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> 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
> spray?
>
> 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
> summer?