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Master Brian 05-12-2010 06:59 AM

whole house fan
I have a 1915 Craftsman Bungalow, with 1-1/2 stories. I would love to install a whole house fan in the ceiling above the 2nd floor, but I am curious if I have enough attic and venting above this space. I don't have an easy way to measure the attic, but it is only about 6-7' wide at the bottom of the ceiling, so I'm guessing maybe 3-4' wide in the attic itself with about 2' of height. I can crawl through there, but it is tight.

This is a gable roof, but no gable vents and haven't found a good way to install any. There is 1 roof vent and two turbines, that is it for venting. I have thought about installing some ridge vents, but not sure how much, if any, they would help in this area.

What I'd like to accomplish is with open windows in main part of house, I'd like to draw the warm air from 1st and 2nd floor up and out the ceiling of the 2nd floor. The problem is when I've researched these fans it appears I don't have near enough venting in the attic for them to work correctly. So I'm looking for options.

The 1st floor is just over 1300sq ft, the 2nd floor is about 700sq ft.

RoyalAcresRod 05-12-2010 07:43 AM

I would research the various fans you are considering, paying particular concern to the manufactuer's recommendation for the amount of venting area required. You'll have to provide this net area somehow....either through gable or roof vents, IF you are installing in second floor ceiling.

If you cannot provide this net area throough the gables or roof, the only other option I see is a fan on the second floor, perhaps through the wall or a window. There are whole fans made for horizontal wall installation.

A whole-house fan, of course, only works if the intake and outflow are equalized.

Where are you located? In some parts of the world, you can bring in so much humidity that your A/C has to work overtime to remove it. Don;t know if that's a factor with no location...

Master Brian 05-12-2010 11:09 AM

As I was typing this, I was actually wondering about using a fan mounted to a window. I am somewhat working towards finishing off an attic area, which is adjacent to my 2nd floor living area. The area is a gable end and will be used as a storage/walk-in-closet area. It has a standard door leading to this area and I could also easily install a couple of "return air" type grills to the wall(s). This attic area also has a fairly large window, about 18"x28", which is used to help vent the attic in the summer. I suppose if I could find a fan that would fit the window, I could rig it up so that during the spring/fall I install the fan, then remove in the hot and cold months when I'm running the a/c or furnace.

I'm in south-central Kansas and would only want it in the spring/fall/very early summer months. I know others have the whole house fans and love them.

RoyalAcresRod 05-12-2010 11:27 AM

Although I cannot say definitely that one is not made, the whole house fans that I have seen have of course all have a square form factor, and the sides are a lot bigger than 18 inches....I doubt and 18X18 fan would give you enough flow to make this venture worthwhile.

Too, the larger the fan blade, the smaller the angle of attack, so to speak, of the blade. What I am trying to express is that for any given CFM, the smaller the fan, the larger the amount of noise which is going to be created. A small fan which would fit in this area might make an objectionable amount of noise. A physically larger fan can spin much slower for a given CFM.

IMO, I believe your best bet is too permanently install a fan in a suitable wall space, with provisions to insulate the fan with rigid insulation during the off-season, rather than rigging up an insufficient sized one which will not do the job.

I'd first do research on the size of fan necessary for your structure...then we can discuss, especially with all the smart folks around here, the options you have as far an installation.


Yoyizit 05-12-2010 11:43 AM


Originally Posted by Master Brian (Post 440752)
it appears I don't have near enough venting in the attic for them to work correctly. So I'm looking for options.

It depends on the fan curve. Look for CFM vs. static pressure. The manufs have an interest in helping you with this.
Fans for evap. coolers have to work against enormous back pressure.
Decide on your desirable CFM [Air Changes per Hour, ACH] and calc. the back pressure that your venting gives you.

High Gear 05-12-2010 07:24 PM

Better scrap the ceiling mount fan with only a 2' attic clearance.

Even with a ridge vent it would still be like a wind tunnel in there and blow your insulation out of the vents.

Here's a link to fans.

Master Brian 05-12-2010 07:31 PM

That's kinda of what I thought, but figured I would ask anyway. I do have an approx 12'x12' room with a hip roof that sort of ties into the other, but I seriously doubt it's enough attic space either and I don't want the fan in that room.

I'll check out the grainger site and next time in the attic, I'll try to get a measurement of actual attic space....

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