Temporary solutions for sealing my window air conditioner

May 3, 2018 4:46 PM

I have a window air conditioner. I rent. The windows are aluminum framed. There isn't a way for me to drill holes in the window to secure the accordion extensions so there's a small gap between them and the frame. I also see cracks where the extensions contact the unit. How do I best seal this up?

I know window A/Cs are just going to be leaky, but I'd like to minimize the leak. Should I use some kind of temporary sealant like this? Is there some magic way to apply foam strips that will help? Most of the instructions I see for applying them involve drilling the accordion and assume wood-framed window types that I don't have. In the past I've used duct tape, and that leaves a mess. What do people do to solve this problem?

posted by anonymous to Home & Garden (13 answers total)

Sheets of rigid foam, cut to size
posted by Caxton1476 at 4:49 PM on May 3, 2018 [1 favorite]

I just forget about the accordion extensions and fill up the space with soft stuff - towels and cardboard boxes if you’re making do, foam or actual foam insulation if you’re fancy. Bubble wrap is also good.
posted by mskyle at 4:50 PM on May 3, 2018 [2 favorites]

Response by poster: How do you secure those? The foam inserts, I mean.
posted by Anonymous at 4:50 PM on May 3, 2018

We use self stick insulating foam strips from the hardware store to augment the accordian panels. We stick it to the underside of the window, inside the sill and on the accordian panels themselves.
posted by sarajane at 4:56 PM on May 3, 2018

I had most of a roll of upholstery foam left over from something else last year, and cut pieces (measure carefully and then cut them slightly bigger, so they have some tension when you get them wedged in there) to fix these gaps. I actually used this in lieu of the accordions. Only thing I'd change for this year is wrapping them in cheap fabric or pieces of old sheet or even old t-shirts, because the foam yellowed and got a little sheddy and brittle where it was exposed to the sun on the outside of the window.

Obviously, this isn't secure in any way. If you're on the first floor this is probably a terrible idea.
posted by Lyn Never at 4:58 PM on May 3, 2018

Go to any hardware store and get some rope caulk. You can use it in one or two strips wide, and it's easily massaged. It's wicked cheap and should do the trick. It will also peel off later.
posted by Marie Mon Dieu at 4:59 PM on May 3, 2018 [2 favorites]

Spray foam sealant will expand to fill the gaps.
posted by Blue Jello Elf at 5:03 PM on May 3, 2018

Seconding rope caulk: easier to work with than seal'n'peel.
posted by holgate at 5:21 PM on May 3, 2018

You might also want to consider Duct Seal (note: PDF link). It is similar to but (in my experience) more sturdy than rope caulk. I bought it recently in the plumbing/HVAC section of Home Depot.
posted by forthright at 5:34 PM on May 3, 2018

What I did was take a 1x3 or 1x4 board and fit it into the window sliding slot just above the AC unit, so it provides a 3” tall wood piece running across the top of the AC. Screw the unit and the accordion pieces into the board. I used another piece to wedge the window down to keep it from opening.
posted by Huffy Puffy at 6:36 PM on May 3, 2018 [2 favorites]

When I’ve done the foam inserts I cut them slightly larger than they need to be and then just smoosh them in.
posted by mskyle at 6:46 PM on May 3, 2018 [1 favorite]

If you are talking a gap less than 1cm/.5 inch I'd just tape it over with some heavy duty duck tape like Gorilla Tape. You aren't going to lose significant cool thru conduction (especially on aluminum windows) but you want to seal the air gap to stop breezes, whistling and insects.
posted by Mitheral at 7:04 PM on May 3, 2018 [1 favorite]

Once I got everything in place I cut rectangular pieces of cardboard exactly the right size to fit over the accordion bits. So I wedge the cardboard rectangles in and they hold the extensions open to the full width of the window.

I had some spray glue handy when I did this and used it to cover the cardboard rectangles in aluminum foil so that they're waterproof, and they've lasted five or six summers so far.
posted by XMLicious at 9:05 PM on May 3, 2018