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

["Phil Scott" <philscott@xxxxxxxxxxxxx>]

"Jim Baber" <jim@xxxxxxxxx> wrote in message
news:orKdnX-MIND1ZiPfRVn-sQ@xxxxxxxxxxxxxx
> Jim Baber's comments:
>
> wkearney99 wrote:
>
> >>Is there anything written up about residential roof
cooling with water
> >>spray?
> >>
> >>
> >
> >Besides the glaring fact of WASTING WATER?
> >
> Bill has a point here, but if you were to use misters (like
I do between
> my solar panels and my roof), you might see the same kind of
drop in
> attic temp that I have had.  My roof that has my solar
system is a 6:12
> pitch facing due south.  I have noticed a 10 degree
reduction in the
> attic temperature just due to the shading by my solar
panels, down from
> 160 to 150 deg. on a 100 degree day.
>
> I installed those commercial cooling misters for patios and
yards,
> behind my solar panels to cool the panels themselves,
figuring that I
> did NOT want mineral deposits on the front.  I was not to
worried about
> roof deposits, because I intended to only run the misters on
days over
> 90 when I had measured a drop in power generated by the
panels because
> of temperature degradation above 95 degrees.
>
> This supposedly only uses about 2 gal. an hour per the Mfg.
claims, and
> has not deposited significant or noticeable minerals in 2
years of
> operation.  The roof does get damp sometimes but not
usually, since
> there is considerable convection air flow upwards behind the
panels that
> evaporates most of the mist before it wets the roof.  I do
use a
> demineralizing cartridge in the supply line, and they are
available
> where I got the misters.
>
> When I turned on the misters behind the solar panels the
temperature
> dropped an additional 30 degrees in the attic to 120
degrees.  This
> isn't cool by anyone's idea, but I noticed that the A/C has
reduced the
> number of minutes the it runs each hour by about 15% on
those 100 degree
> days we have too many of here.
>
> By the way the misters also accomplished what I wanted in
the first
> place, I got back the 0.83 kW of peak solar production I had
lost
> because of the solar cell heating. (that's about $1.62 for
any day over
> 90)   All in all I found it to be a very worthwhile effort
since we had
> 67 days over 90 last year for an additional estimated
$108.00 worth of
> power we produced.  I have not estimated how much the
reduction in A/C
> time was worth but I could from the cost of running it vs
not running it.


Misting is a vastly under used technology... sounds like you
have a great application there.    Ive been trying to sell it
to super markets with air cooled refrigeration for years... a
tough sell..but it would save them a bundle and cut repair
costs.  There are commcl systems on the market for that
application but they dont sell well.

They sell for chicken ranches and misting public areas the
desert mostly.

Phil Scott

>
> >Do the math on your water bill ............
> >
> >
> At 10.8 gal. a day for 67 days that's not much water, but I
can't put a
> value on it since we are not metered at all.  You could put
a value on
> it at your cost, but I can't even make a guess as to that.
>
> >........ (or the electric to pump your own well water) and
you'll probably find it's
> >a helluva lot cheaper to just leave the roof alone.  If
anything, put in an
> >attic vent fan.  Water's not as harmless a material as one
might imagine.
> >The various minerals causing deposits, the likelihood of
algae other
> >mold/fungus growth and even it's weight are all factors to
consider.  Enough
> >that unless the roof was designed with in mind would make
it not only a bad
> >idea but a potentially dangerous one at that.
> >
> >-Bill Kearney
> >
> >
> I can't see how it would be dangerous, in fact in So. Calif.
some people
> do this for protection from brush fires,  and I would do it
here if I
> still had a shake shingle roof.
>