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Drafty windows are the worst. There are few things that can ruin a cozy movie night or enjoyable game like sitting in front of a window that leaks like a sieve. You can almost see the heat escaping while picturing your utility meters spinning like a slot machine. That cold air is just uncomfortable—for you and your bank account.
That’s why we tested several of the best window insulation kits. We wanted to offer folks with older, possibly single-pane windows a way to keep their homes warmer and more efficient without an expensive window replacement. After days of testing, I determined that the 3M Window Insulator Kit was the product that came out on top. Keep reading to find out why it was our best overall window insulation kit and to see if it’s a good fit for you and your home.
3M Window Insulator Kit: At a Glance
Rating: 9.1/10
SPECS
- Length: 17.5 feet
- Thickness: .75 mils
- Window coverage: Five 3-foot by 5-foot windows
PROS
- Plastic can be repositioned a few times before pressing down for a permanent bond
- A single kit can cover multiple average-size windows
- The wrinkles were easy to heat out for a very clear installation
CONS
- Installation can lead to waste if you’re not careful
Get the 3M Window Insulator Kit at:
What is the 3M Window Insulator Kit?
The 3M Window Insulator Kit is a plastic-based window film and tape kit that allows users to improve their homes’ efficiency. Energy.gov states that up to 30 percent of a home’s heat loss or gain is through its windows, and winter exploits this fact. Heated air is drawn toward cooler air, and many windows with poor insulation or older designs allow air to easily escape. The 3M Window Insulator Kit aims to combat this.
This kit from 3M includes a film that is .75 mils thick, which was about the average for the products in our test. It also contains strong double-sided tape. The installer applies the tape around the window and then installs the film over top. This creates an air barrier that helps prevent heat energy from bridging across the glass while preventing cold air from entering the home. While it’s hard to tell just how efficient window films are without a test laboratory, the principles are sound.
This kit contains enough film and tape to cover five 3-foot by 5-foot windows. It comes in one sheet of film, so it can be cut to fit larger, wider windows as well.
Cut, Tape, and Use a Hair Dryer for Easy Installation
All of the kits in our test followed the same concept of applying tape and then applying the film. However, some were easier to install than others. Some films came in rolls, which allowed the user to roll the film across the window and then unfold it, but 3M’s came in a folded sheet, which was my preferred method of installation.
Installation involved:
- Apply the tape to the window. If your window doesn’t have a stool or sill that sticks out, you can run the tape all along the window casing. However, if you have large sills, you’ll have to run the tape across the sill and get somewhat creative.
- Cut the film to the correct width. It should be a few inches wider than the taped area. You can measure and cut it or place it against the window for a quick guide.
- Remove the backing from the double-sided tape.
- Unfold the film and apply it to the tape. Don’t apply pressure until the film is nicely laid out on the windows. Wrinkles in the middle of the film are OK, but wrinkles in the tape are not good.
- Firmly press the film into the tape with a dull object that won’t tear the film.
- Heat the film with a hair dryer (a heat gun is likely too hot) to shrink the film and remove the wrinkles.
The 3M kit was very easy to install following this procedure. However, there’s one challenge that installers should recognize before cutting. Sometimes, finding the edge of this film is difficult, and if you’re not sure that you have the true edge, you could accidentally apply a folded piece of film to the window. If it won’t unfold enough to cover the window, you’re going to have to start over, wasting much of the product.
Simple Yet Superior Design
The 3M Window Insulator Kit comes in one folded sheet that is then rolled up into a flattened roll. I preferred this option because it was easy to lay out and cut to the length prior to installing. The other options include a roll of window film that is applied to the window, rolled across the window, and then cut. I found that this was more difficult to coordinate. This is an area where the 3M film really leaped ahead.
Also, while it’s certainly not the thickest film in the group (and thicker generally means tougher), there is a major benefit to it. The 3M Window Insulator Kit film is very easy to remove wrinkles from. The film shrinks easily within a few minutes, leaving behind an almost perfectly clear film. For anyone considering one of these kits but holding off for fear it’ll look tacky, the 3M kit is by far the best at being the least noticeable.
Full Transparency of 3M Window Insulator Kit Performance
It’s hard to quantify performance in an actual home. There are a lot of factors to consider, such as each window’s installation, insulation, position in the house, and more. Also, temperatures fluctuate throughout the day, and wind is also a factor. In short, it’s almost impossible to put a definitive answer on how well any one kit from the original test performed. I would’ve needed a laboratory full of scientific equipment (and a few more years of schooling) to make that determination.
However, the 3M kit was effective at reducing the cold air felt near the window. It also stayed secure and didn’t peel or pop loose during testing. When it came time to remove the film (an act I was concerned would peel paint from my trim), it removed cleanly and quickly.
In full transparency (pun intended), it’s important to note that all of the other kits were equally as capable of keeping cold air at bay and removed easily as well.
Is the 3M Window Insulator Kit worth the money?
Absolutely. For around $22, shoppers will get enough window film to cover five windows with this one kit. It comes with several rolls of tape and the film required. While I’m not sure if you’ll save $4.20 (the cost of film and tape for each window) over the course of the winter in energy savings, the kit will make it much more comfortable to sit in front of the window without shivering.
There are less expensive kits on the market, some of which we tested. However, few offer as much coverage with as few wrinkles and as smooth an installation process as the 3M kit. It also provided the clearest film once installed, while many others showed permanent creases from folds or even marks from the machines used to create the film in the factory. For these reasons, there is certainly value to be had in this kit.
Is the 3M Window Insulator Kit right for you?
The short answer is, it depends. There are folks who should not buy this insulation kit, or any kit for that matter. First, if you live in an area that doesn’t get extremely cold during the winter, window insulation kits aren’t worth it. Second, if you’re someone who likes to open your windows on the warmer days during the winter, a film kit will not help you. In both of these cases, a heavy curtain might be a better option. The best thermal curtains do a good job of preventing heat transfer when they’re closed, but they allow users to open their windows if they’d like some fresh air on warmer days.
If you have a very large window or patio door to cover, this kit won’t work for you. Instead, 3M’s XL window kit comes with enough film to cover a full-size bay window or patio door or two (the film is a total of 19.7 feet long).
However, if your windows are leaky and drafty, and you don’t want to go through the expense and hassle of replacing them this year, get this kit. You can install it quickly and easily, and it will make a tremendous difference in the comfort of your home, specifically in front of those windows. This one kit contains enough film to do a large room’s worth of windows or several small windows in bedrooms or bathrooms. Rather than dealing with the cold air pouring through and knowing your warm air is escaping, you can put a cork on that airflow with this kit from 3M.
Where to Buy the 3M Window Insulator Kit
Get the 3M Window Insulator Kit at:
Meet the Tester
Tom Scalisi is a full-time DIY and construction writer for many of the largest websites in the industry, including BobVila.com, This Old House, Family Handyman, and Forbes. He has installed and replaced countless windows during his time as a contractor, and he knows what it takes to keep cold air out and warm air in during his native Northeast’s winters.