I have a large front porch with a roof about 8 feet up. It is open on
the bottom so you see the sheathing and joists (2x6's). When the sun is
on it the heat really radiates down to the porch area making it hot as
hell even though you are in the shade.
I am considering putting up a "ceiling" but good circulation won't be
easy without a fan. The porch roof extends about 10 feet over the
original roof and shingles of the house so I suppose I could close it up
and add a fan. If I do it I'm thinking of using 3.5" insulation so
there is plenty of room for air circulation between the insulation and
Any other ideas before I get broiled?
1" Styrofoam, backed with aluminum foil, foil side up, against the
sheathing. Cut it into strips, making a snug fit pressing them between the
rafters. Available in 4 x 8 sheets. The white Styrofoam will look good too.
If you put the foil side "against the sheathing" then the
heat will conduct from the roof to the foil.
You could put the foil side under the rafters, facing in the
direction of the sheathing. It would also be a lot easier to
install, you don't have to cut the foam to shove it in
between the rafters.
I've considered ceiling fans but I don't know where I could properly
place them to do the job. I think ceiling fans would just blow hot air
all around me. If I'm lowering the temperature of the sheathing then
I'm transferring the heat from the sheathing and into the air. I just
don't see any easy way to use fans without a lot of turbulence, so I'd
be blowing hot air all around. I'm tired, does that make any sense?
BTW, the roof is 28' x 12' and a little more than a 1:12 pitch.
Yeah, ceiling fans without also insulating the roof probably wouldn't
help. I meant a fan/fans somewhere where they could blow/draw air
across the underside of the roof and out. That may not be possible
depending on the design of your roof, and is probably not your best
option by itself. I was just giving an example of how fans could
prevent radiant heating, in response to this statement: "A fan doesn't
stop *radiant* heat."
If you can't see it, that's a good trick. It's often done on commercial
buildings with flat roofs.
The reason you don't want to do it if the roof's visible is that turns an
icky color and stains from the junk in the air.
Sort of. If they're doing it right, they're using "roof paint" (not
sure about the exact name). It's a thick, insulating, reflective
paint. I've seen it in white and silver at the local DIY stores. It
may come in other colors, but if heat is your main issue, you want one
of those two.
Now, of your roof is in good shape and you're just looking to reflect
more heat, there may be other options I'm not familiar with.
on 7/26/2009 2:40 PM (ET) Tony wrote the following:
Home Depot. 'Henry's Solarflex 287 SF'. Comes in a 5 gallon can. I don't
remember the price. I painted my 20' x20' black asphalt shingle sunroom
roof with it 2 years ago. It made a hell of a difference in the inside
temps. Well, maybe 'hell' is the wrong word. :-)
The roof is still white 2 years later.
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