I have just purchased a Cape-style home with an unfinished second
floor. I would like to mount a large fan in one of the windows of the
second floor to pull air through the stair well from the first floor.
Whenever I look at fan literature, I see whole-house fans and
attic exhaust fans. The attic exhaust fans are usually quite small
and have relatively small capacity. The whole-house fans, on the
other hand, have much greater capacity, but are usually shown
mounted in a horizontal position on an attic floor. (The Cape of
course has no true attic.)
What is wrong with mounting a whole house fan vertically in
a window at the end of the second floor??? Or could two smaller
capacity fans be mounted vertically, one in each of the two
second-floor windows at opposite ends of the second floor?
Help much appreciated.
Attic fans are designed to pull air through the hot attic only, not the
capacity of a house. The whole house fans can be mounted in a window opening
if it suites your needs better. Most house fans you see today are the cheap
box fans that can sit on a window sill. Years ago, there were better made,
higher capacity fans for window mounting just as you intend. Now they are
harder to find. http://www.grainger.com/Grainger/searchresults.jsp?xi=xi
Grainger 4TM66 is probably something you could use.
Their $183 3C614 is also nice, and more efficient, moving 8908 cfm with
180 W (49 cfm/W) vs 3290 with 90 W (36 cfm/W) for the $73 4TM66.
Then again, a 2'x8' stairway door with a 24' height difference between
basement windows and gable vents might move 16.6(2'x8')sqrt(24'x10F)
= 4115 cfm with a 10 F indoor/outdoor temperature difference at night.
Whoops. Their catalog numbers are wrong, as firstname.lastname@example.org
pointed out. Grainger's tech support people at 847 535 5400 give this:
4TM66 3290 1520 1235 cfm
84.1 70.9 57.0 W
39 21 22 cfm/W
3C614 7005 6165 4160 cfm
364 280 185 W
19 22 22 cfm/W
Looks like the $73 4TM66 is the price and efficiency winner,
with a thermostat and reversibility, vs the $183 3C614.
<< could two smaller capacity fans be mounted vertically, one in each of the
two second-floor windows at opposite ends of the second floor? >>
Possibly a better idea. Most window sized fans would be aound 24" diameter to
fit in a typical 28" or 30" window. Checking some whole house fan sizes you
likely will see 30" commonly depending on your market area, difficult to fit in
most windows. And beside the higher flow rate, it's nice to be able to shut one
unit down to control air flow. HTH
Every true whole house fan I have seen are a LOT larger than 24". They are
at least 36" or more, have a large motor and a belt drive, and as you noted
are designed to be mounted in an attic floor/2 nd floor ceiling. Anything
that sits in a window is NOT going to pull air thru the entire house...at
least not in any meaningful way.
Now, I have seen these large fans mounted vertically in a sidewall/gable.
You also see them mounted this way in factory/industrial settings where they
function as exhaust fans.
My experience over the last 45 years has been quite different. In at
least four different residences (two of which were two story, 4 BR
houses), I have used a window-mount exhaust fan about 20-24" inches
in diameter. If tightly installed, they move a lot of air, and make
even warm and humid midwest nights relatively tolerable for sleeping.
In my current dry/cool night climate, I run one for about 1/2 hour
on summer nights, which is enough to drop the temperature of the
house quite substantially.
Mike Lacy, Ft Collins CO 80523
I grew up with one of these mounted in the upstairs window. It would
actually help you up the stairs when running.
The only issue I can think of is all of the dust and garbage in the attic is
going to be ejected by the fan. You will be pulling air from every where the
fan can. Low pressure air is not exactly going to go where you want.
If you were to open a window on the far side of the house the fan may pull
more air through the attic than up from the living area. This is why the
fans are usually mounted in the ceiling just above the living area. That way
they pull only from the living area and push the cooler air into the attic
I have a 20 inch round industrial type fan $40 bucks from Costco with a
remote control and a 9 incher as well. It is hung below the crawl space
opening in the garage. I turn it on about a hour after dark and woke up to a
home that was 67 degrees. It was 88 yesterday. Cooled to 62 last night.
Best you going to do is outside plus 5-10 degrees. Not bad considering the
Hope it works out for you
Well, I have one mounted at a 45-degree angle, and its fine . . . But
I would go with the others who have recommended getting a fan designed
to be mounted in a window. The whole-house fans are industrial
looking and noisy, and they have no safety guards. You would have to
build some sort of enclosure for it, and then take it down in winter
perhaps. It would be better to get something made for your
I thank you all for your suggestions. I have a friend who has a large,
belt-driven fan in one of his attic windows and it works superbly. But
it is a 30" fan and is only possible because it is an old house with
very large windows that can accommodate 30" in the lower sash.
My house can't do that.
I am inclined not to be interested in fans that don't have
shutters, which would eliminate the Air Kings. I simply don't want to
have to close the window whenever a heavy rain storm is imminent.
I will mull over your ideas now, and thanks again for all of
On 12 Apr 2004 12:45:58 -0700, heathcliff email@example.com
(Heathcliff Bambino) wrote:
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