Failed double-glazing units

Feb 17, 2009 4 Replies

Our double-glazing is about 16 years old, and in the last 6 months three units have failed with condensation inside. All the failed units are south-facing - presumably the more extreme heating cycle weakens the seal eventually.


1) What's a reasonable lifetime for a DG unit?
2) Would K glass help to extend the life of a south-facing window?
3) Can I replace the units myself like for like, or does a FENSA bod have to do do (or approve) the work?

I think how well they're assembled in the factory has a greater influence rather than the glass. You see a lot of big windows that have been sealed when lying flat which results in concave windows. This not only looks naff but I think causes them to fail more quickly than those that are sealed upright. [1]

Tim

[1] I could be talking boll*cks but it seems palusible to me. ;-)

16 years isn't too bad for the first failures to show up. Good quality units correctly fitted would last longer.

No. If anything, it would make it worse because the differential expansion would be larger.

You can do it yourself. Some glaziers may remake the units using your glass for you, providing the safety aspects of the glass meet current regs, and the glass can be cleaned up.

When the units are replaced, check and clean the drainage channels under the units, so that water that inevitably gets into the frames can drain out without collecting. A common reason for failure is the units end up sitting in a pool of water in the frame which isn't draining away, which damages the seals over time, and pretty instantly if it freezes. They should be lifted clear of the water drainage channel.

In article , Andrew Gabriel writes

On wooden windows I've taken to back filling the gaps around the DG units with neutral cure silicone. I thought the risk of trapped moisture was too great so made it so it can't get to the unit seals.

Not too difficult, on my older panes I removed the rubber seal from the inside which then allowed the outside seals to pop out easily.

Took the panes out to measure, I had leaded glass which made it more difficult.

Geoff Lane

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