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Cooling attic (and home) by spraying water on roof (shingles) - good/bad?
It's a mostly sunny day here (SW Ontario) and the mid-day outdoor
conditions are about 87 degrees and 50 to 55% relative humidity.
I have new shingles (100% asphalt, relatively light in color) on a
roof (pyramidal) with a 4:12 pitch covering an area that's about 36' x
40'. Large vent fan and 3 passive vents near the peak. Soffits are 2
foot wide on all 4 sides (but ventaliation is only good along 1 side
for the moment). Small fan is jury rigged in the attic space to
provide forced air circulation of the attic space and is powered with
the main roof fan.
Temperature sensor is positioned 1/2 inch from the underside of wood
deck - so I can read the air temp immediately under the decking but
not the actual deck or exterior shingle temperature.
Around 1 pm today the attic temperature read 120 degrees. I rigged up
some garden sprinklers on the roof and adjusted the flow to achieve
maybe 1 gallon per minute total flow. Naturally, the water exiting
the roof through the downspouts was warm to medium hot to the touch
(didn't measure the temp).
Within about 15 to 25 minutes the attic air temp was about 100
degrees, and it's almost 4 pm as I type this and the temp is 98.4
degrees (outside temp is about 87). I'm sure I don't have total
coverage of roof with water spray.
Since I'm currently re-working the soffits (adding pot-lights,
speakers, cables for CCTV, etc) I'm going to be running stuff into the
attic from the basement. I'm thinking that maybe it might be "cool"
to run a copper water line as well and permenantly mount a couple of
sprinklers that would give proper coverage to the roof and I could
turn on manually or automatically.
Is there anything written up about residential roof cooling with water
Are the benefits (reduced interior cooling load and increased shingle
longevity) outweight by (maybe) shingle dammage by water spray if the
water is used on the hottest, sunniest days in the middle of the
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