The perfect solution for a bug-proof AC is a mini-split (pictured below) where the condenser and evaporator are completely separate and connected by only refrigerant lines. The problem with mini splits is cost, where I live in Canada a 1-ton (12,000 BTU) mini split is $2,000 and cannot be sold to the general public while a 1-ton window AC can be had brand new for under $450.

Items Needed
- Silicone
- Caulking Gun
- Double Sided Tape
- Diatomaceous Earth
- Window AC Unit (I like Toshiba and LG smart models since they can be controlled via WiFi)
Bug Proofing a Window AC
Today’s Window AC units are designed well, but they still are not completely bug proof. The best way to ensure bugs don’t get in to your grow room is to take the AC apart and carefully seal any gaps with silcone and line the bottom with double sided tape that’s covered with diatomaceous earth a natural pest blocker that shreds the soft bodies of aphids and mites. This may seem like overkill but bug proofing a window AC turns essentially turns it into a cheap affordable mini split. And trust me this is much easier than battling a pest infestation down the road.

Apply the diatomaceous earth in any areas where bugs may want to crawl towards the front of the AC. Use the two sided tape to make strips (a bucket helps). Wear an N95 mask while working with this stuff, it can cause mild respiratory irritation if inhaled in large amounts. Don’t use any diatomaceous earth in the front portion of the AC. You don’t want the powder getting blown into you grow room.
Fill any gaps that may allow bugs to crawl into the indoor portion of the AC (front). The Toshiba AC I bought was sealed fairly well, but there were still a few big gaps around the circuit board that required silicone. Silicone holds up better to drying and cracking so I recommend it over stuff like Alex+ Caulk which is better suited for sealing the plywood sheet to the wall (see below).
Congrats you have sealed your window AC so that it can function more like a bug-proof Mini Split, at a fraction of the cost.
Installing an Air Conditioner in a Grow Room
If you are using a window air conditioner and not a mini-split you should take care to fully seal the AC into the window to prevent bugs from entering from the sides as well.
Start by building a wooden frame for the AC to sit on. This will give you something to apply caulking to.
Insulate the window using styrofoam. A jigsaw will give you a cleaner cut than trying to use a knife.
Cut a piece of plywood to fit over the window, with a cutout for the AC. This will allow you to seal the AC with a seam of tape as a final line of defence. Caulk the plywood to the wall.
UPDATE: I received an alert (from my Pulse Pro) that my flower room from had a light leak. It turns out the styrofoam used for the air vent lets light through. This turned out to be an issue because I run my night cycle during the day to conserve electricity.

This was easily fixed with a quick coat of black spray paint. Since I already had plants in here having an exhaust fan came in handy for venting the spray paint fumes.
