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I see a lot of variance in the prices of whole house fans in the market, and not a lot of clarity or comparison between vendors and models.

We're looking to buy some to install in our newly purchased duplex.

What are some things to look for and common issues or concerns with the installation and operation of these devices?

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Because I had no idea what it was: en.wikipedia.org/wiki/Whole_house_fan –  Doresoom Oct 1 '10 at 17:21

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I have one in my house, never really had a problem with it. They are a bit loud though, so put it someplace out of the way - putting it in the kitchen or living room or anyplace people like to congregate and talk would not be a good idea.

The only other thing to look out for is what happens in the winter. The big problem with ours is that while the louvers close automatically when it isn't in use, in the winter heat has no problem escaping through those louvers into the attic.

It might seem like a minor thing, but it's easily noticeable - in the winter my whole roof is covered with snow except for a bare rectangle directly above the fan. They make styrofoam covers that you can place over the attic fan, but that requires you to get up in the attic every winter and put it on, then take it off every spring, which can be pain if you don't have easy attic access.

Another solution (the one we use) is to use one of those window insulating kits (with the tape and plastic, where you heat it with a hair dryer) and put that over the louvers. It works reasonably well, but not ideal.

If you could get an attic fan that had some kind of real solution for this built in - say an automatically retractable cover, or one with a pull chain, that would be ideal. Not sure if they even make such a thing, but it's something to look for.

ETA: Another thing to watch out for - make sure your attic has plenty of ventilation. Those fans move a lot of air, and you'll need plenty of ventilation in the attic to make sure all that air can get out.

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Thanks Eric, for the insights. We do plan on getting insulated louvers, and a wind-turbine for the roof. I take it you have the standard pull-chain model? –  r00fus Oct 1 '10 at 21:31
    
@r00fus - The model I have doesn't have a pull chain. It actually has a switch on the wall (high enough that the kids can't reach it) to turn it on and off. –  Eric Petroelje Oct 4 '10 at 19:50

I have spent hours, even days researching whole house fans, and have found them to be one of the most cost-effective energy-saving home improvements one could choose to make.

After sorting through all of information out there, Here's what I'd look for:

Quiet operation - This allows you to run the fan during the coolest hours of the day (the nighttime, while you sleep) and get the maximum cooling effect. Dual speed operation is also nice, because the low speed is in many cases much quieter. Exchanging the air is important, which high speed can do quickly, and low speed can be used over night to cool the thermal mass of the structure down to the core. This way you can use your structure as a 'shield' against the heat the following day, and you can actually get more of a cooling effect with less airflow.

High Efficiency - If you are considering installing a whole house fan, you are most likely trying to save energy by reducing A/C use. So finding the most efficient whole house fan seems only logical. Some manufacturers have begun using ECM (electrically commutated motor) technology, which allows for AMAZING efficiency numbers -- and also extremely low noise levels -- especially on the lower speed settings.

Automatic, Insulated Doors - Unless you like crawling into your attic every season to insulate the hole in your ceiling (or if you live in a mild climate) you'd be better off finding a product that features mechanical insulating doors. Keep in mind that the seal created when closed is as important, if not more important, than the insulation level (R-level) provided. When shopping, ask whether or not the seal is maintained when the unit is off. Without a seal, it does not matter what the R-level is, and the insulation can not do its job.

Good luck in your search, and keep these features in mind when shopping.

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Our previous house had a whole house fan. I wired it up on a timer switch, so I could have it on when we went to bed, but have it shut off in the middle of the night. This cooled the house when we went to bed, but didn't pull the really cold air in early in the morning.

Most of the newer whole house fans are much quieter and energy efficient. Many of them also have insulating doors that automatically close. For more information, watch this video from Ask This Old House.

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