Windows & Glazing

How to tell if double glazing has failed

Published 3 Jun 2026

What this video covers

How can I tell if my double glazing has failed?

The tell-tale sign is misting or fogging between the two panes that you can't wipe away. The seal has gone, so the insulating gas has escaped — but usually only the glass unit needs replacing, not the whole window.

In this video

  1. 0:00 The short answer
  2. 0:14 Misting between the panes
  3. 0:28 You'll feel it too
  4. 0:43 Usually just the glass needs swapping
  5. 0:58 What this means for you