Can You Replace Just the Glass in Double Glazing?
7 min read
If your window has gone cloudy, has condensation trapped between the panes or has a crack across it, the good news is that the frame is almost never the problem. In most cases only the sealed glass unit needs replacing — a quicker, tidier and far cheaper job than a new window.
How a double glazed unit actually works
A double glazed window is really two parts: the frame (uPVC, aluminium or timber) and the sealed unit — two panes of glass held apart by a spacer bar and sealed around the edge.
The gap between the panes is filled with dry air or an insulating gas such as argon. Inside the spacer bar is a desiccant, a moisture-absorbing material that keeps that gap bone dry.
As long as the edge seal holds, the unit stays clear and insulates well. When the seal fails, damp air gets in, the desiccant becomes saturated and you start to see misting between the panes.
Signs the glass unit has failed
These are the usual symptoms we're called out for:
- Condensation or fogging between the two panes that you can't wipe away
- A milky or cloudy film that comes and goes with the weather
- Water droplets or streaks running inside the unit
- A crack or chip in either pane
- The room near the window feeling noticeably colder than it used to
Why you usually don't need a new window
Frames are built to last decades. A sealed unit has a shorter life because its edge seal is constantly expanding and contracting with the sun and cold. That means the glass often fails long before the frame does.
Swapping the sealed unit keeps your existing frame, colour, handles and finish exactly as they are. There's no plastering, no making good, and no matching new frames to the rest of the house.
The exception is a frame that is genuinely rotten, warped or cracked — in that case we'll tell you honestly before any work is quoted.
What happens on the day
Replacing a sealed unit is a clean, quick job:
- We measure the existing unit precisely and note the glass type (clear, obscure, toughened, Georgian bar, etc.)
- A new unit is made to size
- On fitting day, the glazing beads are unclipped, the old unit removed and the new one packed and set level
- Beads go back in, the window is checked for smooth opening and the old glass is taken away
Can't I just get the moisture removed?
Some firms offer to drill and 'de-mist' a unit. It can clear the view for a while, but it doesn't restore the failed edge seal or the insulating gas, so misting often returns. A replacement unit restores both the clear view and the insulation.
Need it fixed?
We cover Northampton, Northamptonshire and Milton Keynes. Free, no-obligation quotes.
Common questions
- Can misted double glazing be repaired?
- Yes. The usual fix is replacing the sealed glass unit only, keeping your existing frame.
- Do I need planning permission to replace the glass?
- No. Replacing a sealed unit like-for-like in an existing frame doesn't need planning permission.
- Will the new glass match my other windows?
- We match the glass type, thickness and any obscure pattern or bars as closely as possible to your existing units.