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Check Your Window Sash Seals Before Winter

17 October 2016

Here are a few tips to help you check your window seals before winter.

Perhaps you noticed that your home was a bit draftier than normal this past winter. Maybe your heating bill was just a little higher than average, even though you’ve been keeping your thermostat at the same temperature. You might just have a broken window sash seal. Windows carry the burden of keeping homes toasty and warm throughout the winter–and that is a big burden! If the seal on your window sash has broken, it won’t perform as well as it could, and you’ll be living with (and paying for) air leaks during those cold months. How do you know which window it is that has a broken seal? Here are a few tips to help you check your window seals, so you know exactly which window needs to be replaced or repaired before winter.

Windows carry the burden of keeping homes toasty and warm throughout the winter. If the seal on your window sash has broken, it won’t perform as well as it could.

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First, what do you mean by window sash seal?

The window sash is the part of the window that actually slides open. There are really two different seals associated with the sash: the seal between double paned windows that keeps your windows insulated, and the weatherstripping on the side jambs and the bottom of the sash. Both seals affect how well your sash keeps your home warm during winter months.

Double Paned Seal

Most windows these days are double paned, meaning that they have two panes of glass on each sash. In between the panes of glass there is an insulating gas, usually Krypton or Argon, that helps to create a buffer between the cold air on the outside pane of glass, and the warm air on the inside pane of glass. If the seal has broken and the insulating air has escaped, your window is as only useful as a single paned window and storm window combination. The bad news: there is no way to repair this kind of seal. Once the seal has blown, the only thing you can do is replace the window. Consider your heating cost against the cost of a new window.


Weatherstripping typically comes on all new windows these days. However, it gets worn out and needs to be replaced. What weatherstripping does is create a tighter seal between the moving parts of your window. It’s a flexible material that adheres to the side jambs and bottom of the sash. It’s an added barrier that keeps out those drafts. The good news: weatherstripping is easy and inexpensive to replace if it’s worn out.

Ways to Check your Window Sash Seals

Most of the time your windows will just tell you that something is wrong. There are a couple other things you can do if your windows look fine, but you suspect that they’re less effective than they used to be.

  1. Observe

Once the weather is getting cooler, you might notice condensation or moisture between your double paned windows. If you see condensation between panes, this is a sure sign that the seal has blown. This means that the added insulating gas between pane has either escaped or settled at the bottom.

Weatherstripping can come loose after a handful of years. This can happen during any season, and you would be able to see it coming off the sides or the sash.

  1. Ice cube Trick

If you suspect that the seal between your window panes as blown, but you haven’t seen any condensation or moisture, you can try the ice cube trick. Basically all you need to do is rub an ice cube on your window for a few minutes. If the inside of the window pane fogs up–meaning you can’t wipe off the condensation–then the seal has blown, and your only option is replacement. Here’s a video showing how to do this.

  1. Candle Trick

This trick will help you check the performance of your weatherstripping if you can’t tell if it’s loose. It’s pretty simple and commonsense. On a windy day, close your window and lock it. Locking your window actually helps it seal better. Hold a candle up to the sides and bottom of your window. If the candle flickers, it’s time to replace your weatherstripping.

Well performing windows do so much for your home, and so do your gutters! Once you’re done checking your windows, check out LeafGuard’s maintenance-free gutters.

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