How can I insulate my window air conditioner against the cold?
January 15, 2016 10:38 AM   Subscribe

The sides are essentially open to the elements and I'm looking for a way to cover them up.

I have a large, heavy window air conditioner in my rental apartment that I can't remove from the window for building reasons. The side accordion panels as well as the frame that would hold those panels in the window are gone so I essentially have an air conditioner in the window with 6-8 inches open to the cold winter air on either side.

I've tried this foam insulation and it doesn't seem to work. These plastic panels won't stay because the frame for the panels is missing. I believe I would have to remove the A/C unit to use something like this, but it's too heavy and complicated to move.

Can you recommend a product or an easy hardware store solution to cover up the sides of the A/C from the elements?
posted by annabellee to Home & Garden (12 answers total) 1 user marked this as a favorite
Is appearance or damage to the wall a concern?
If not, I recommend the handyman's secret weapon.
posted by FallowKing at 10:50 AM on January 15, 2016

I am reading your question as if you are want to stop the cold coming in from the gaps in the window and through the air conditioner itself, and are not trying to protect the air conditioner itself from getting cold.

I would probably do 2 things in that situation. First I would cut some plywood to close the openings on the sides of the window and either attach it with some small nails or strong tape. You could then use expanding foam insulation like "Great Stuff" to make sure there are no gaps for air to go through. If that is enough to make things fine then that's where I'd leave it.

If it was still too cold then I would make a plywood box to cover the whole thing, air conditioner and section of the window, give it some basic legs to support itself and then put a sheet or table cloth on top so it wouldn't look too hideous. A handier person could probably turn it into a table or shelf.
posted by any portmanteau in a storm at 10:52 AM on January 15, 2016

I have used actual pieces of egg crate foam (like, the cheap mattress pad egg crate, you may want to use 2-4 layers of it since it's thin) or you can buy a little bit thicker nicer upholstery foam at a fabric store. I make a pad just bigger enough than the space that it will wedge itself into the window frame and against the A/C, though you can use popsicle stick tabs or duct tape or other methods to make it hold more firmly. It's basically a custom-sized pillow.

To make it nice, you can wrap those foam pieces in fabric, pillowcases, cut down bits of old sheet or t-shirts etc.

You could, if you really want to make it fancy, secure the foam pad to the plastic accordion with heavy double-stick tape or glue or something.
posted by Lyn Never at 10:53 AM on January 15, 2016

This isn't super high tech, but here is my approach. You really have to cover up the entire AC unit to keep the cold out, by the way. Even if the panels are totally insulated, cold air comes in through the unit itself.

In your case, I would tape in some cardboard into the gaps. Then I cover up the entire area (AC unit and all) by taping a heavy duty plastic bag to the window frame. Next I roll up some old towels and press them around the top, sides and bottom of the unit, taping them as needed. Then I take one more big towel and cover up the whole area again, taping or stapling (if that kind of damage isn't a worry) it to the window frame. If you want to pretty it up, you can do a layer of fabric or something over the whole thing.
posted by kimdog at 10:53 AM on January 15, 2016 [1 favorite]

Oh yeah, you also need one of these or, if you're my mom, an old bedspread and some clothesline rope.
posted by Lyn Never at 10:58 AM on January 15, 2016 [1 favorite]

I think you should take old clothes you don't care about or rags and stuff the holes full of them, use something like kimdog's plastic bag solution to make sure air can't flow through at all (you can buy saran-wrap-type stuff at hardware stores for this too), then put a low shelf or similar in front of the window and pile cardboard boxes full of bedding or clothes as a sort of insulating wall in front of the window, maybe with another layer of plastic for good measure.
posted by XMLicious at 11:00 AM on January 15, 2016

Instead of stuffing the area with cardboard and rags, how about building a box around the whole situation using a piece of rigid foam insulation?

Then you can seal it to the window with duct tape, or (my recommendation), 3M heavy weathersealing tape. The tape will not leave as much damage behind it like duct tape will.
posted by JoeZydeco at 11:05 AM on January 15, 2016 [2 favorites]

I use heavy-duty plastic wrap that I begged off the art handlers at work and tape it over the entire rectangle of window occupied by the a/c. I use painter's tape so it doesn't leave gack behind on the walls and window frame. The only issue I have with this is that it rattles in an irritating way when the wind is blowing a lot and it sounds like a pet sneaking into the trash and I am immediately on high alert.
posted by poffin boffin at 11:28 AM on January 15, 2016

I would just use one of these plastic shrinkwrap weathersealing things over the whole window (select the size that would fit your window+ac opening).
posted by melissasaurus at 11:32 AM on January 15, 2016

I think you should try and come up with a solution that works for the summer as well. You were losing a lot of the a/c efficacy by having an essentially open window all summer long too.
posted by srboisvert at 1:06 PM on January 15, 2016

FWIW, when I had to deal with this problem while living in student-grade housing during college, I just overlapped duct tape across the openings until they were sealed. It worked out surprisingly well insulation-wise, and I didn't have to do anything to maintain it for the entire year that I lived there. If you have more funds and time, one of the weather sealing solutions offered here is probably better, though.
posted by indubitable at 3:24 AM on January 16, 2016

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