The two things every grow room needs are an air intake (to draw in fresh air with normal atmospheric levels of CO2) and air exhaust (to vent out hot oxygen-rich air). My grow room has two windows which allow me to use one as an air intake, and the other as an air exhaust. Windows are great to use for intake/exhaust because it does not involve any major work like drilling 4″ or 6″ exhaust holes through concrete or brick. If there was no window for the air intake I would have put it on the door as the room is framed with concrete.
Materials Needed
- Furnace Filter (I use 16″x25″x1″, MERV 11+)
- 6″ Flange
- 6″ Exhaust Ducting
- 2″ screws
- Alex+ Caulk or Silicone
- Foil Tape
- Black Spray Paint
- Plywood Sheet(48″x48″ is typically enough)
Tools
Air Intake
For the air intake I started with a window where I installed blinds for privacy.
Next find a piece of plywood large enough to cover the window. Cut out a hole that is 1″ smaller than the size of your furnace filter. See my related article on Cannabis Air Intake Filters, and why I use furnace filters.
Drill the corners out using a drill and cut the wood out. Ideally use a jigsaw but you can also use the Milwaukee one-handed hackzall, making it another reason why it’s the favourite tool I own.
You can see the 1″ overhang which will keep the filter in place. Next you use 1″ thick wood on 3 sides of the hold to act as a border. Use thicker wood if you are using thicker filters, I use 16″ x 15″ x 1″ because they are the most common and the ones Amazon/Costco sell for cheap.
Glue these pieces down but do not drill them in yet. Once you have your 1″ thick pieces framing a 3 sided border you are ready to put overlapping plywood overtop. Cut it so it is 1″ overhanging, just like the initial piece.
You are creating a sandwich for the furnace filter so you can easily slide a new filter in when it is time to replace.
Air Exhaust
The air exhaust is much simpler to make. You essentially just need to seal the window and install a flange for the air duct. Start with blinds once again for privacy and aesthetics. Blinds look much better than boarded up windows, even in the era of legal growing aesthetics and stealth should be a consideration.
I am using a 6″ fan so I found this 6″ flange adapter at the hardware store. 6″ exhaust tubing fits on one end while the other end can be screwed directly into wood.
I recommenced using at least 3/4″ thick plywood for any outside windows to provide additional insulation. I did not have any thick plywood around so I glued some scraps together.
Add a line of silicone or Alex+ to seal the gasket before screwing it in. These gaskets are usually round but I happened to have this square one kicking around.
I gave mine a fresh coat of paint. Wood is an organic substance so I like to seal any exposed wood with paint, even though it is going to be resting behind a tent in my case.
Windows are typically framed with wood, so you will have studs that you can drill the board into. Use long wood screws. The ones I used were 2″ deck screws.
Push the tent up against the air vent. This will show you exactly where you need to cut into the tent. Use a utility knife to cut it up like a pizza for a tight fit with minimal damage to the tent. In the future, this can always be patched up with foil tape, which I also used to seal the connection between the tent, air vent, and 6″ ducting.
I spray-painted the inside of the reflecting ducting to further prevent light leaks outside. Even though this is a legal grow stealth is always top of mind.
The nice thing about the plywood sheet over the window is you have a sturdy surface you can screw your fan to. I also plan to attach my airpump here so it is raised above my water reservoirs.
Add a bend into the exhaust ducting to help further block light from lighting up your outside window.
That is it, you are done converting your window into an air intake/exhaust. For options on how to control your fan see the Ventilation page where fan dimmers and temp controllers are discussed.
