Surveyor Adam Stimpson AssocRICS takes a look at misty double glazed windows.
Double glazing improves the energy performance of windows by trapping air or specific gases in the space between the two layers of glass. For the insulating qualities of the windows to be maintained, it is essential that the air trapped between the panes is dry and that the unit remains entirely airtight. Poorly designed or manufactured seals will deteriorate over time, particularly if exposed to sunlight or simply due to age. When the seals breakdown, it enables moist air to leak in between the panes.
This becomes apparent as any moisture entering the panes condenses and leaves a misty fill. (Which can sometimes feed mould growth).
As a result, the windows thermal performance will be compromised, and the unit should be replaced, certainly before the onset of the colder winter months. It is worth noting this doesn't mean the replacement of the whole frame, which, as long as it is in good condition, an approved glazier will be able to replace just the blown glass unit.
The replacement of misted double-glazing is work exempt from Building Regulations and, importantly, will re-establish the window's energy performance reducing energy bills and noise resistance.
It is worth checking whether your current windows have a warranty rather than paying for any repairs!