Cold window in winter: faulty thermal pane or draft? How to tell the difference
You approach a window in the middle of winter and immediately feel the cold. Is the insulated glass unit broken? Is air leaking around the frame? Or is it simply the surface of the glass that's very cold? Before replacing anything, you need to identify the true source of the problem.
✓Distinguishing between a cold window and air infiltration
✓Knowing when to replace only the thermos
✓Montreal and Laval
experience
warranty on thermoses
residential service
Does your window become uncomfortably cold as soon as the temperature drops?
We can help you determine if the glazing is actually the problem.
It is often during the first very cold days that window problems become evident. A room that seemed comfortable in October can suddenly feel cold near a window when the outside temperature drops below zero.
The reflex is often to think, "There's air coming through." However, this isn't always the case. A very cold glass surface can itself create a feeling of discomfort, even when no air current is actually passing through the window.
Conversely, a worn weatherstrip, a poorly fitted opening, or a leak around the frame can cause a real water infiltration. And in some situations, it's rather the sealed glazing unit — the thermos — which must be evaluated.
Quick response
Feeling cold near a window does not automatically mean there is an air leak. If the glass becomes very cold, the air in the room near its surface can cool down and descend, creating the sensation of a draft. A true leak, however, is usually located in a specific area: around the sash, seals, frame, or hardware. Replacing the double-glazed unit can correct a problem with the glass itself, but it won't fix a leak originating from the frame.
Winter diagnosis
Three different problems can give the impression that your window is "letting in the cold"
To choose the right repair, you must first determine where the loss of comfort actually occurs.
The glass itself is very cold
You don't necessarily feel a specific draft, but you experience discomfort as soon as you approach the glass. The cold seems to come from the entire surface of the pane. In this case, the performance of the glazing and the condition of the double-glazed unit should be assessed.
A draft of air is noticeable around the opening
If cold air seems to enter in a very specific place — for example in a corner, along the frame or between the sash and its weatherstripping — the problem may be with the window seal rather than the thermos itself.
The thermos also shows condensation or marks between the panes.
When the glazing is cold and you also notice fog, droplets or an impossible-to-clean film between the two panels, the sealed unit clearly deserves to be checked.
A deceptive phenomenon
Why a cold window can give the impression of a draft
In winter, the temperature difference between the inside and outside of the house can be significant. The inner surface of the glazing then becomes colder than the surrounding walls.
The warm air in the room that comes into contact with this surface cools down. Because cooler air is denser, it can sink down the window. A person sitting near the glass can then feel this movement as a slight draft.
Key points to remember: A feeling of coldness spread across the entire window surface does not have the same cause as a localized draft around a seal. This is why a proper diagnosis must precede the replacement of a double-glazed window.
Do it yourself
A 5-minute diagnosis when the temperature drops
Take advantage of a cold day to compare your windows. The differences are often much easier to notice in the middle of winter.
Slowly run your hand near the edge
Without directly touching the glass, move your hand around the seals and corners. A clearly localized air leak may indicate a sealing problem.
Use a sheet of lightweight paper
Hold it near the window seals. If it moves repeatedly in a specific spot while the room is quiet, it may be worth having the window sash checked for leaks.
Compare with another window
Compare two similar windows located in the same house. If one pane feels noticeably colder or more uncomfortable than the other under comparable conditions, it warrants further inspection.
Look carefully between the glass panels
Condensation, a whitish film or traces trapped between the panes are additional signs that a thermos may have been unsealed.
When the glazing is the problem
When replacing the thermos might be the right solution
The double-glazed unit is the sealed unit of glass installed in your window frame. When this is the component that is actually defective and the rest of the window remains in good condition, it is often possible to replace only this part.
Replacing the thermos is worth considering if:
01The frame is solid and functional, but the glazing shows signs of failure.
02You see condensation or streaks between the panes of glass.
03A unit seems noticeably colder or less comfortable than other comparable windows.
04The glazing is cracked or damaged.
05You wish keep the existing window rather than unnecessarily replacing all its components.
Avoid a bad repair
What a new thermos won't fix
Replacing the glazing is very effective when the problem originates from the glazing itself. However, a double-glazed unit cannot address a problem located elsewhere within the window.
