A DIY Whole House Fan

Our DIY whole house fan.

How hot is our unairconditioned, uninsulated old house? Kelly has temporarily banned bread baking and I’m thinking of opening my own Bikram hot yoga franchise.

But seriously, a few summers ago I decided to install a whole house fan. What’s a whole house fan? It’s a large fan, mounted in the ceiling, that pushes hot air into the attic while simultaneously drawing cool air in from the outside. You turn on a whole house fan when the air outside is cooler than the air inside the house, usually in the evening. It works best in climates that have hot days and cool nights–like Los Angeles or many other parts of the Southwest.

Diagram from Gear Hack.

Whole house fans are usually placed in a ceiling towards the middle of the house. For us that’s the hallway. Unfortunately, between the attic access door and the intake for the central heater, our hallway ceiling had no room to fit a standard whole house fan. And I’m cheap. So I decided to make a DIY version.

I picked up a shop type fan and installed it in a 3/4 inch piece of plywood cut to fit the attic door. It was a simple project and saved a lot of money. I think I spent around $30 for the fan and used a piece of scrap plywood. I added two handles to make it easier to remove the fan/door and access the attic. The final touch was to install an outlet in the attic wired to a switch hidden in a closet so that I can turn the fan on and off. When cooler weather comes around I simply swap out the attic fan for the normal attic door. Would a commercial whole house fan work better? Yes, but I try not to let perfection be the enemy of the good around here.

An attempt to use a bike pump as an air conditioner. Hot cat in background.

It’s still damn hot at Root Simple world headquarters during the day. So maybe I will open that combination bakery/Bikram yoga franchise where you can eat buns while you tone your buns.

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  1. “…I try not to let perfection be the enemy of good around here.”-well said. That is my problem, and I need to have that mind shift.

  2. I got a real kick out of your picture. You are ‘down the hill’ and a bit over from me and I know you are suffering as much as we are in CA ‘High’ Desert. Of course we say ‘But it’s a DRY heat here’ so tho it’s hotter here it probably feels the same there. But being without a.c. for 3 days here sucked. Thank goodness it is now fixed!
    Do you have those ‘roof vents’to take the hot air outside? They help to keep the attic cool. I put then in my LA house years ago and they made a 10* difference.

  3. I open all the windows (well, all the windows that currently work, SIGH) and turn on the a/c fan (but without the a/c) engaged. It helps make our 1973 mobile home a little more tolerable at night. I like this idea and may do it, but will have to hire out the labor (our ceilings are weird and I don’t want to be the one to cut it open). Thanks!

  4. Sounds like it is time for a DIY Swamp cooler, I would think you are dry enough (humidity wise) there for that to work! Same basic concept but you are pulling the air though a large wet sponge and pushing it through the house.

  5. At a friend’s house, suddenly there was a large fan noise. I asked him what kind of ac that he had. He flipped a switch in the kitchen next to me and the whole thing went off with a huge bang that startled me. It seems that attic fans have louvers that shut the attic off from the living part of the house when the fan is not running. Did you put something in to close the hole in the hall ceiling when the fan is not running? Or, did he just have something unusual. I know absolutely nothing about these since I only know one other person who has it. That person just sucks hot, humid air from the outside to the inside…not very comfortable and definitely not cooling at all. It does not roar or bang when it is turned off.

    I thought I would marry that guy with the banging attic fan. I think I would have broken that fan with the horrendous roar and banging.

    When I first married, my parents gave us a window fan that sucked air out of the house. We just opened the windows a bit on the other end of the house. It really did cool the house, taking stifling air out of the house. The breeze it caused allowed for my body to do its job of cooling me.

  6. We often talked about doing this when we lived in the Southwest. Now as wimpy Northwesterners “suffering” through several days hovering around 80 degrees (!!!) the idea has surfaced again. This post was good timing to remind us of it.

  7. We installed 3 of the QuietCool fans. We put the lower cfm model in the upstairs bedrooms and run them all night in the summer. The larger cfm fans go in the hallway. Very quiet for sure!

  8. Nice job! How did you mount/affix the fan to the plywood? Did you use any insulation strips on the plywood/1×4 surface to minimize vibration?

    • Hey Rick, I removed half of the caging around the fan and simply attached it with screws to a new attic door using the caging. Insulation strips might be a good idea–it’s pretty noisy–but I’m not sure how much it would reduce that noise.

  9. Do you have ceiling fans? You would also need them to survive the heat in a non air-conditioned space!

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