Window glass replacement is the process of swapping out only the insulated glass unit (the “sealed unit” or “thermopane”) inside your existing window frame, while full window replacement removes and replaces the entire window — frame, sash, hardware, and glass. The distinction matters enormously for your budget: in most cases where the frame is still sound, replacing just the glass solves the problem for a fraction of the cost of a new window.
At Centennial Glass, we have been making this exact call for Ottawa homeowners since 1967. Because we offer both services — and fabricate sealed units in-house — we can recommend whichever option genuinely fits your situation, not the one that pads the invoice.
What Is a Sealed Unit, and Why Does It Fail?
A sealed unit is the factory-assembled package of two or three panes of glass separated by a spacer and sealed around the edges, often with an insulating gas between the panes. Almost every modern window contains one. You can read a plain-language explanation on our page about insulated glass units.
Over time, the edge seal can fail. When it does, moist air gets between the panes and you see fog, condensation, or mineral staining that you cannot wipe away from either side. The window also loses some of its insulating value. This is the single most common “my window is done” complaint we hear — and crucially, it is a glass problem, not a window problem. Our FAQ on foggy windows and sealed unit replacement covers the details.
When Glass-Only Replacement Is the Right Call
Choose sealed unit or thermopane replacement when:
- The glass is foggy or has condensation between the panes. A new sealed unit restores clarity and insulating performance. See our guide to getting rid of foggy windows for what is actually happening inside the glass.
- The glass is cracked or broken but the frame is fine. There is no reason to replace a healthy frame because a pane broke.
- The window operates normally. If it opens, closes, and locks smoothly, the frame and hardware are doing their job.
- The frame shows no rot, warping, or structural damage. Vinyl, aluminum, and well-maintained wood frames often outlast their glass by many years.
Because Centennial fabricates glass in-house in Ottawa, sealed units are made to your window’s exact measurements, and many repairs can be completed quickly — same-day service is available for many repair jobs.
When Full Window Replacement Makes More Sense
Choose a complete window installation when:
- The frame is rotted, swollen, or structurally compromised. New glass in a failing frame is money spent twice.
- Air leaks around the frame perimeter, not through the glass. If drafts come from where the window meets the wall, the installation itself has failed.
- You are renovating and want a different style, size, or configuration. Glass replacement keeps the window you have; full replacement lets you change it.
- The window is very old single-pane construction. There is no sealed unit to swap; upgrading to modern insulated glass means a new window.
- Multiple components are failing at once. When glass, hardware, weatherstripping, and frame are all tired, replacement is usually the better long-term spend.
Our FAQ on window replacement and thermopane or seal units explains how we assess which path fits.
The Repair-First Difference
Plenty of window companies only sell full replacements, so every problem they see looks like a replacement job. Centennial Glass is split roughly 50/50 between residential and commercial work, and repair has been core to our business for over 55 years — which means recommending a sealed-unit swap instead of a new window is a normal day for us, not a lost sale. Customers notice the difference:
“I had a glass panel replaced of a window that has 2 panels as it had lost its seal. The service was very efficient and reliable The installer was extremely courteous and friendly. I recommend this company.” — Irene Savage, 5★
“Excellent service for replacing sealed glass units. Jordan and Tony did the installation quickly and cleanly, very professional.” — David myer, 5★
FAQ: Glass Replacement vs Window Replacement
How do I know if only the glass needs replacing?
If the fog, condensation, or crack is in the glass itself but the window still opens, closes, and seals properly — and the frame is solid — a glass-only sealed unit replacement is usually all you need. A professional assessment confirms it in minutes.
Is replacing the glass as good as replacing the window?
For insulating performance, yes: a new sealed unit can be built with modern Low-E glass and gas fill, restoring or even improving the original thermal performance. What it cannot fix is a failing frame or poor original installation.
How long does sealed unit replacement take?
Once your replacement unit is fabricated to measure, the swap itself is typically quick — often under an hour per window. Centennial’s in-house fabrication shortens the wait between measurement and installation.
Can old wooden windows get new sealed units?
Often, yes — if the wood frame and sash are still sound, a new sealed unit can be fitted. If the wood itself has deteriorated, full replacement is the more durable answer.
Not Sure Which You Need? Ask Us — We Do Both
The fastest way to settle the repair-versus-replace question is to have someone look at your actual windows. Centennial Glass has been doing exactly that across the Ottawa region for 55+ years. Call us at 613-738-9500 or contact Centennial Glass and we will tell you honestly which option you need.