Advice on installing an air conditioner into a window sleeve that's too big?

June 25, 2010 8:17 PM

In the apartment I'm moving into, each room has a wall sleeve (just below the window) for an air conditioner. We tried installing one of my air conditioners in there tonight, and it's too small to fit the space. It mostly fills it, but even with the fins on either side of the air conditioner pulled out, there are still spaces above and below. Does anyone have any advice on how to properly install the air conditioner?

Just a bit more information: the air conditioner is probably meant to be installed in a window, and the landlord told us that it wouldn't be a problem.

posted by gchucky to home & garden (11 answers total)

You can always fill the gaps with styrafoam. It comes in 3/4", 1", and 2" thick panels at any home improvement store. It's really cheap and will do the job fine.
posted by sanka at 8:25 PM on June 25, 2010

You can also get the thick foam tape that has adhesive on one side. Get a half inch thicker than the space you're insulating and stick it around the side. When you put it in it will compress a bit and give you a tight fit.
posted by msbutah at 8:55 PM on June 25, 2010

What you need is foam-a-fill
or any brand of expanding foam, window sealant.

This is what contractors use to fill gaps in windows, doors, AC systems. This stuff will close the seal in 100%.

But if you have never used this stuff, practice first. seriously. it expands A LOT. get a feel for it. If you get it on clothes or carpet, it ain't never coming out. It will take two weeks to come off your fingers if you get some on you (and you probably will get some on you.)

Also, use painters blue tape to close off any entrances into the inner workings of your AC unit. You do not want the foam getting inside the AC unit, that would be very bad for the AC. Only tape off what you need to tape off, to protect the AC unit and to still let it vent. Your AC needs to be able to breathe.
posted by Flood at 9:10 PM on June 25, 2010

I stuffed crumpled plastic carrier bags in the gap when I last had a poor fitting a/c sleeve. Worked well enough at the time.

(then again, I used crumpled plastic carrier bags to fill the gaps in the windows, too)
posted by devbrain at 9:14 PM on June 25, 2010

One other note, each can of foam-a-fill is single use. Once you tap the can, you need to use the whole thing right then. So, you might need to actually get three cans. The first can, practice with it outside. Then, if you are good, you seal the AC with one can, but you might need that extra can too.
posted by Flood at 9:14 PM on June 25, 2010

If you go to Menards (and I assume the rest of the places) and look for the aisle where they have door sweeps and garage door bottom seals, there should be all kinds of foam filler material designed specifically for this.

If you use the foam in a can sealer, be prepared for it to make a giant mess. It works, but it is sticky. I'd wrap the AC in a plastic bag and then cut the bag off after the stuff cures. Also be prepared to have to dig the ac unit out if you want to take it with you.
posted by gjc at 5:21 AM on June 26, 2010

You could always just duct tape the gaps away.
posted by astapasta24 at 6:10 AM on June 26, 2010

I strongly disrecommend the Great Stuff foam sealant in this case (and many, many other cases.)

Duct tape and styrofoam will do just fine, just keep the bugs and birds out and the cold air in. If you want to get classy, cut a front out of cardboard and paint it the color of the room. Make sure the AC can drain outside and not inside and make sure the back of the ac can breathe.
posted by mearls at 7:00 AM on June 26, 2010 [1 favorite]

I agree with mearls. Foam sealant is easy to apply, but you or someone will regret it later when you need to remove the air conditioner, because it will pain to clean up. I'd go buy a sheet of pink (sometimes blue or white) insulating foam at your local home improvement store and use that to fill your gaps. It is inexpensive, it comes in different thicknesses and you can easily cut it with a utility knife.

Any leftover gaps can be sealed with duct tape or a number of other materials.
posted by 14580 at 7:27 AM on June 26, 2010

Are you sure that the a/c unit is large enough for the room? Right now, I'm dealing with a too-small a/c unit in my living room, which is going to kill me on my electric bill. Perhaps the answer here, if your finances can handle it, is to get a larger a/c unit - one that fills the sleeve more than the current one.

Then again, if the a/c unit is the correct size for the room, the pink insulation board and duct tape sounds like the best idea.
posted by LOLAttorney2009 at 7:41 AM on June 26, 2010

The sleeves are designed to accomodate specific models of ACs -- often Fedders. The models aren't cheap but are often higher in cooling power and efficiency than non-sleeve window units. If you are staying in the aprtment for more than a single summer it might pay off to get the right AC and Craigslist your current window unit. Also, some window units work terribly or not at all in sleeves because they vent or radiate on their tops or sides, which is fine if sitting exposed in a window frame but noy if enclosed in a metal wall sleeve.
posted by MattD at 8:22 AM on June 26, 2010 [1 favorite]