Warm up basement apartment by insulating (covering) single-pane windows
December 22, 2021 12:56 AM   Subscribe

I recently moved into a basement apartment that has five single-pane windows. I’m looking for the best cheap way to cover the windows with some sort of rigid insulating material to stop the loss of heat from the room. I have an idea, but would appreciate any constructive suggestions/insulating experience.

So, I recently moved into a basement apartment that has five single-pane windows.

Now that winter has come, it's getting a bit nippy.

Along the long Eastern wall of the room, there are three large portrait-oriented windows
(each of which can be opened outward like two barn doors).

On each end of the long room, there are smaller non-opening landscape-oriented windows high in the walls
(like, if you had a big bed frame set against either of those walls, you would still see the window atop the head of the bed frame).

[Images of the windows can be seen here]

As it is an old house, all of the windows have single pane glass. Because of these windows, any heat that the room receives almost instantly disappears (especially at night when it’s close to freezing outside). If I stand next to any of the windows, I can definitely feel the coldness coming off of them.

I’m looking for a cheap way to cover the windows with some sort of rigid insulating material,
like R-Tech rigid foam insulation or Owens Corning Foamular foam board, or something similar.

As the windows are inset a couple of inches, I was thinking I could put a rectangle of rigid foam insulation (with some squishy foam wrapped around the rigid edges to keep it held in place) in the inset “frame” between the room and the windows themselves.

I am not really worried about cutting off the outside light as I have plenty of lamps—but I would like to be able to easily take the insulating panels out when needed (and so hopefully using them without any need for hardware or tape holding them in place).
I figured I would attach two handles or cupboard knobs to the room-facing side of each panel so I could easily lift them in and out.

The insulation pieces don’t have to make an exact airtight seal, but I figured that an insulating panel that kept 95% of the room’s air from directly contacting the cold glass would definitely have a positive effect on room’s heat retention.

I thought if I got a couple of 8' × 4' × 1" (or 1.5") pieces of rigid insulation, I could cut them to fit into each of the window frames, and then add a squishy edging of foam pipe insulation to each one so that they would hold in place.

Any one out there done something similar, and/or can recommend a better solution?

(The standard “cover the window with plastic, and fit it with a hairdryer” method seems like it wouldn't work on these windows as there’s not really a good place to anchor it, and I don’t want to have to put in any nails/staples/tape. Also, I don't want normal bubble-wrap as the R-value is like 1 as opposed to the 5–7 seen with the rigid foams)
posted by blueberry to Home & Garden (11 answers total)
The plastic and hair dryer approach is definitely where you should start. It usually works with double sided tape which you run around the perimeter casing. Even if you also add foam, this will help control air leakage and provide improvement when you remove the foam. Weatherization kits are very affordable relative to other measures.

Personally, I’d stop there. Natural light is important. But, cutting foam to fit securely in a window can work. You can also hang heavy cloth over a window to reduce discomfort and at the same time gain some privacy.
posted by meinvt at 1:05 AM on December 22, 2021 [6 favorites]

The plastic wrap will definitely work on these windows and it has a really marked effect. Surprisingly so. Heavy curtains are also the traditional option.

I've also seen the foam board approach work too so your plan isn't unreasonable at all.
posted by knapah at 1:31 AM on December 22, 2021 [1 favorite]

Looking at the images, you have the shades and the shade hardware in there which may interfere with getting the rigid foam panels seated in the windows. To get a good fit, you might have to unscrew the shade mounts. Is that worth the effort/possible in a rental?

Really, the hairdryer stuff works great. I used it for several winters with fullsize sliding doors. The issue you have here is that if you put the double sided tape around the molding, you won't be able to adjust the shade. So, pick a shade height and seal it up with the hairdryer and see. They are cheap and easy and worth a try first.

The other issue that neither the rigid foam nor the shrink plastic will address is possible gaps around the outside edges of those window moldings. They can leak like crazy sometimes.
posted by Gotanda at 3:24 AM on December 22, 2021 [1 favorite]

My parents used to have a basement guest room with windows like you describe (the picture didn’t work for me though). We used to just shove a pillow in each. They usually kind of morph to the right shape, block the light (which was good for sleeping in) and really did a lot for drafts. Obviously it was also very easily removable.

Someone else will answer better, but there may be moisture implications of using the rigid foam.

