Winter window insulation tips

Last updated on March 10th, 2024 at 03:33 pm

The easy answer to a drafty or old window that no longer insulates well is to “cover it in plastic.” And that still is probably the best possible answer for most situations.

Most situations?

Yup. I said most situations for a reason. Here’s why. You need to know how the window is losing your home’s energy to effectively make the right repair choice.

For example, putting plastic over a window when its the outer frame that loses energy will do next to nothing except obscure your view of the outdoors.

Okay, so how can you figure out exactly what’s wrong with your window?

  1. The tissue or candle test. If you suspect an air leak, on a breezy day take a 1 ply tissue and slowly (and lightly) drag it along the window pane and sill, as well as the framing around the window. The 1 ply tissue should remain relatively calm and not wave too much. If it does, there is an air leak there, and energy is being lost.

    You can do a similar test with a lit candle. The flame is very sensitive, so it should remain relatively still, if it bows, there is an air leak. If you don’t feel comfortable with a lit candle, light it, then extinguish. The rising smoke plume is just as sensitive (if not more so) to air flow.

  2. Take temperature readings. Using a probe or Infrared thermometer, take temperature readings of the window. If insulated well, the window surface and surroundings should be roughly equal. If not, the areas that show a temperature differential are losing energy, and thus costing you money.
  3. Inspect the area/caulking around the window panes. If loose, cracked, or peeling, it could be part of the problem. Of course, cracked glass is always a problem, both for safety reasons and energy reasons.
  4. Check the seal between the window (where it opens) and where it comes in contact with the frame.


Now that we covered some common energy points of windows, lets cover some effective ways of fixing the problems.

If you find that the window panes or inner part of the window frame is solid and not the problem, you’ll probably want to simply caulk or weatherstrip the problem areas. Cracks, splits, and other issues with the frame and molding (woodwork) around the window can’t really be solved by putting plastic over the the window.

If you determine that a portion of the inner window, such as the pane, glass, interior woodwork, or framing is faulty, placing plastic over the window will be more effective. You should also try and repair the problem itself with caulk or another type of weatherstripping.

The most common problem with windows, especially in older homes, is the glass. It is thin and not a very effective insulator. Unfortunately there are only a few things you can do to improve the insulative qualities of the older glass. One thing is special insulative film that can be cut and placed on the window. Another is plastic. If your glass panes are faulty, all the caulking in the world will not improve your insulation on the window.

Caulk is really one of your best friends when it comes to window repair. It insulates well and is effective in reducing drafts. It can seal problems between glass panes and the frame, and is flexible so it will fit around corners nicely. It can be smoothed out to give a professional appearance and is available in many different colors, most commonly in white.

Putty is also effective in filling gaps in wood toned frames. It is malleable, flexible when it goes on and also stops drafts.

If you find you have a drafty window as a whole, or simply can not identify the problem give it the “blanket” treatment. Caulk around the frame to seal gaps, inspect the panes, use plastic and increase the seal be placing foam tape or vinyl or rubber gaskets where the window meets the frame (aka the opening point.) Lock the window as this forms a tighter seal. Then, make sure you have heavy curtains over the window with numerous folds, as these reduce drafts leaking into the home. If you don’t have these curtains, a heavy blanket hung in place of it works relatively well. Try to stay away from placing newspapers over the window – they are thin, don’t insulate well, and don’t look very nice.

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