A window that looks tired might need one of three things: a new sealed unit, a repair to the frame, or a whole new window. They are different jobs at very different prices, and the faults overlap enough to confuse people. This guide helps you work out which one you have.
Start with the question that decides it
Is the frame in good shape? If it opens and closes smoothly, shuts tight, has no splits at the corners and no soft timber, then glass is likely the only problem, and the answer is new sealed units. If the frame is the problem, new glass will not fix it. A fresh unit in a warped frame lets in the same draught.
Which fault points to which fix
| Fault | Probably glass or frame? | Fix |
|---|---|---|
| Moisture or film between the panes | Glass | Replace the sealed unit |
| Condensation on the inside of the room face | Neither, usually ventilation | See our condensation guide |
| Draught round a closed opener | Frame, seals or hinges | Adjust, re-seal, or replace the window |
| Draught through the frame itself | Frame | Replace the window |
| Cracked pane | Glass | Replace the unit or the pane |
| Black spots or a soft sill | Frame | Repair or replace, depending on extent |
| Misting on several windows from the same era | Glass, but check the frames too | Compare the cost of units against new windows |
Misted glass
A sealed unit is two panes with a spacer round the edge and a gas or air space between. When the seal fails, moist air gets in and condenses on the inside faces of the glass. You cannot wipe it off, and it does not go away. It usually shows first on cold mornings and clears slightly in dry weather.
Replacing the unit costs far less than a window, in the range of about £150–£600 for a few units according to the double glazing replacement pricing on this site. It also resets the insulation and often improves the look of the window. Many units have a date stamped on the spacer bar, which can tell you how old they are.
Draughts
Draughts come from more places than people expect. Worn gaskets, dropped hinges, a gap between the frame and the wall, a missing seal at the cill and badly set locks can all do it. Some are cheap to fix. A hinge adjustment or new gasket costs little, whereas a gap between the frame and the brickwork often means the whole window has moved, and the sensible fix is replacement.
A simple test: hold a lit candle or a strip of tissue near the edges on a windy day. If it flutters at a spot you can seal, fix it. If the whole sash flexes when you push it, or the corners have separated, replacement is the better buy.
Rotten or damaged frames
Timber windows get soft at the bottom rail and cill first, because that is where water sits. Small patches can be cut out and repaired. Widespread rot cannot. uPVC frames do not rot, but they can warp in strong sun, yellow with age, or split at the welds. A cracked weld lets water in and is rarely worth repairing on a frame that is already old.
If you decide on new windows, the main options are a uPVC casement window for a standard opening and tilt and turn windows for upper floors and flats.
Ask the installer to explain what is wrong before they quote. If the diagnosis is vague, or every window gets the same remedy, get a second opinion. Costs vary, but a candid answer is the sign of a good firm.
What suits Hampshire homes
Many Hampshire homes were glazed in the 1980s and 1990s, and misting is a common complaint from that period. If you have a house full of the same age of window, compare the price of new units for every window against the price of new frames. When most frames are also tired, full replacement can cost less over the next ten years than patching one pane at a time. Salt air near the Solent speeds up hardware wear, which is another reason to look at the whole window.
Once you know what you need, the double glazing replacement cost guide breaks down the price of each route, and our warning signs checklist helps you survey the rest of the house.
How to decide between new glass and a new window
- Check the frame first
Open and close the window and look for warping, splits, soft timber and hardware that no longer works.
- Find where the fault is
Mist between the panes is a glass fault. Draughts and sticking sashes are frame faults.
- Test for draughts
On a windy day, hold a tissue near the edges and note where it moves.
- Count affected windows
If most windows show the same fault, compare the price of units against new windows for the whole house.
- Get written quotes for both routes
Ask for a price for new units and for a replacement window so you can compare.
Frequently asked questions
Can misted double glazing be repaired?
Some companies offer to drill and clean the unit, but the seal has failed and the result is rarely lasting. Most installers recommend replacing the sealed unit.
How much does it cost to replace a misted unit?
As a guide, a few units in sound frames cost about £150–£600, depending on size and glass type.
Why are my new windows still draughty?
Draughts from a new window usually come from fitting, such as gaps round the frame or poorly set locks. Ask the installer to check and adjust.
How long do sealed units last?
Many last 15 to 25 years, though quality and exposure vary. The seal is the part that fails first.
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