Good luck!
posted by raccoon409 at 4:22 AM on December 22, 2021 [1 favorite]

Best answer: Imgur isn't loading for me for whatever reason but quite a few years ago I had the wallet sucking condo of old drafty apartment + central heating and the unfortunate additional complication of severe underemployment. I invested in some extruded polystyrene sheets cut to window size and did exactly what you're proposing. (Protip, measure your windows. Home Depot will cut your foam to size for you.) They let some light in, and it was warm pink toned from the foam, so it felt like I was living in a womb all winter.

Anyway my heating bill was so low that my landlady was pretty sure something had either broken or I was sitting frozen in my living room like Jack Nicholson and actually called to check on me.

tl;dr your plan will be extremely effective.
posted by phunniemee at 5:33 AM on December 22, 2021 [5 favorites]

Quickest thing to try: Bubble wrap.

Get some bubble wrap, large bubbles are the best, and something that will spray water. (You could probably use a damp cloth.)

Spray the windows with the water, and stick the bubble wrap -- bubble side to the glass -- to the window. The water will hold the bubble wrap there for the whole season.

Light come in, you get some privacy, and it's warm.
posted by mbarryf at 6:34 AM on December 22, 2021 [2 favorites]

Get the shrinkwrap plastic for windows that will stay covered, then bubblewrap. Bubblewrap on the outside and inside. Cut it larger than the window and tape it down; if you want to be able to remove it, tape magnets to the corners, and put magnets on the window frame; 1 side should be those business card magnets for easy alignment with a button-sized magnet.
posted by theora55 at 7:17 AM on December 22, 2021

I literally put saran wrap on my single pane windows and the entire apartment was warmer within an hour. You will be surprised by the effectiveness.
posted by panhopticon at 8:49 AM on December 22, 2021

You may have already thought of this or I may not be understanding your proposal correctly, but: if those windows are your second form of egress from the apartment, you don't want to be blocking them. At all.
posted by praemunire at 4:48 PM on December 22, 2021 [2 favorites]

The saran wrap type kits really do work. Also thermal insulating blinds or curtains would be a better option than a diy insulation thing and seems like the kind of thing that a landlord should be willing to do, especially if they're paying the utility bills. (In general, it seems that this house would be a good subject for a heat loss assessment, which is usually paid or subsidized by the utility company.)
posted by RandlePatrickMcMurphy at 7:17 AM on December 23, 2021

Response by poster: I ended up going with R Max 1" R-Matte Plus-3 polyisocyanurate foam insulation board, which has a R-value of 6.

I bought three 4' × 8' × 1" sheets at Home Depot.

Home Depot (at least the location I went to) will no longer cut rigid insulation for you, so I borrowed a tape measure and a metal L-square from another aisle and spent 20 or so minutes cutting the boards into the six custom window-sized pieces I needed. (I also wound up with a bunch of good-sized scraps which I am finding other uses for)

I bought two rolls of duct tape and when I got home, I edged each of the pieces with it—about an inch of tape on both sides and the 1" cut and uncut edges totally covered—so that there would never be any little pieces of foam falling off of the edges.

The foam board is foil-covered on both sides; a metallic side, which I faced towards the interior of the room, and the other side's foil has a bunch of big printed specifications and numbers, so I faced that side towards the outside.

Three of my windows can conceivably be seen by neighbors, so I covered the "ugly side" of those pieces with brown Kraft paper so the windows would look more presentable. (But again, it's a basement apartment, so the neighbors aren't even going to see my windows unless they go on their back deck and look over and downwards.)

Right now I have the pieces just kind of set in the window frames (not crammed in) so they're not a complete seal. But even so, last night was considerably warmer. I am plan to to pin a little piece of L-shaped plastic to the top of the three main windows that will then hang down and inch or two and gently hold the top in place.

I really noticed the heat difference in the small bathroom. Before it was always cold and I would usually have to turn on the ceiling sunlamp when I was in there. Turns out it was all because of the little window (in this bathroom window, I do have it really custom-fit crammed in there, with a couple parts half-carved out the foam to account for a latch and such, so the foam is really able to do it's job).

I know someone who once covered a big south-facing window of his solarium with rigid foam insulation and it got so hot (but probably not evenly or something) that it cracked the window. My windows all receive minimal sunlight filtered through evergreen trees, so excess heat is not a problem (also, the foam pieces will be removed and stored during the warm parts of the year).

Thank you to everyone for your suggestions, comments and especially your encouragement!
posted by blueberry at 8:23 PM on December 24, 2021 [1 favorite]

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