| meirman 2005-07-17, 4:25 am |
| In alt.hvac on Sun, 17 Jul 2005 01:44:13 GMT
"rlsusenet@NOSPAMPUHLEEZschnapp.org" <NoSuchPerson@bigfoot.com>
posted:
quote:
>Robert Morein wrote:
>
>Interesting question. I wonder if anyone has tried to develop a
>long-lasting thermoochromic paint that's dark when it's cold, and light
>when it's hot. Hmmmmm...
I'm not sure one would ever want it dark, at least for a roof. Doesn't
a dark roof also radiate more heat in the winter, when owners would
rather have their attic warm?
That's why Robert asked about ice buildup with white.
Actually the light tan colored roof that I mentioned probably is't
light enough to worry about ice, but I turn off my roof fan in the
spring and fall to try to absorb heat during the day, and use it to
heat the house at night. I'm positive this worked before, at least on
the occasional hot days during those seasons. I'm not sure it's
working so well now.
And it's not like my attic is any cooler during the summer, except for
late morning. The roof fan turning on later and off earlier, to the
extent it probably does, saves me money, but I don't think it makes
the house any cooler.
In a few years the roof fan motor will need replacing again, and it it
is summer when it does, during the two to four days it takes me to get
around to replacing it, I should be able to see how much difference my
light tan roof makes.
quote:
>I used to have a mug from Science News that had thermochromic printing
>on it. It was dark brown at room temperature, and clear at above 120 F
>or thereabouts.
>
>There are some interesting Google results for thermochromic pigments
>(http://tinyurl.com/9zwej) that might be very useful in this
>application. A nice black pigment that transitioned to white or clear
>(painted over a white base, say) at around 80 F could be very handy for
>painting roofs. Make it in some more interesting dark colors, and it
>might be pretty good on south (north, in the southern hemisphere) or
>west-facing walls.
>
>Gee, I'd think there ought to be some significant money in such a
>product! Unless, of course, the pigment is hideously expensive, or
>degrades too quickly.
>
>My Science News mug eventually stopped reacting to heat.
Meirman
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