ilikai hotel in Waikiki.
For years and years, the parking lot was just plain old dirt - light brown, somewhat dusty.
Then somebody got the bright idea of paving the parking lot with blacktop.
It made a huge difference. The parking lot area and adjacent beach went from being comfortable to being almost unbearably hot without a strong breeze to mitigate it.
So, unencumbered by any other knowledge, my money's on the white roofs...
--
Pete Cresswell

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There is also a big difference in artificial grass vs natural.
Driving around the city suburbs, it's often a relief to drive through a heavy tree area. Seems 15-20 degrees cooler.
Greg
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(PeteCresswell) wrote:

There used to be a nice breeze. Until they built the Ilikai which blocked the trades. Ala wai Harbor was much more comfortable before the Ilikai. For that matter, all of Honolulu was much more pleasant pre-high rise.
--

dadiOH
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Color isn't everything. Use reflectivity index. Higher energy cost is also meaning more energy creation, more heat. The insulation under the roof is going to be the main factor.
Greg
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On Tuesday, March 26, 2013 1:13:37 PM UTC-7, snipped-for-privacy@optonline.net wrote:

Was that based on stock white shingles or shingles painted white? Because surfaces painted white reflect roughly 90% of the sunlight, while regular white shingles reflect only 10%.
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Bob F;3037004 Wrote:

The difference between light reflecting off a mirror and light reflecting off a white roof is the difference between "specular" reflection and "diffuse" reflection.
[image:
http://academic.emporia.edu/aberjame/student/kuss2/15.jpg ]
Here's an example of \"specular\" reflection (off the cold calm water of Icy Bay, Alaska).
--
nestork

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wrote:

The last bit about reflecting heat back into space is true. But because roofs are so small the effect is insignificant. http://en.wikipedia.org/wiki/Albedo#Examples_of_terrestrial_albedo_effects http://en.wikipedia.org/wiki/Asian_brown_cloud#Global_warming_and_dimming
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wrote:

You can easily tell the difference with white cars and black ones in the sun.
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Then explain why when the experiment was actually done in FL, using white shingles vs black, it only made a few percentage points difference in AC energy usage for occupied homes. And then factor in that the percentage of the earth's surface that is covered by roofs is negligible compared to the total surface.
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On 3/26/2013 4:13 PM, snipped-for-privacy@optonline.net wrote:

Maybe thats what Limbagh told you but reradiation into space is an actual physical phenomena.
http://earthobservatory.nasa.gov/Features/EnergyBalance/page6.php
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.

uoted text -

Figures someone would drag Limbaugh into the mix. Does Rush write and publish Discover Magazine and/or the cited studies?
https://blogs.discovermagazine.com/80beats/2011/10/20/white-roofs-may-actua lly-add-to-global-warming/
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On 3/27/2013 9:42 AM, snipped-for-privacy@optonline.net wrote:

Don't know but your ranting sure sounds like the usual stuff from his groupies who just run with whatever "Rush said".

https://blogs.discovermagazine.com/80beats/2011/10/20/white-roofs-may-actually-add-to-global-warming/

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e

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quoted text -

- Hide quoted text -

And you sound like the typical lib elitist that drags Rush into anything and everything, claims he's said all kinds of things, but actually never listens to him.
Oh, and BTW, a better source for energy that reaches the earth not making it back into space would be Al Gore. He's the one telling us green house gases, caused by man, are trapping all the heat. So, which is it? It's being trapped or you can just reflect it all back into space from the ground?
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wrote:

>>http://earthobservatory.nasa.gov/Features/EnergyBalance/page6.php-Hidequoted text -

>https://blogs.discovermagazine.com/80beats/2011/10/20/white-roofs-may...Hide quoted text -

We should develop a car engine that burns greenhouse gas. That would be a very useful thing. Or, we could develop a car that runs on hot air. Al Gore would make a fortune..
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On Tue, 26 Mar 2013 13:13:37 -0700 (PDT), " snipped-for-privacy@optonline.net"

I've seen many model homes around Houston boasting energy saving features and they don't have white roofs so I think that proves you right. Our typical summer days are 95F but two or so years ago, we often had 102F summer days.
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.

Now it gets interesting. I went looking for the study done in Florida that I read just a month or so ago. I found the same study again, or I should say part of it. The original study that I saw consisted of instrumenting and monitoring the energy usage of 6 side by side houses in FL that were identical except for the roof type and/or color. As I posted earlier, the study showed that on a yearly basis, having a white shingle roof versus a dark grey one resulted in a 10.8% reduction in energy usage.
http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1220-00-es/roofing.pdf
But here is the interesting part. That 10.8% number is with the houses set at 77F and UNOCCUPIED. In the SAME study, when I previously saw it, it also contained a section on the results when the homes were then monitored OCCUPIED, but with the thermostats still set at 77F. And when occupied, the yearly energy savings dropped to just a few percent. The reason for that is obvious. The amount of energy saved by the white roof is going to be the same whether occupied or unoccupied. But when occupied the energy usage overall is going to be higher, due to opening doors, cooking, appliances, etc. So the percent savings of the actual energy usage is going to be a lower percentage.
It's interesting that part is gone. Now why might that be? Maybe it's because it's too real. I'm getting a new roof and was curious about the difference between a grey or black shingle. When I saw that in a real house, in FL of all places, going from dark grey to white only resulted in a few percent savings, I said forget it, the difference between black and grey isn't going to matter. And keep in mind that is for FL. I'm in NJ and in northern climates, what you save in summer is partly offset by increased heating costs in winter......
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there was some show on TV
there's a city somewhere in the midwest[?] that plants real green stuff on their rooftops, and they say it has had a big impact
marc
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