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

[Some Guy <Some@xxxxxxx>]

Jim Baber wrote:

> >Besides the glaring fact of WASTING WATER?
> >
> Bill has a point here, but if you were to use misters

Doesn't a mister waste water by atomizing it and then the wind will
blow it away?

I would think the ideal way to cool something with water would be to
completely wet the surface of something you want to cool with a low
volume of flowing water.  That would avoid staining from minerals in
the water.  The heat you're taking away is the difference between the
inflow and outflow temp multiplied by the volume flow rate.  Some
evaporation will also happen.

I know that water can cool best if (all of) it evaporates, but that
will leave mineral stains, and also it probably won't get you down to
the low temps you can reach by continuous flowing water.

My tap water comes from lake Huron and is probably around 50 degrees
(f).  I pay 3.86 cents (CDN) per cubic foot (3.165  USD).  I think
that's about 0.516 cents (CDN) per US gallon (or 0.423 cents USD).

I pay 5 cents (CDN) per kWh for the first 750 kWh (per month) and 5.8
cents per kWh after that.  That's about 4.1 and 4.8 cents USD
respectively.

> At 10.8 gal. a day for 67 days that's not much water

That's 5.6 cents (CDN) per day, or $3.74 (CDN) for 67 days ($3.06 USD)

> > The various minerals causing deposits, the likelihood of algae
> > other mold/fungus growth and even it's weight are all factors
> > to consider.

Deposits, yes - but perhaps negligable if the water is not allowed to
evaporate.  Mold/fungus - I'm thinking no because this would only be
used on mostly sunny days for maybe 1/2 hour to maybe 2 hours of the
day.  When the water is turned off, the roof will dry up and I
wouldn't think that would give any mold or fungus any ability to grow
given that the shingle temp would probably climb back to well over 100
degrees.  A thin layer of flowing water on the roof is equivalent to a
gentle spring or fall rain shower and nowhere near the weight of the
snow loads we see during the winter.

PS:  Given gasoline costs at $2 to $3 per gallon (or $1 CDN per liter)
what are the costs to generate electricity (on a kWh basis) using a
gasoline powered generator?

PPS:  Are there gasoline or propane-powered AC units, and are they
more economical to run vs electric?

PPS:  What are the pro's and con's of immersing your outside AC
condensor coil in your swimming pool (and therefor doing away with the
cooling fan) ???  Heat your pool and remove heat from the coils much
more efficiently?