Whether you’re looking to keep the air in your shop a little fresher, or you just want to keep the air moving so you stay a little cooler in the warm months, this DIY exhaust fan is for you. It’s so simple to build; taking advantage of simple box fans you can get from any home center or big box store.
I don’t know how many CFM this unit moves, but I can tell you this. When all three fans are running on high and a window at the other end of my shop is open, I can feel A LOT of air pouring in. How many CFM in a lot? A bunch. 🙂 In other words, this simple system is really effective.
Here’s the idea. We’re going to stack three box fans vertically to fill the frame of a service door in your shop. The fans themselves won’t fill the door frame, so you’ll have to build a flange assembly that makes up the difference. The tighter you get the fit, the better this will work.
Your DIY exhaust fan will be idiosyncratic to your door, so we can’t give you dimensions or a specific plan. I used plywood for the frame that surrounds the fans, and hardboard to create the flange that goes up against the door opening. Start by buying the fans, and build the frame and flange to work with them. Casters on the bottom facilitate moving the unit into and out of the door opening.
Our DIY exhaust fan is designed to move air out of your shop, while pulling fresh air in. If you want to filter the air within your shop, check out our homemade air filtration system.
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I have something very similar (2 fans, 1 high 1 low) in my basement shop. Not having other windows or doors to open I have the bottom fan reversed and the top blowing out. Except for “extreme” temperature days it really helps. I am also blowing though a screen to keep out bugs.
What if you only have a door in the basement and a window but they are in the same exterior wall, and not other windows for cross ventilation? would this work too?
It would not be ideal but it would likely help to some extent.
Woodworkers Guild of America
Would this system work better as a way of getting saw dust out of the air than a system that uses a filter?
Hi Heath. You need to use a filter with this system. Yes, it’s a great way to pull dust out of the air. It should serve as a complement to and not a replacement for a dust collector that captures dust at the source.
Paul-Woodworkers Guild of America
the tippiness would also bug me. Simple fix would be a 3x8x16 solid concrete block on a the shelf of the bottom frame for ballast. I do this with my portable bench saw (table saw) set on a workmate base to keep it from tipping during use. Works great. about 16# per block. one would do I imagine.
The fans would work better if you close the gaps between them and between the frame and the floor. Air takes the path of least resistance, so some air is likely currently sucking in between them and going right back out without ventilating the shop. Close the gaps and you may find you don’t need as many fans.I won’t comment about the dust issues around these non-explosion-proof motors.
I wondered about the non explosion proof fans too. Not sure how critical that might be in the way he is using this set up. A discussion about that seems warranted. I would benefit from knowing more.
One way to eliminate the tipping from the front-heavy stand might be to move the plywood frame etc. further in on the castor foundation. If the thresh hold is to high for the castors, one set could be moved toward the center (back set) and the base could be tapered to actually cantilever the weight by the base extending over the thresh hold. I think that would solve the problem. Excellent way to ventilate an entire shop in hot weather
Nice economical idea but some sort of screening might also be advisable to keep out bugs and critters.
I used it all of last summer and bugs weren’t a problem, at least where I am. But if they’re heavy in your area, a screen would be a good idea.
George, Appears that you may have room to hinge the unit to either door jam, this would eliminate the chance of the unit tipping over. Can always pull the hinge pins to move the unit.
I thought about creating a pivot point, but I also like the idea that I can roll it around the shop if I just want to create a breeze. Maybe a pivot with easily removable pins…..
Why leave open space around fans, would not the fans pull better if the space around fans were closed up
Hi Paul. I’ve never tried doing that, so I’m not sure. It’s not clear what the benefit would be, but if you feel that there is an advantage, give it a try and let us know how it works.
So what do you do in the winter? Are you moving cold outside air through your shop? It seems to work against the heating you need.
Hi David. The fans aren’t running constantly; only in situations where a lot of dust is generated in an area that cannot be captured by George’s dust collection system. In those situations he will run this setup for short periods of time in the winter. In the summer he is more apt to run it for longer periods of time, as it also adds a nice cross breeze to the shop which is great for comfort.