House Hacking: Garage Vent Fans, Thermostat Controlled

This project was brought about through an effort to reduce overall HVAC use during the summer; and the fact that no off the shelf product was available at the time of writing. Summer is in full swing here in San Diego, and with temps in the upper 80’s, the garage is a hot place to be with two vehicles parked inside at the end of the day. This in of itself isn’t bad; it becomes an issue when you have living space above said garage with two hot vehicles radiating heat into the walls and ceiling, thus adding to the heat mass that the A/C must work to cool off.
TL;DR- we take $125 in supplies and make something.
The above product is what we were looking for, but with a thermostat instead of a humidistat. We don’t have humidity here 😉 The cost at the time we first came across the product was $149 a piece, we need two. (It is listed at $119 as of 7/29/16.) This is on the pricey side for a product that doesn’t meet our needs out of the box. What to do?
A few sessions of searching later, this thermostat controller was consistently popping up on the list of items folks purchased. For $17, how could one go wrong? We found the brain of this project, now to plan out the rest of the needed items. This controller runs on 120v AC, so we will be looking for these types of parts versus 12v DC.
We installed this brand of fan to vent our server closet in our office here at 1850 Realty. Well, a couple of them with a thermostat that runs on USB power at 5v. This 120v model is rated at 110 cubic feet per minute of airflow, and is about the right diameter to work with the vent openings we have in our garage. We added four of these to our cart.
We needed something to house our thermostat and outlets, and found this handy dandy box. This with a few more sundries and our project was ready to begin.
One of our two vents- not much airflow with the louvers and pest screen. These measure 14 inches by 4.5 inches. We couldn’t find any registers readily available, so we will fabricate from square one.
Fast forward to a time when our supplies have arrived and a trip to the hardware store has been done as well. We procure some appropriate gauge sheet metal, and begin scoring lines for our vent plates to trim in the metal brake. A metal score tool etches like butter in this mild steel. We opt to have one inch overlap in all directions, for an overall size of 16×6.5 inches.
We line up our first of three cuts, this is an “easy” project so far!
After all of our cuts are made, I notice some blotches appearing here and there. Sheet metal is fu&%ing sharp, one of my fingers was cut and I didn’t even feel it. After cleaning up this mess, it is time to continue.
The next step was to measure our mounting points for the registers to the wall. Some work with a combination square found points on a diagonal from all four corners for a professional looking product. After drilling these, it is time to center our fans and get ready to cut the vents for them.

Our fans measure 4 11/16 inches in diameter, so we need to cut a radius to match this. Luckily we have a radius jig for the plasma cutter! We measure everything multiple times, and cut once. Our video above shows just how fast and easy it can be.
Both plates have been cut out, next up is to place the fans and mark our mounting points.
This was one of the most tedious parts of the project- centering and squaring all four fans. Holes punched and drilled.
A few coats of lightly textured off white spray paint wrap up this phase of fabrication.
Back to the electrical side. We have an accessory cord, some outlets and a switch to bypass the thermostat if you want to use the fans to vent during a garage project. We couldn’t find a timer at our local store, and realize that would be a great way to run the system and have it turn off automatically. We will likely add this feature in at a later date. After a little jigsaw fitting, we decide on a configuration.
We mark all of our cuts, and drill access holes to use our pneumatic reciprocating saw to make easy work of the plastic.
We have succeeded in making one hell of a mess. Using a saw like this charges the plastic, and it sticks via static to everything :/
This just might work! We fit and install our outlets, switch and wiring.
It isn’t pretty at all. Leveling to install in line with our existing electrical fixtures.
Fans have been installed to both vents. We slipped cutting one hole, and you can see the error here. Our paint ran a bit as well. It gives this project some character from the start 🙂
We measured our electrical plugs for the fans, but were off 2 inches trying to line up our control box. We moved it up 5 inches to compensate. This is real life, not some fake Pinterest post.
Electrical is finished- the small wire stick up is the temperature sensor. We set the thermostat to cool to 80F, which should have it running for a few hours on a hot day. Testing will be done in a follow up post to see how we are actually doing.
We are up and running. We thought about having both vents pull air out of the garage, but we are sealed fairly well. We are using the bottom vent to push air in, and the top to pull air out. We will measure our power use- accounting for the load added here versus the run time reduction in our HVAC. Stay tuned for a follow up!
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