# insulating a whole-house attic fan



## RustyShackleford

I have a whole-house fan (attic fan ?), a roughly 3-ft diameter fan that sucks a LOT of air out of the house (and thence out the ridge and soffit vents).   It can be nice in the shoulder warm seasons and when I have a merry mix-up with the woodstove or in the kitchen. But, the only thing standing between the loft/cathedral-ceiling area and the cold cruel world is a 3x3ft metal contraption of louvers that automatically open when I turn-on the fan.  They seal fairly well, but have absolutely no insulation, and I hate to think what the R-value (or, more to the point, the U-value) is.   If I stick my hand up though the louvers, it doesn't feel cold up there, and I'm like "duh, yeah, I'm heating the frickin' attic".  

So, what to do ?   These fans are so common that I can't believe there's no product available.   Another option is to build something.  I'd build a box of 1x4s surrounding some 1x4 T&G planking (like that on the ceiling) or maybe some furniture grade plywood, with a couple layers of blueboard and a lot of weather stripping.  The thing would be hinged on one side.   It's in the loft, so I'd have to go up there and open it when I need to run the fan, and of course it'd be in the way at that point.

That's the best I can come up with so far.   Any better ideas, or a product I'm missing ?  Thanks.


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## CALJREICH

Well I don't know but I would get something a batt of insulation or whatever to lay over it for the time being until I figured a permanent solution.

Is there a duct that goes from the fan out? I think I would go to lowes or someplace that sells them and find someones brain to pick.


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## Beetle-Kill

Rusty- the next time you're in a grocery store, walk in a back room and check the temperature difference. I say this because you'll probably have to walk through those clear plastic , hanging curtain things. can you incorporate that idea? Build a shroud enclosure and hang something in front of it? A picture would help me visualize this thingy.


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## Dune

Build a box out of 1/4" plywood and line it with 2" ridigd foam. Attach it over or under the louvers (wherever it can fit) . Leave it up there all winter, then take it off for the summer.


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## peakbagger

A quick solution thats is better than nothing is Frost King whole house fan louver cover. I have one in box waiting to be installed next week. Its basically and insulated "fabric" cover that covers the louvers and is held on with velcro. I currently just throw a couple of bats of fiberglass over the opening in my attic but still get drafts. If the new cover doesnt work, I plan to make up a hatch over with a birch plywood face with foam on the backside and mout it with shutter hardware so I can take it off in the spring.


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## Later

Build a box out of the foil covered 2" frigid foam and set it over the fan in the winter


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## Huskyforlife

Buy a 2" R-10 foam sheet and a roll of foil tape from Home Depot.  Build a box out of it with the tape.  You can double or triple layer if you so choose.  Seal it airtight with the tape.  It's the method I use for our in-wall A/C units.


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## RustyShackleford

Thanks for the ideas, guys.   I would like it to be easily openable, so I don't think I like the ideas that involve putting something over the backside (aka. top) of the fan (where I'd have to go up in the attic to remove it).

The fan is mounted horizontally in the ceiling of the loft, no ductwork.

The Frost King product sounds interesting; I'll check it out.


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## Flatbedford

I cut some 2" foil backed rigid insulation board pieces that fit in the fan opening. I remove the louvers, put the insulation in the opening and reinstall the louvers. The insulation is out of sight and I can do this without going in the attic. I should go back in there and tape up the seams though.


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## iceman

I buy the plastic shrink wrap for the windows and go right over - easy and keeps the warm air from getting out


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## Seasoned Oak

I have the  same fan in my house and im still going over ideas.  But im inclined to put something over the back of the fan.


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## mikeyny

I am not a big fan of those whole house fans. I have seen many instances where the fan has pulled the flue gas (exhaust) right out of the gas fired hot water heater  and caused some high levels of co in the house. This usually happens in a house that is fairly tight with good windows and insulation. I, personally would remove it if I were insulating my attic. They are a HUGE heat loss in the winter.
                                                                                                                            MIke


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## iceman

mikeyny said:
			
		

> I am not a big fan of those whole house fans. I have seen many instances where the fan has pulled the flue gas (exhaust) right out of the gas fired hot water heater  and caused some high levels of co in the house. This usually happens in a house that is fairly tight with good windows and insulation. I, personally would remove it if I were insulating my attic. They are a HUGE heat loss in the winter.
> MIke






Yes they can be dangerous when not used properly, just like our stoves and furnaces etc...
I only use mine in the spring /summer .. but try to open all my windows and doors in the house , or if its hot open all windows on the basement 1st floor level so I don't suck any of the hot air exiting the house back in... 
And usually in the morning it will cool my house enough so the ac doesn't kick on till the after noon..
But I did have a friend who co detector kept going off and it was because of the fan ... he never opened windows so yes it did pull his hot water tank exhaust ... it was a lesson learned!


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## RustyShackleford

I'm always careful to make sure there is plenty of crossflow from open windows and doors when I activate mine.


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## fishingpol

There are products out there.  I did see a foam cover at a big box store.  It looked like and upside down wheel barrow without handles or wheel.  If you build one, use 3/8 or 1/2 plywood and make a box and glue rigid foam to the inside.  Look on the internet for magnetic stick on vinyl sheets that can be used from the living space.


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## Seasoned Oak

mikeyny said:
			
		

> I am not a big fan of those whole house fans. I have seen many instances where the fan has pulled the flue gas (exhaust) right out of the gas fired hot water heater  and caused some high levels of co in the house. This usually happens in a house that is fairly tight with good windows and insulation. I, personally would remove it if I were insulating my attic. They are a HUGE heat loss in the winter.
> MIke



Mine all but eliminates the need for Air -Cond in summer. As long as the nights are cool which 99% of the time they are here in central PA i cool the house down over night and have no need for AIRCON the next day. I use electric hot water in summer so no back draft. Insulating the fan for winter is a small price to pay for the benefits in summer.  If my next house dont have one ill put one in,never be without it.


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## maverick06

I just built a box out of 2" pink foam and gorilla glow and put it on top of the fan (I had to build it in the attic as it is larger than the little drop down stairs allow. It seems to work well... I guess, this is my first winter. When i point my IR thermometer at the cieling I and then at the louvers I get the same reading, about 62....now when i point it at the pull down staird (center, not even the edges, I get 52... lots of heat lost there. 

The attic fans are amazing, life altering pieces of equipment. My powercompany also gave me $90 back for installing it! (i should go and make sure that check cleared.....)

Not sure if it is the right way to do it, but thats how mune is insulated, no foil nor wood, just foam and glue.


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