I second the good advice given by Ed, Paul and Heathcliff. For the
WHF to be effective, you need periods where the outside air is around
70 or below and not excessively humid. In the Philly area, that
limits their usefulness to night usage in mostly the Spring and early
Fall. You could also use the WHF in summer if the AC has been off
and it's 85 inside, 75 outside, to drop the temp, then turn on the
AC, But if the humidity is too high, it's questionable if it's worth
it. If you have enough days where it works out for you, then it can
be worth it.
The attic fan is there to move air out of the attic so that it doesn't
get excessively hot. Before going with a fan, I'd make sure you have
maximum natural convection venting, ie ridge, soffit, gable etc. If
you can't get sufficient cooling that way, then a fan may be worth
it. However, either type of fan needs adequate attic ventilation to
be able to move the air volume.
There are a couple issues related to cooling your house.
(1) The house looks like it has a southern exposure, which means while
those skylights in what I presume is the living room will be great for
adding passive solar heat in the Winter, they are needlessly heating
the house in the Summer, unless you have shades/blinds over them or
(1a) Cover that arched window on the second floor! Sheesh - that's
adding all kinds of heat to that room (MBR?).
(1b) Consider awnings or some other form of shielding for windows that
receive prolonged Sun exposure. Blinds and shades are helpful, but
they don't stop the sunlight (in other words, heat) BEFORE it gets
inside the window.
(2) In our area of the country (I'm west and slightly south of you, in
western MD) the optimal insulation level in attic space is R50. Being
your house looks fairly new, I'm going to guess you have the paperwork
to check it out, or can contact the contractor who built it. The
reason R50 is helpful is not simply for holding heat in during cold
months, but for keeping the 120 degree heat of the attic in Summer
from penetrating to the upper floors of the interior.
(2a) Ventilate the living daylights out of the attic space in the
Summer, which means making sure you have enough soffit vents as others
have mentioned, and perhaps having a thermostatically-controlled vent
fan installed at one of the gable vents. While older models of attic
vent fans are noisy - I know from hearing them kick in at an
investment house I own - apparently there are newer models that are
whisper-quiet, as long as you don't mind paying a bit of a premium for
them (the same as with kitchen stove exhaust fans).
(3) Find an energy auditor to come to your home and do an assessment
to see where you can additionally save yourselves some coin on heating
and cooling costs. The Dept of Energy has links, and if you like there
is the Interfaith Coalition on Energy (www.interfaithenergy.com) right
there in Philly that is an faith-based group, which gives you a slight
modicum of reassurance that they're not in the business of energy
auditing to sell you products.
As far as the which-fan? question, I'm finding it darned-near
impossible to find a decently-constructed window-mounted fan that
could vent and allow me to cool off a couple rooms (my office, church
secretary, and library), so I would say you'll probably have better
luck finding a whole-house fan that vents into the attic than you
would finding a fan to mount in a window. Even though that means a
higher cost to install, what with having to have gable vents put in
: inside the window.
: (2) In our area of the country (I'm west and slightly south of you, in
: western MD) the optimal insulation level in attic space is R50. Being
: your house looks fairly new, I'm going to guess you have the paperwork
: to check it out, or can contact the contractor who built it. The
: reason R50 is helpful is not simply for holding heat in during cold
: months, but for keeping the 120 degree heat of the attic in Summer
: from penetrating to the upper floors of the interior.
: (2a) Ventilate the living daylights out of the attic space in the
: Summer, which means making sure you have enough soffit vents as others
: have mentioned, and perhaps having a thermostatically-controlled vent
: fan installed at one of the gable vents.
I'm in a similar situation as the OP, except for living in Tucson, AZ,
where the big problem is the attics getting extremely hot (160+
degrees) and radiating heat down into the living space. (I've come
to realize peaked roofs make utterly no sense in Arizona).
The consensus seems to be that getting the built-up air out is the key,
with air coming in from as low as possible (i.e. the soffet area),
exhausting it passively at or near the peak of the roof, and
making sure to have enough square feet of area in the inflow and
But there's remarkably little information out there about products,
a) soffet vents, other than cheap 16" x 8/10/12" perforatd metal,
b) ways of getting the inflow of air from the soffits up above
the attic floor and insulation (in an existing house).
I've been to three home centers and two roofing supply specialists,
all in Tucson, and no one has any range of alternatives for (a),
and none has a clue about (b). I was particularly
struck by the fact that the roofing supply guys really had no
idea there was even a problem in getting a clear pathway from
a soffet vent to the airspace up above the insulation. (In my house,
the roof slopes down enough that the sofets are about 3-4 feet
below the attic floor, and so 4-5 feet below the insulation
If anyone has any sources, even mail order, I'd appreciate the tip.
What I'm looking for for soffet vents is a continuous length
of peformated metal, that looks fairly nice, that could span
a 24" wide and 23 foor long area.
-- Andy Barss
On Wed, 29 Jul 2009 02:52:56 +0000 (UTC), Andrew Barss
If you look at the old Florida "cracker" houses before they had AC
here you will see a steep pitched pyramid shaped roof with metal
roofing (reflective) and a cupola at the top that acts as a natural
exhaust fan. They also have a porch roof all the way around the house
to keep the sun off the walls and out of the windows. They have lots
of windows and the cupola pulls the air in from the shaded porch and
out the roof.
If you translate that to an air conditioned house you have an
insulated ceiling above the conditioned space. The air intake for the
attic is generous air intakes in the soffits above the porch.
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