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Old May 2nd 05, 10:07 AM
Lacustral
 
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Default painting to cool house

Does painting the outside walls of a house white help much to keep it
cool? Do people living in the desert tend to have light houses?

thanks
Laura



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Old May 2nd 05, 11:11 AM
Edwin Pawlowski
 
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"Lacustral" wrote in message
...
Does painting the outside walls of a house white help much to keep it
cool? Do people living in the desert tend to have light houses?

thanks
Laura


Dark colors do absorb heat more than light. Good insulations is also
important.


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Old May 2nd 05, 11:32 AM
m Ransley
 
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If you are in the desert area yes. at 30f something black can be 40 f
warmer than something white measured with an IR thermometer. Do your own
test by an Infra.Red. thermometer at Radio Shack

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Old May 2nd 05, 11:44 AM
 
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Lacustral wrote:

Does painting the outside walls of a house white help much to keep it cool?


On a 90 F day, 1 ft^2 of R20 light-colored wall outside 80 F air would gain
(90-80)1ft^2/R20 = 0.5 Btu/h. A dark wall in full sun might have 250 Btu/h
= 0.1741x10^-8((T+460)^4-(90+460)^4), so T = 236 F, and (236-80)/1ft^2/R20
= 7.8 Btu/h, eg (7.8-0.5)8x40 = 2340 Btu/h more for an 8'x40' wall.

Do people living in the desert tend to have light houses?


They should, but some "planned communities" in Arizona specify _maximum_
reflectivities for walls and roofs, based on aesthetics... :-)

Nick

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Old May 2nd 05, 12:12 PM
Andy
 
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Lacustral wrote:
Does painting the outside walls of a house white help much to keep it


cool? Do people living in the desert tend to have light houses?

thanks
Laura


Andy writes:

Generally speaking, yes. The more "heat" you can reflect from
the surface of the house, the less is absorbed into the structure
which heats the inside.
A reflective metal roof will do wonders, also.

But bear in mind that the opposite occurs in the winter, when
it would be nice to absorb all the heat from the sun and the
surrounding that you can. I understand that the desert gets
really cold in winter, and you generally have to use more
energy to heat up something than to cool it off a few degrees, since
there is a mechanical advantage in BTUs of cooling, but you
usually have to burn something to heat.......

So, whether or not a really reflective dwelling is a good idea
depends pretty much on where you are located and the summer/winter
sunshine characteristics..

If you were to "re-paint" and "re-roof" twice a year, it might
work pretty good, but I haven't heard of anyone actually using
this fantastic idea of mine.... :)))))

If you shade your house with trees, you can accomplish the same
thing, and the neighbors won't mind...... Oops, I mean shade your
house with cactusseses.... :))))

Andy



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Old May 2nd 05, 12:39 PM
Joseph Meehan
 
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Lacustral wrote:
Does painting the outside walls of a house white help much to keep it
cool? Do people living in the desert tend to have light houses?

thanks
Laura


Yes and yes, but don't expect too much.

There is a larger effect for those living in a desert type area, and
remember if you live in an area that requires heating a good part of the
year, the reverse is also true.

I would look especially to the roof color. While a properly vented roof
will reduce the direct heat gain to the house a light roof will help keep
the roof itself cooler and help it last longer.


--
Joseph Meehan

Dia duit


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Old May 2nd 05, 01:25 PM
Buck Turgidson
 
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"Lacustral" wrote in message
...
Does painting the outside walls of a house white help much to keep it
cool? Do people living in the desert tend to have light houses?


Beyond the other responses, the website for the county that I live in
recommends shading your outdoor A/C compressor with a tree.


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Old May 2nd 05, 01:42 PM
 
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But bear in mind that the opposite occurs in the winter, when
it would be nice to absorb all the heat from the sun and the
surrounding that you can. I understand that the desert gets
really cold in winter, and you generally have to use more
energy to heat up something than to cool it off a few degrees, since
there is a mechanical advantage in BTUs of cooling, but you
usually have to burn something to heat.......


Since he would only need to heat the house at night, it really wouldn't
matter what the color of his house is, however.

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Old May 2nd 05, 01:58 PM
[email protected]
 
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Andy wrote:

If you were to "re-paint" and "re-roof" twice a year, it might
work pretty good, but I haven't heard of anyone actually using
this fantastic idea of mine.... :)))))


Maybe plants that lose their leaves in wintertime, eg grapes on a trellis,
over a dark wall...

Nick



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