Misted double glazing? Replace it with a security unit

Why does double glazing mist up?

A sealed unit is two panes held apart by a spacer bar and sealed round the edge. The spacer holds a drying agent that soaks up moisture. Over time the edge seal can fail, the drying agent becomes saturated, and moisture condenses between the panes. The unit also loses some of its insulating value.

Can a misted unit be repaired instead?

Some services drill and dry the cavity, which can clear the mist for a time but does not restore the seal or any gas fill. Replacing the unit is the reliable fix, and it is the point at which the glass can be upgraded.

What does a laminated replacement cost?

Misted unit replacement with laminated glass usually costs £125 to £395 plus VAT (£150 to £474 inc VAT) per unit, depending on size, glass type and access. Several units replaced in one visit cost less per unit than separate visits.

How is it measured and fitted?

The glazier measures each unit and the frame rebate at the survey, and the new units are made to order. On the day the beads come off, the old unit comes out, the new one is set on packers and the beads go back. The frame, hinges and handles stay as they are.

What else can be upgraded at the same time?

• Laminated inner pane for security, or laminated on both sides for more
• Low-emissivity glass and a warm-edge spacer for better insulation
• Acoustic laminate for busy roads
• Obscured glass for bathrooms and front doors
• Toughened glass wherever the unit is in a critical location

Sources

• Do I need Building Regulations approval to change my windows? (Warwick District Council)
• Approved Document K: protection from falling, collision and impact (GOV.UK)

This guide is general information, not legal advice. Rules differ between England, Wales, Scotland and Northern Ireland; check with your council, building control or insurer where it matters.

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