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?

--
Reentrant

Reentrant wrote:
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?

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. ;-)

In article ,
"Reentrant" writes:
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?

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

2) Would K glass help to extend the life of a south-facing window?

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

3) Can I replace the units myself like for like, or does a FENSA bod have to
do do (or approve) the work?

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.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article , Andrew Gabriel
writes

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.

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.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

Reentrant wrote:
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.

3) Can I replace the units myself like for like, or does a FENSA bod have to
do do (or approve) the work?

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