Affordable DIY Window Insulation
February 21, 2005 9:40 AM   Subscribe

The windows in my flat do a lousy job of keeping heat in and cold out. Is there a way to improve the insulating properties of window glass without installing double glazing? Ideally it would be something I could install myself (and if necessary remove when I move out of my rented flat.) Googling turned up various window films, both do-it-yourself and have-somebody-do-it-for-you. Any experience with these or similar products? Any other suggestions?
posted by yankeefog to Home & Garden (12 answers total) 2 users marked this as a favorite
Similar to what you linked, there's also a DIY winter-only plastic option. Imagine using double-sided tape to put giant sheets of plasticwrap over the whole window, and shrinking it to fit with a hairdryer.

Cheap, easy, and temporary. Only downfall is that you can't open the windows while it is in place.
posted by Kellydamnit at 9:59 AM on February 21, 2005

Have you thought about installing cellular blinds over the windows? They're also called honeycomb blinds and can have one, two or three layers of cells. They are much more insulating than regular venetian blinds because they trap air within the blind, forming a nice barrier between the window and your room. We use these blinds at our house and it's quite surprising just how effective even the single layer is.
posted by onhazier at 10:09 AM on February 21, 2005

We used to used what kellydamnit describes. Worked great. If you have kitties, you might want to use masking tape lines to make it clear to them that there is something there. Alternately, you can watch them try to jump on your windowsills only to bounce off the plastic.
posted by stray at 10:13 AM on February 21, 2005

Best answer: I'm sitting in a home office with windows that are insulated by exactly the same kind of system Kd described. You can get this stuff at just about any decent hardware store, I think, and it's basically a big roll of what looks like Saran Wrap, and another small roll of double-sided clear tape. You use the tape to mount the film across the inside of the window, and then run a blow-dryer across the film to shrink and tighten it.

If you do it carefully, you really don't even notice the plastic, since you can get it pretty taut and smooth. (It takes a couple of windows to get a feel for how to use it, though, so start on some windows where you don't care so much if there are wrinkles.)

The main thing I found is that while you have to be careful not to melt a hole in the plastic with the dryer, you've got to keep the dryer very close to the film, or it'll take _forever_ to tighten up. What I found works best is to keep the front edge of the dryer snout actually touching the plastic, but with the dryer held sideways to the film, so it's not blowing directly at it but across it. You have to be very careful, and move the dryer up and down constantly, but it's the quickest way, and it gets the plastic very tight and clear.

Generally, that sort of system is going to work better than anything inexpensive you can apply directly _to_ the window glass, since it traps an additional layer of air between the film and the glass, and that's a big part of the additional benefit. Anything you could apply right to the glass has got to do all the insulating on its own.
posted by LairBob at 10:14 AM on February 21, 2005

Best answer: 3M Company Indoor Window Insulation Kit - $21.27 at
posted by ericb at 10:24 AM on February 21, 2005

Note that all these films work best if there's trapped air between the window and the film. If the window is really leaky, the films don't work, since the air moves enough to convect heat across.

Also, if you're leaking around the frame, the window film won't stop it.

So -- a bit a caulk, properly applied to seal up the window and frame can help, if this is the problem.

If the cold is simply the glass conducting heat, then the windows films are a big win.

Finally, if your cats have claws, err, umm, you know, I really don't have a great answer for that yet.
posted by eriko at 10:33 AM on February 21, 2005

Best answer: I use the same system that everyone else is talking about and I've found that the process speeds up considerably if you use a heat gun [like for paint stripping] and keep it moving it takes no time at all. Combining that with some nice insulated curtains [close them when the sun goes down, and open them when the some comes up for best heat management] which you can buy or make yourself. I've fought with beastly winters and I've found that window glazing shows up pretty low on my list after doing simpler things that also make a big difference: window putty in cracks where the window doesn't close right, insulating outlets and switches elsewhere in the house and caulking around the outsides of the windows [where the window meets the wall] both inside and outside. This pamplet outlines other ways to insulate up windows in ways that are a bit more high tech that disposable plastic, but I always buy the cheapest window film at the hardware store and it works pretty well for me.
posted by jessamyn at 10:42 AM on February 21, 2005 [2 favorites]

Buying a $20 heat-sealed plastic kit for each window can be expensive and may not be necessary, in my experience. I bought bulk clear plastic sheeting and taped it over the windows of an old drafty cabin I was living in, and couldn't believe the immediate difference in retained heat. The next year, I also stapled sheeting *outside* the windows, including the frame, which was also leaking. It was dramatically warmer all winter.

You lose a bit more light and clarity through the window, but generic sheeting works well if you're on a budget. No hair dryer required, either.
posted by mediareport at 11:44 AM on February 21, 2005

Be aware that the double-sided sticky tape is a bear to get off the sills, especially a few years later when it has dried up and yellowed.
posted by five fresh fish at 12:04 PM on February 21, 2005

If there are drafts, you can stuff plastic shopping bags in the gaps with a butter knife, looks like hell but does the job. If you have any windows that you don't need as windows (north side with a bad view or something), you can get a sheet of styrofoam insulation, cut it to fit and tape it in the inside of the window sill.
posted by 445supermag at 12:19 PM on February 21, 2005

I live in a drafty, rented apartment, too, and have remedied it rather well by using two things. In addition to using the window-film stuff, I bought a removal silicone sealant from Home Depot. (I looked around on their website but couldn't find it; still, any decent hardware store will know what you're talking about if you say you want some removable sealant.) I have not yet peeled the stuff out of the seams in the windows -- to which I applied it liberally -- but I can say that the sealant, in combination with the film, definitely cut down on the draftiness of my apartment. In fact, there's no draft at all anymore.

I have the stuff at home and can check the name of the product for you later. Just email me if you'd like me to do that.
posted by Dr. Wu at 1:42 PM on February 21, 2005

Response by poster: Thanks, all! Your answers were extremely helpful. After reading them, I went to my local Homebase and bought the product several of you described; the brand I bought was Stormguard Double Glazing Film". It cost £6.99 (about $13) for a 4'6" x 3'0" sheet of it, and that was plenty to cover my window with a fair amount left over. I've just installed it tonight, but so far, it seems to be doing a top-notch job of keeping out the cold. It doesn't look incredibly elegant, but it doesn't look bad, either--you can tell there's a piece of plastic stretched over the window if you look, but it won't necessarily catch your eye if you aren't looking right at it.

I only wish I had known about it earlier in the season--I could have prevented a lot of drafty necks. (Well, really just one drafty neck, but on a number of occasions.)

Thanks again.
posted by yankeefog at 11:00 AM on March 5, 2005

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