DIY Exhaust Fan for your Shop
George VondriskaDescription
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.
Air Movement
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.
The Concept
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.
The Build
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.
We’re here to help
Are you a fan of the fan? If so, we have more shop tips to help you out. Have a look!
In my old shop, I had an exhaust fan, a whole house fan in the ceiling, and I loved it. First thing in the morning in the summertime I would turn that on, open windows. They'd pull all the cool air in from the outside. If I was doing anything that was stinky I could turn that fan on, and it would pull all the air out of my shop. I don't have that here. So I made this. This is my shop-made exhaust fan. So here's what I've got going. Three box fans right off the shelf from a big box store. They're 20 inch box fans. What I did is I built a plywood frame, and the plywood frame is divided into squares that receive each fan. So it's kind of like a bookshelf with really big spacing between the shelves. Now, if you're going to do this in your shop your mileage may vary. You're going to have to adapt this to whatever your setup is. I've got a three foot wide door out here. So because I had 20-inch box fans, the plywood frame was only a little over 20 inches wide. To cover the difference, I added hardboard to the front. Masonite. What that does is it acts as a flange, then, that goes up against my doorway. Obviously the whole thing's on casters. So when I do this, No, no, no, no, no, no, no, no no, no, no, no, no, no, no, no. Like that it closes, it kind of portholes up against my door opening and seals it up in there. And then of course it's on casters so that when I'm not using it, I can do just the opposite. Get out there, close the door take care of it. To turn everything on, I use a multi strip because I'm way too lazy, you know, to turn three fans on individually, I'll talk about that. That's something I would do differently. I put a multi strip on it. All three fans are plugged into that multi strip. So outbound, I only need one plug instead of three. When I want to turn it on and off I flick one switch, not three. Now, if I did this differently that tippiness is the only thing I don't like about this. Because it mostly just lives here up against the doorway, it's not an issue for me. But if for some reason I was compelled to move this around the shop, it needs something so that it's not so forward heavy. So it doesn't tip forward so much. But for me, the typical application is it's in the opening. And what I do is I turn this on and then I open doors or windows on the other side of the shop and it moves air across. And then at the end of the day, when I'm done with it, all I really do is pivot it back like this. That corner is staying against the door frame. So the tippiness, it really isn't an issue for me. Overall works great. I just leave 'em at high speed all the time and have never so far had a reason to feel like I need to slow 'em down. So this thing has worked great for me. Maybe it'll work great for you. Take advantage of a service door opening in your shop like I have here in order to get air moving through, keep you cool and help exhaust out fumes and dust and other stuff.
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?
Would this system work better as a way of getting saw dust out of the air than a system that uses a filter?
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.
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.
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.
Why leave open space around fans, would not the fans pull better if the space around fans were closed up
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.