The principle is simple: Replace the double-glazed unit if the problem is the glass. If the draft is coming from the frame, weatherstripping, or installation, that cause should be addressed instead.
Cold season
Why do problems become much more visible in winter?
On a mild day, the difference between the indoor and outdoor temperatures is relatively small. Therefore, less efficient glazing or a small leak can go almost unnoticed.
When temperatures drop sharply, cold surfaces become easier to spot and leaks are generally more noticeable. It's also around this time that many homeowners first notice condensation, frost, or discomfort near certain windows.
Winter therefore becomes an excellent time to identify which windows are actually causing problems. It is then possible to target the necessary interventions rather than replacing all the windows simply because they are the same age.
How it works
If the thermos is the problem, does the entire window need to be replaced?
Not necessarily. When the frame, hardware, and other components are still in good condition, the sealed glazing can be replaced separately.
Identify the source of the cold
First, we determine whether the problem is related to the glazing or whether it originates from another element of the window.
Check the condition of the frame
If the frame is sound and functional, it can usually be retained during the glazing replacement.
Make the thermos to the correct dimensions
The new sealed unit must match the dimensions and characteristics of the existing window.
Install the new glazing
The old thermos is removed and the new one is installed in the existing frame when its condition allows it to be kept.
Avoid this winter
Three hasty conclusions when a window seems cold
"I feel cold, so there must be an air leak."
Not necessarily. A very cold glass surface can create a feeling of discomfort and air movement near the window without there being an opening to the outside.
"My window is cold, I have to replace everything."
The frame, hardware, and glazing are separate components. If only the double-glazed unit needs replacing, it may be unnecessary to replace the entire window.
"A new thermos will stop all drafts."
Only if the problem actually originates from the glazing. Leaks around the frame or weatherstripping must be diagnosed and repaired separately.
Montreal and Laval
Quebec's extreme cold quickly puts your windows to the test.
In Montreal and Laval, a window can experience significant temperature variations between the heated interior of the house and the outside air. It is often during these cold periods that the differences between two panes of glass become most apparent.
A window that seemed normal in the fall can suddenly become uncomfortable in December or January. This is also the time when a faulty thermos can become easier to spot.
Thermos Change Inc. specializes in replacing sealed glazing on existing windowswith over 20 years of experience in the field and a warranty of up to 10 years on thermoses.
FAQ
Frequently asked questions about cold windows in winter
Is it normal for a window to be cold to the touch in winter?
A window will normally be colder than an interior wall when it's very cold outside. What warrants more attention is a significant difference between comparable windows, marked discomfort, or the presence of other symptoms such as condensation between the panes.
How can I tell if I'm experiencing a cold window or a real air leak?
A real draft is often localized near a seal, corner, or frame. A feeling of cold caused by the glazing is usually more diffuse and seems to come from a larger area of the window surface.
Can a broken thermos make a window less comfortable in winter?
A thermos flask with a compromised seal no longer functions as intended. If you notice condensation or streaks between the panes, it is recommended to have the glazing unit checked.
Does changing the thermos eliminate drafts?
Not if air is getting in around the frame, a seal, or a weatherstrip. Replacing the double-glazed unit involves sealing the glass. That's why it's important to identify the exact source of the problem before starting any work.
Do I need to replace the entire window if the glazing is defective?
Not necessarily. If the frame, hardware, and other components are in good condition, it may be possible to replace only the insulated glass unit and keep the existing window.
What warranty is offered on thermoses?
Changement de Thermos Inc. offers a warranty of up to 10 years on its thermos units. The terms and conditions applicable to your project can be confirmed at the time of the quote.
Does your window get freezing cold as soon as winter arrives?
Before replacing the entire window, have it checked to see if the discomfort is actually coming from the double-glazed unit. If the frame is still in good condition, replacing the sealed glazing may be a much more targeted solution. Service available in Montreal and Laval.
Over 20 years of experience · Up to 10-year warranty on thermoses
Thermos Inc. Change
Replacement of sealed glazing on existing windows · Montreal and Laval
450-634-9525
