Misted or Blown Double Glazing, Repair or Replace?

Misting between the panes means the perimeter seal of the sealed unit has failed and moist air is getting in. Once that happens the desiccant in the spacer bar is saturated and the unit will not clear itself.

The decision is simple in principle: if the frame and hardware are sound, change the glass. If the frame has failed too, change the window.

Why units fail here

• Age, as most sealed units are designed for a service life of around twenty years
• South and west facing elevations, where heat cycling works the seal hardest
• Standing water on cills where drainage slots have blocked
• Coastal exposure and wind driven rain
• Poor original installation that left the unit sitting in water

Does defogging work?

Drilling and flushing a unit removes the visible mist for a while but the seal is still failed, the gas fill is gone and the thermal performance does not come back. We do not offer it, because within a couple of years most treated units mist again.

Replacing the unit only

On a sound frame the glass is replaced in place, usually in under an hour per opening. It is the moment to upgrade specification: low emissivity coating, argon fill and a warm edge spacer cost very little extra and improve the window measurably.

When the whole window should go

• Multiple units failed across the same elevation and the frames are aged
• Cracked or distorted uPVC, or rotten timber at the glazing rebate
• Beading that will not hold a new unit securely
• Frames still single glazed or with obsolete hardware

Questions people ask