What I Know About Window Film Insulation

Our house is pretty chilly in winter, and it's quite clear that one of the weak links is the windows. You can tell from the avalanche of freezing cold air that rolls off the windows as soon as you open the blinds*. So this winter we decided to try that plastic wrap stuff that you tape around the windows and then blowdry to tighten it up and make it all smooth. It's kind of ghetto but we can't afford to replace the windows, so it will have to do, and I was determined to do it right -- there is a house nearby with plastic on the windows and they didn't prep it properly so the tape has come off and it's hanging down and it looks really ghetto.

There were two brands at the store, 3M and another brand from Quebec. This whole post would be much more useful if I remembered what the brand of the other stuff was; anyway, it comes in a blue box and it's from Quebec. We bought the two-window kit by 3M and the five-window kit from the other company; both kits were about $35, so you can see that the 3M stuff would have to be much better to be worth the extra money.

Here were the differences between the two products:

  • the 3M stuff had slightly wider double-sided tape, and the tape backing had red text printed on it - that doesn't seem like a big thing but our window frames are white so the white-only backing on the other tape made it a little harder to find the end of the tape. 3M advertise that "the difference is in the tape", and indeed that's one of the things they are known for, but apart from the slight difference in width and the backing, I couldn't perceive a difference in the tape. Maybe the other brand will start peeling off in February or something.
  • the instructions on the other stuff were more thorough. At first Blake interpreted that to mean that the other stuff was harder to install, but installation was identical for the two products, it's just that 3M tried to make it sound easy.
  • the non-3M film was thinner. I suppose that would make it more fragile but I didn't have trouble with it breaking, and it heat-shrunk better. I doubt the width of the film makes much difference to insulation; I expect insulation is mainly furnished by the air between the window and the film.

So this is what you do:

  1. Clean the window frame. I used a solution of water, dish soap and vinegar, and a cloth diaper. (I cleaned the window too because I'm not going to get at it for a few months.) Then I wiped it with rubbing alcohol - that's what the non-3M stuff said to do.
  2. Put the tape on the window frame. After the first couple of pieces I figured out that you need to peel a couple of inches off the backing paper before you put the tape up because it's really hard to start it when it's up on your window.
  3. Cut the plastic film to size. We ended up with lots of extra film, but I'm not sure how much extra they give you. Our windows might just be small. Anyway, give yourself three or four extra inches on each side just to be safe.
  4. Peel the backing paper off the tape. This is kind of fun.
  5. Adhere the film to the tape. You can actually stick it on fairly gently to start with, and then pull it off, stretch it and restick it until you have it as tight and smooth as possible. Then press it firmly onto the tape once you're happy with it.
  6. This is the fun part: use a blow dryer to heat the plastic so it shrinks like a giant shrinkydink and pulls all the remaining wrinkles out.
  7. Trim the excess film. Carefully. I was very conservative and left lots of extra because I didn't want to risk puncturing the film. Your mileage may vary.
  8. Stand back and admire your work. I'm really happy with how ours turned out; you can't see it at all from outside, and it's barely noticable from inside.

It took me about half an hour for each window, and I did it over a week or so. Kind of a big production and pain in the ass. I think it's helping with the cold thing though. Our big problem (apart from the aforementioned avalanche of cold) was condensation, and there's much less of it now, so clearly that cold is being stopped. I'm not sure if it's going to save us $70 in utility bills, though. But we'll probably do it again next year just for the increased comfort.

Anyway, so that's what I learned about insulating window film. Hopefully this is helpful to someone somewhere.

* Incidentally our blinds are awesome. We have honeycomb blinds from Hunter Douglas and they block a heck of a lot of cold. We saved a bunch on natural gas after we installed them, which is good because they were about a million dollars. I expect another brand of the same product would be equally effective, but the Hunter Douglas ones are very well made. I'm happy with them. (I wish we had got the top-down/bottom-up mechanism on all the blinds, though; the only window we didn't get it for was the living room, and sometimes I would like to open just the top of that, like in the morning in summer when I'm not dressed yet.)

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