Published · Vitrerie Vaudreuil
Fog trapped between the two panes almost always signals that a thermos (sealed unit) replacement is needed in Longueuil or elsewhere in Vaudreuil-Soulanges. The seal on the sealed unit has failed, letting moisture seep in between the panes of glass. The good news: usually only the sealed unit needs replacing, not the entire window.
Why a thermos fogs up
The thermos, also called a sealed unit, is made up of two or three panes of glass separated by an airtight space filled with insulating gas. This system works well as long as the perimeter seal stays intact. Once that seal breaks, outside air and moisture start getting into the cavity. The fog that shows up between the panes at that point isn't ordinary condensation on the inside surface of a window: it stays trapped, doesn't clear up with a simple wipe, and comes right back even after you clean the glass.
It's important to tell this apart from condensation that forms inside the house on the glass, which is often linked to indoor humidity levels or poor air circulation near the window. That kind of condensation can be fixed without replacing anything. Fog stuck between the panes, on the other hand, points to a broken seal and calls for a thermos replacement.
Replace the sealed unit or the whole window?
In most residential cases, the frame and the window's mechanism remain in good working order even when the thermos has failed. That means it's often possible to replace only the sealed unit, avoiding a full window or door replacement. This approach applies to windows as well as glass doors and certain glazed sections of patio doors.
A full replacement only makes sense if the frame is damaged, the opening mechanism is broken, or you'd like to take advantage of the change to improve the overall insulation of the opening. An on-site assessment helps determine the most sensible option for your situation.
Signs that a replacement is warranted
- Persistent fog or haze between the panes, even in dry weather
- Whitish deposits or mineral traces visible inside the sealed space
- A cold draft near the glass despite the window being closed
- A noticeable temperature difference to the touch between the centre and edges of the pane
- Older glazing showing signs of general wear
If even one of these signs shows up on a window that's otherwise in good shape, it's usually a textbook case for a sealed unit replacement rather than a bigger issue.
What affects the price of a replacement
No fixed price can be quoted without seeing the window in question, but a number of concrete factors influence the cost of a project:
- The surface area and shape of the glazing to be replaced
- The type of glass chosen (clear, frosted, low-e, patterned)
- The condition of the surrounding frame and the prep work needed before installation
- How accessible the window or door in question is
- The number of units to be replaced in a single project
Since final dimensions are always confirmed on site, the only reliable way to get an accurate figure is to have your situation assessed directly. You can request a free quote by describing your project.
Service in Vaudreuil-Soulanges
Vitrerie Vaudreuil offers sealed unit replacement as well as installation and repair of residential doors and windows across the Vaudreuil-Soulanges area. The process starts with a quote request through the project form, followed by a visit to confirm the exact dimensions before anything is ordered. This step matters because every opening has its own quirks, even between two homes built around the same time.
To see which municipalities are covered by this service, check out the service area page. Other topics related to residential window and glass upkeep are also covered on the blog.
Upkeep after the replacement
Once the sealed unit has been replaced, there's no special upkeep required beyond regular glass cleaning. Good air circulation near the windows and reasonable indoor humidity levels help limit surface condensation, which remains a separate phenomenon from fog trapped inside a failed thermos. If fog reappears between the panes shortly after a replacement, it's a situation worth having checked out quickly.
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Frequently asked questions
What's the price to replace thermal (thermos) window panes?
There's no fixed price since the cost depends on the surface area, the type of glass, and the condition of the frame. Dimensions are confirmed on site before providing an exact figure. The best way to find out the cost for your situation is to request a free quote.
How much does it cost to replace a patio door thermos?
The cost varies depending on the size of the door's glazing, the type of glass desired, and how accessible the installation is. As with windows, an on-site assessment is needed to give a reliable figure. Requesting a quote gives you a clear picture of your project.
What's the lifespan of a thermos (sealed unit)?
The lifespan of a sealed unit depends on the quality of the original product, exposure to sun and weather, and the quality of the initial installation. Some sealed units last for many years without issue, while others start showing signs of seal failure sooner. A visual inspection remains the most reliable way to check the current condition of your glazing.
Can only the sealed unit be replaced without changing the entire window?
Yes, in most residential cases in Vaudreuil-Soulanges, the frame remains functional and only the sealed unit needs to be replaced. A full window replacement is only necessary if the frame or opening mechanism is also damaged. An on-site visit confirms the appropriate option.
How can you tell if fog is caused by a faulty sealed unit or an indoor humidity problem?
Fog trapped between the two panes, which doesn't clear up with cleaning, indicates a broken seal on the sealed unit. Condensation that forms on the inside surface of the glass, on the other hand, is usually linked to the home's indoor humidity levels. These two situations call for different solutions.