Re: Cooling attic (and home) by spraying water on roof (shingles) - good/bad?

[Some Guy <Some@xxxxxxx>]

Dll wrote:

> "Some Guy"
>
> > 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?
>
> Funny thing is that a coworker tried this.  He said it made his
> shingles look really old quickly and didn't really do a whole
> lot other than that.
>
> Perhaps you are good (or bad) at math.  You might start by looking
> at the accuracy of your thermometer.  Only a few I know will
> discern accurately the 1.6 degree drop in temp you say, and
> they are expensive.

The thermometer I'm using is similar to this one:

http://tinyurl.com/d2u7x

It's an older version of the one on that page, except mine is
temperature only (so it shows simultaneous temps of both the sensor in
the unit and a remote sensor on the other end if a wire attached to
the unit).  Mine also shows the temp with 1 decimal place resolution.
When the remote sensor is brought close to the unit and left to
equilibrate for 10 minutes both readings agree with each other to
within about 0.5 degree.

Whether or not it is off by a few degrees compared with a calibrated
thermometer is not really the point.  If it shows a daytime attic temp
of 120 degrees and then later 74 degrees at night, and if other
sensors I have are telling me that it really is 74 degrees outside,
then I think I can rely on it.

> Did your living space get cooler?  Probably not.

Hard to judge, given the fact that my thermostat is on the main floor
and is regulating the AC based on the temp it is seeing on the main
floor.

It seems obvious that an attic with an air temperature of 100 degrees
would present a much better thermal load on the air space of the house
below it vs 120 or 130 degrees in the attic.

> Would a $50 attic fan do a 50x better job?
> They do seem popular.

This is with an attic fan going.

> I suspect there is a reason the world isn't equipped with
> roof sprinklers.

Houses aren't equiped with a lot of things - today or 10 years ago or
30 years ago.  My house was build in 1976 and (as I have discovered)
has 1/2 inch drywall panels directly behind the aluminum siding on the
second floor (no foam-board or styrofoam insulation panels).

But getting back to roof-mounted sprinklers, something like that will
never become part of standard residential construction because if it's
not done right it will more of a liability than an asset (freezing or
bursting pipes or condensation in attic, need for a good control
system, etc).

There is no doubt that water-cooled roofs in industrial/commercial
situations have been proven to be useful and cost effective (according
to some google searches I've done).  I can't find anywhere where
they've tried it in a residential situation.