Does window insulation film work?

Last Updated on February 13, 2021 by Dave Farquhar

I spent the afternoon putting plastic window insulation film on my windows. It was supposed to be a short project, and I do get better at it every year, but it still ended up taking about an hour per window. Was it worth it? Does window insulation film work?

Window insulation film is a cheap, effective way to save money and make your house more comfortable in the winter. It can cut your heating bills by 30 percent.

Where to buy window insulation film

The film comes in kits that you can buy at hardware or discount stores. The two brands I see most often are Frost King and 3M. I like 3M better–I think the tape holds better and comes off more easily at the end of the season, and I think the film is a little bit higher quality–but I buy the kits in the spring at a steep discount and store them until winter, so I don’t really get to pick and choose much. And the difference is slight.

I have 10 windows. Five of them have those awful aluminum frames from the 1960s, and many of them are single-pane. Insulating them makes them leak heat considerably less until I can replace them, and it’s cheap. Buying off season, it probably costs me $1 per window.

It’s not at all uncommon for someone to have $200 heating bills during the winter. Even if you pay full price, you’ll probably spend $20. Spending $20 to save $60-$90 is a good deal.

Making window insulation film stretch further

I have another trick to save money. In 2005, when I didn’t have a job and I didn’t have any money, I ran out of film and I still had windows to do. But I had saved my scraps. So I taped some scraps together with clear packing tape (a big roll costs $1 at Dollar Tree). The resulting piece fit one of the remaining windows. It worked fine. It didn’t look good. But at the time I was making $400 a week doing odd jobs so I didn’t care about appearances.

This year I wasn’t going to do that. I had so much film, I was going to have some left over to do one of the smaller windows next year. But the piece for my sliding glass door was considerably smaller than the box said. And of course by the time I realized it, I’d already cut the piece and ended up with something that covered approximately half the door. Worse yet, it was 8 pm and all the stores were closed. So going and buying a new kit, at full price, wasn’t an option. My Scottish blood probably would have staged a revolt at that, but the option wasn’t on the table.

I can justify it another way too, though. Oil is at $100 per barrel now. Do I need to consume more oil just to avoid having seams in my sliding glass door? I think I’ll save some money and conserve a small amount of oil and live with the seams.

One way I found to reduce the seams is to mount the scraps on the window as tightly as possible, then put packing tape over the joint. I used to lay the pieces on the floor and tape them together before mounting. But I think taping the mounted pieces ends up looking better, and the process goes faster. Surprisingly, when I shrink the film with the hair dryer, it doesn’t seem to have much negative effect on the cheap dollar-store packing tape I use.

Cheaper substitutes

Some people skip the kits altogether and just buy the tape (3M’s tape is available separately), and either buy a roll of shrinkwrap film from a packing supply store or a big roll of food-grade film from Costco and use that. That may be an even cheaper option than buying the kits off-season, and it’s certainly more convenient. I don’t know what those rolls cost, but I would think one of those would last at least three or four years, if not 10. Plus there would be very little waste.

While it’s difficult for me to calculate exactly how much using window insulation film has saved me, I know it’s saved me at least $40. So I know window insulation film does work. Here are some more tricks for cutting your energy usage.