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.
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.
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
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
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.
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
Figures someone would drag Limbaugh into the mix. Does
Rush write and publish Discover Magazine and/or the
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
On Tue, 26 Mar 2013 13:13:37 -0700 (PDT), " firstname.lastname@example.org"
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.
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.
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
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
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