Stop Heat Loss with Window Insulation

Windows can account for at least 25% of heating loss, perhaps as much as 37%. If you are looking for something quick and easy you can do to minimize your heating bill, this should be on your list.

There are an increasing number of options these days but here we will focus on the least expensive. The best is probably buying new energy efficient windows with special coatings added during the manufacturing process but that is an investment and for those Americans battling the mortgage disaster, giving even more money to the house is not on. Next option please….

Insulating films that require a blowdryer to install

It comes in boxes that cover a couple of windows and it also comes in roles. It is sometimes called ‘shrink film’ or ‘window insulating kit’. It adheres to the window frame rather than the window so that there is an airspace between the film and the window. This airspace is your friend: it acts as insulation.

The potential sloppiness of this Saran Wrap-like film is limited by using a blowdryer to slightly heat the film. The heat causes the film to contract and voilà – the bagginess disappears. Distortion is minimal and heat savings are significant. The cost of the film is very low. At Home Depot in Canada, it is about $20 for 5.5 ft x 25 ft. About the same with Revy/Rona. If you don’t have a blow dryer, you can use a heatgun instead according to this forum.

A few tips (feel free to add your comments below!): Do not trim the edges for a few days! Sometimes the tape will not stick to irregular edges and will peel away. This means there will be an unfixable hole along the edge and you will have to buy another sheet and redo it. Also, doing it in the evening makes it easier to see the irregularities. All in all, strangely satisfying to install! I think there are probably people out there shrink-filming triple-glazed windows due to the sheer pleasure of being able to make something in life visibly perfect in 20 minutes.

Insulating films that use a squeegee

Many of the companies that sell the film have an installer service as well but here is a company in Toronto that also ships the same film so that you can do-it-yourself without paying for an installer. They ship to the US and internationally. It is also available at Home Depot with a few tips for Canadians in the reviews.

This film goes directly onto the window pane and can be removed in the future (though some say this is not a simple task). According to the American hardware chain Lowes, “insulating films retain as much as 55% of a home’s heat in winter”. There is a convenient video at the bottom of the Lowe’s page that will give you an idea of how this works.

Here is a list of important tips for applying this kind of film. And reviews and tips from Under some circumstances, the film can cause the glass to break. Good to know. Here is another helpful American site. They ship to Canada.

Figures on exactly how much heat will be retained and how much of a savings that translates to are confusing at best. Figures on how much summer heat is repelled are not comparable to the amount of interior winter heating is retained.

Wikipedia’s entry on this kind of insulating film is here. Note the difference when applying the film to keep the windows cool from the summer heat vs. applying it to keep the heat inside for winter energy savings. Very important.

Vinyl curtain with magnetic seal

If you have a cat that yearns for window ledges, this one’s for you. Apparently, you can secure the film to the surrounding wall with magnets and magnetic paint. The film itself is vinyl – much heavier than the shrink film. You can buy vinyl by the inch at a fabric store. (It comes in rolls and you ask the clerk to cut the size you want). You might also experiment with clear shower curtains. Remember that vinyl smells initially.

Insulating films that use ‘static cling’

I am not sure how different this is from wetting your windows, sticking a piece of vinyl on the window, and using a squeegee to push out the bubbles. I have a feeling the air pocket created by the alternative ‘vinyl curtain’ option is more insulating than this approach. Nonetheless, here is the link to an American company that sells this ‘static cling’ film. The site says it blocks up to 38% of window heat loss. They ship internationally but only by phone orders. It is also available at Home Depot in Canada.


Ahhhh – the alluring opaque light of a traditional Japanese shoji blind in… a playful petrochemical packing product! More interesting than you might think. Here is a photo from the website of one of my favourite eco-housing innovators in Australia along with a link to more details and additional photos. Note that he puts the bubbles facing the window for maximum insulation. Get distracted by his chest fridge alternative….

The website Built It Solar indicates that bubblewrap is cheap, quick to install (15 seconds!), effective, and can be easily removed if guests visit. It acts as a second pane of glass and cuts heat loss through windows by half. Not too shabby! Some other very cool DIY projects for environmental experimenters are on Built It Solar.

Note to Canadians: the maximum width of the bubblewrap you can buy at Staples/Bureau en gros is only 24 inches. Home Depot and Rona/Revy do not carry it. (They carry Reflectrix – which is bubblewrap for your radiators – a future post!) If your windows are larger (or you have some interesting design plans), you will have to special order it from either, based in Toronto or from, which is based in Montreal. Both ship countrywide. Most other places seem to sell it in 250 foot rolls. I think bubblewrap would work better as an ‘accent piece’…. The maximum available width is 48″. It would be nice if it came in 36″ but I cannot find it anywhere. There is coloured bubblewrap – intriguing – but the max width is 12″ and the colours are garish party colours.

The Toyota Prius of Blinds?: The Honeycomb or Cellular blind

Another product that uses air pockets as insulation but unlike shrink film, it can be rolled up. Obviously these will look a bit more polished than the shrink film but they will also cost more. They come in various formations with different R-Values. Before you outfit your home or apartment with these, remember that windows are responsible for only some of a building’s heat loss. An overview of the technology and the cost is here but they ship only in the USA. See for tips on ordering and measuring blinds (they also ship to Canada).

Special Insulating Curtains

If you don’t really like blinds or think they make the room look too boxy, you can buy insulated curtains here (shipping info is here) or make them yourself, possibly out of Reflectrix. How tight to the window does it have to be? Some data here.


3 responses to “Stop Heat Loss with Window Insulation

  1. There are some very detailed instructions for installing the window shrink film at

  2. I would definitely agree that vinyl replacement windows with Low E Argon filled insulated glass that qualify for the Federal Tax Energy Credit is the way to go. Not only do you qualify for the Energy Credit, but the glass also has a lifetime guarantee against dust or fogginess between the panes. Shrink film is a temporary solution, but not permanent.

  3. Thanks for the link! We actually do ship internationally and are located quite close to the Canadian border. We have the best warranty in the industry!

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