Condensation Inside Double Glazing in Dunstable: Repair or Replace?

First, check where the condensation actually is

Where the moisture sits tells you whether you have a fault or just a damp morning. Run a finger across the glass on both sides before you ring anyone.

• On the room side: this is a humidity and ventilation issue in the house, not a faulty window. Common in bedrooms, kitchens and bathrooms in winter. Open trickle vents, use extractor fans and avoid drying washing on radiators.
• On the outside: usually seen on cool, still mornings in spring and autumn. It means the glass is insulating well and keeping heat in. It clears on its own.
• Between the panes: the perimeter seal has broken down and moist air is getting into the cavity. This is the one that needs fixing.

Why sealed units fail

A double glazed unit is two panes bonded to a spacer bar, with a desiccant inside the bar to absorb any trace moisture. Over time the edge seal degrades, the desiccant becomes saturated, and the cavity starts to fog. Most units last somewhere between 15 and 25 years, though south facing windows that take a lot of sun often go sooner because of repeated expansion and contraction.

A lot of the housing around Dunstable, Houghton Regis and Leighton Buzzard was fitted with uPVC double glazing in the 1990s and 2000s, so many of those units are now reaching the end of their life. Blocked drainage slots in the bottom of the frame speed things up too, because the edge of the unit ends up sitting in water. Exposed elevations facing the Downs tend to take more wind driven rain, which does not help.

Once a unit has failed it also loses any argon gas fill and some of its insulating performance, so the room will feel slightly colder near that window.

Can it be repaired, or does it need replacing?

There are services that drill small holes in the glass, dry out the cavity and fit vents or plugs. This can clear the view for a while, but it does not restore the original seal or the gas fill, and the misting often returns. Any mineral staining left on the inner faces of the glass usually stays. We would treat it as a short term cosmetic fix rather than a repair.

The dependable fix is to replace the sealed unit only. The beads are removed, the old glass is lifted out, and a new made to measure unit is fitted into your existing frame. It typically takes 20 to 40 minutes per window once the unit has been manufactured, with very little mess and no redecorating.

A full replacement window is worth considering when the frame itself is the problem. Signs include:

• uPVC that is cracked, warped or badly discoloured
• Rotten timber or corroded aluminium frames
• Hinges, locks or handles that are obsolete and cannot be sourced
• Draughts or leaks coming through the frame rather than the glass
• Several failed units in old frames where the combined glass cost approaches the price of new windows

What it tends to cost around Dunstable

Prices depend on the size of the pane, the glass specification and how easy the window is to reach. As a rough guide locally, a small to medium standard clear unit supplied and fitted often falls between about £70 and £150. Larger panes, toughened safety glass, obscure bathroom glass, leaded or Georgian bar designs, and big patio door units can run from roughly £150 to £350 or more.

Upstairs windows that need to be glazed from outside, or anything above a conservatory roof, may add access costs. Doing several units in one visit usually works out cheaper per window than one at a time.

Before paying for anything, check your paperwork. Many installations carry a 10 year guarantee on the sealed units, and if your windows are within that period the original installer may be responsible. If the units are being replaced anyway, it is a sensible moment to upgrade to low emissivity glass with a warm edge spacer, which usually adds little to the cost and improves heat retention.