When a window fogs up or breaks, you're often told everything must be replaced. Yet in the vast majority of cases, only the thermos — the sealed unit — is at fault. The right answer depends on one thing: the condition of the frame.
Evaluating the condition of the frame
The frame is the determining factor. If it's sound — no rot, no warping, working hardware — then the window itself is good, and only the glass needs replacing. If it's damaged, replacing it with a new thermos would be a waste.
Cases where the thermos is enough
- The fog is between the panes (failed seal)
- A pane is cracked or broken, but the frame is sound
- The window still opens and closes properly
- The frame shows no rot or warping
In all these cases, replacing only the sealed unit is the most economical and equally durable solution. See our process on the thermos replacement page. Thermos replacement.
Cases where you should replace
- The frame is rotten, warped or damaged
- It's outdated single glazing that deserves a real upgrade
- The opening mechanism is broken
- There are water or air leaks around the frame
- You're renovating or changing the style
In these situations, we tell you honestly and connect you with trusted RBQ partner installers, at no cost and with no hidden commission.
The cost comparison
| Criteria | Thermos | Full window |
|---|---|---|
| Estimated cost | 150 – 450 $ | 700 – 1 200 $+ |
| Timeline | 24–72 h | Several weeks |
| Work | Frame kept | Full removal |
The window-salesperson trap
Some salespeople have an interest in selling you a new window, even when a simple thermos replacement would do. Their argument is often the same: "your window is too old", "might as well replace everything". It's sometimes true, but not always.
The healthy reflex: ask for an independent diagnosis of the frame's condition. If the frame is good, replacing the thermos is more than enough and saves you hundreds of dollars.
Our honest approach
Our promise is simple: if a thermos is enough, we say so. If the whole window needs replacing, we say that too and point you to a trusted RBQ installer, free of charge. Our reputation is worth more than a forced sale.
Want to settle the question? See our dedicated decision page, or request a free quote. Repair or replace the window?.
