Preparing your windows for a Quebec winter: the complete guide to replacing double-glazed windows
Block heat loss before the cold weather arrives.
Autumn is the ideal time to prepare your home for winter. Up to 25% of a home's heat escapes through the windowsand a faulty thermos can single-handedly increase your heating bill by several hundred dollars.
In the Montreal and Laval region, winters put your windows to the test. The temperature difference between the heated interior at 21°C and the exterior, which drops below -25°C, creates enormous pressure on the sealed glazing of your windows.
Here's everything you need to know to prepare your windows before the first major cold snaps — and why replacing your thermos is the most cost-effective solution.
⚡ Quick response
Replacing a double-glazed window involves changing only the sealed pane of glass in your window.while preserving the existing frame. It's a quick intervention (often less than an hour per window), costs a fraction of the price of a complete window, and restores your home's energy efficiency before winter.
📊 The impact of windows on your heating
25%
Heat from a house escapes through the windows
50%
A significant portion of a Quebec household's energy budget goes towards heating.
-25°C
temperatures that your thermoses have to face each winter
Why do thermoses break down during the Quebec winter?
A thermos, also called sealed glazing Or sealed unitIt consists of two (or three) glass panels separated by a space filled with argon gas. This gas, denser than air, considerably slows down heat transfer.
In Quebec, this system is subjected to extreme stress. When it's -25°C outside and 21°C inside, the outer pane contracts while the inner pane expands. This movement is repeated season after season, eventually cracks the seal which keeps the argon gas in place.
Once the seal is compromised, the argon gas escapes and moisture seeps in. Your window then loses most of its insulating capacity — and becomes a veritable thermal sieve.
⚠️ Average lifespan of a thermos:
In the Quebec climate, sealed glazing has a typical lifespan of 15 to 20 years oldIf your windows are this old, it is very likely that several of the double-glazed units have already started to deteriorate, even without obvious visible signs.
How much does a faulty thermos cost on your heating bill?
Heating accounts for about half of a Quebec household's electricity consumption. When your windows let in heat, your heating system compensates by running longer and more frequently.
With defective thermos
Heat that escapes continuously
Electric baseboard heaters or heat pump running constantly. Feeling cold near the windows. Thermostat turned up to compensate.
Maximum winter bill
With new thermoses
Heat trapped inside
Heating system that reaches the set temperature and then shuts off. Uniform comfort throughout. Stable thermostat.
Savings from the first month
Over a full heating season (generally from October to April in Quebec), the difference can represent several hundred dollars depending on the size of your house and the number of windows affected.
Should the entire window be replaced, or just the insulated glass unit?
This is the most frequently asked question — and the answer often makes the difference between an expense of a few hundred dollars and a bill of several thousand.
✅ Replacing the thermos is sufficient if:
• The frame (PVC, aluminum or wood) is solid, straight and free from rot
• The opening mechanisms are functioning normally
• The problem is condensation, frost, or heat loss through the glazing.
• The frame's weatherstripping is in good condition
❌ Full window required if:
• The frame is rotten, deformed, or cracked
• Air is seeping in between the wall and the frame (structural problem)
• The mechanisms are broken and irreparable
• You want to change the size or style of the opening
In the vast majority of cases we encounter in Montreal and Laval, only the glazing is the problemThe frame still has 10 to 20 years of useful life ahead of it.
Inspect your windows before winter
01 Pass your hand near each window: can you feel the cold passing through?
02 Look for condensation or deposits between the two panes of glass.
03 Check if certain parts are colder than the others.
04 Test them draft excluder around the frame with a sheet of paper.
05 Compare your Hydro bill from last winter to that of two years ago.
06 Note the age of your windows: beyond 15 yearsAn inspection is necessary.
❓ Frequently Asked Questions
Can a thermos be replaced in winter?
Yes. Replacing a double-glazed window is done primarily from the inside and usually takes less than an hour per window. The opening is brief, and the impact on your home's temperature is minimal. That said, having the work done in the fall prevents you from experiencing heat loss throughout the cold season.
How long does a new thermos last?
A quality sealed unit installed in the Quebec climate typically lasts between 15 and 20 years. At Changement de Thermos Inc., our double-glazed units are covered by a warranty of up to 10 years.
What is argon gas and what is Low-E film?
Argon gas, an inert gas denser than air, is injected between the panes of glass to slow down heat transfer. Low-E (low-emissivity) film is a microscopic coating applied to the glass that reflects heat: in winter, it reflects heat from your heating system back inside; in summer, it blocks the sun's heat.
How much does it cost to replace a thermos unit compared to a complete window?
Replacing a double-glazed unit is a fraction of the cost of a new window, since you only pay for the sealed glazing and its installation—not for the frame, hardware, interior finishing, or additional labor. Because every situation is different, a free estimate will give you an accurate price.
Is replacing a thermos messy?
No. Unlike a complete window replacement—which requires removing the moldings, tearing out the frame, and redoing the insulation—replacing a double-glazed unit is limited to removing the glazing beads and the glass. No demolition, no construction dust, no paint or drywall touch-ups.
🍂
Autumn: the ideal time window
Acting before the onset of severe cold allows you to enjoy a comfortable home from the first frost, avoid a full season of heat loss, and benefit from shorter installation times than in the midst of a winter emergency.
✅ The benefits of a new thermos in winter
✓Reduced heating bill from the first month
✓End of cold zones near the windows
✓More than neither fog nor frost between the panes of glass
✓Heating system less in demand
✓Benefits also in summer against the heat
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Over 20 years of experience
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Warranty up to 10 years
⚡
Fast service in Montreal
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Free submission
Prepare your windows before the cold weather arrives.
Our experts inspect your thermoses and identify those that need to be replaced as a priority.
Fast service in Montreal and Laval.
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Thermos Inc. Change
Over 20 years of experience
Warranty up to 10 years
Fast service in Montreal and Laval
