Double Glazing advice

  Esc4p3 21:41 30 Jan 2011


Our double glazing has been installed for 10 years or so and looks to be in good shape. Having said that we get the feeling that the glazing is not working as well as it should as our house seems to be getting colder. The back bedroom in particular seems to be getting a draft from somewhere.

Do you have to maintain double glazing, does it wear out? Are there any experts out there who can help me look for signs of wear and tear, and how long should double glazing last.

Any advice greatly received.

  Forum Editor 22:32 30 Jan 2011

Double-glazed units typically have an effective lifespan of between 10 and 25 years.

How long they last depends on many things - how ell they were made in the first place, the way they are installed, and environmental conditions.

If you're getting a draught in a room the cause is more likely to be a failed or ill-fitting frame seal, rather than the unit itself. When the units fail you'll see a faint misting inside the unit itself, indicating that the seal between the two pieces of glass has failed, and is allowing air inside. When that happens there's nothing you can do, the unit must be replaced.

  birdface 22:52 30 Jan 2011

Maybe you need cavity wall insulation.
You could get it done free from the council but not sure if it has been stopped recently.
Or maybe the Mastic filler around the outside of the windows has shrunk or decayed.

  jakimo 01:37 31 Jan 2011

Do not be in to much of a hurry to replace your sealed units,as the outside temperature (sever cold e.g)can have a bearing on the efficiency of double glazing units, (Scandinavian Countries install triple glazing to overcome this)

  morddwyd 07:34 31 Jan 2011

I can confirm the FE's comment that in the event of failure you will see condensation between the two glass panes.

I had one go just like this a few years ago.

It took them something under a minute to replace it!

Very unlikely that they would all go at once.

  Esc4p3 09:10 31 Jan 2011

Thanks for the replies. There is no misting inside the unit, we did have that with one unit and it was obvious the unit failed. I think it is more likely the frame seal or the mastic filler around the outside of the windows. We did get a reputable fitter who manufactured their own units although in the last year or so they have gone out of business. Is there a test I could do to further investigate or is a matter of close inspection? If the frame seals are not fitting correctly or perished are they replaceable, is the window 'mounting' adjustable to make the window fit better? Or do I just call in the experts!

  Esc4p3 09:11 31 Jan 2011

Meant to say, I think we have cavity wall insulation as there are drill holes in the wall and white bits coming out of the air vents in the loft space. The house was built in the early 80's by McLean (I think)

  bjh 09:25 31 Jan 2011

Close inspection may bear fruit. A candle will help locate draughts (mind the nylon curtains, though). Mastic is easy to replace; there is often movement between the frame and the structure of the house. This is normal, and doesn't mean the units are failing, or that the house is falling down ;)

If there is a wideish gap at any point, it is often worth removing the older sealent (pull it/sharp knife may help) and to replace it with a good solid bead of mastic that squeezes itself deep into the frame/house gap. Better for insulation that way.

Remember that, for all its insulatory properties, double glazing is significantly improved by closing curtains at night.

  Forum Editor 09:33 31 Jan 2011

in position are easily replaced, but it's very unlikely that these are the culprits. It's more likely that the problem is the frame seal, as I mentioned in my first post.

If you use a mastic to replace the seal, make sure you use the non-setting type, otherwise you'll be back in the same boat very quickly.

Thermal movement differentials between different materials are commonplace and nothing to worry about.

  Esc4p3 09:42 31 Jan 2011

Thanks FE. Just to clarify, so that I know what you mean. Is a frame seal:

The seal between the window and the double glazing unit


The seal beween the window and the windows frame

I am not a very savvy DIY'er, hence the noob questions!

  birdface 11:08 31 Jan 2011

It is The seal between the window and the double glazing unit.
If this had a fault your windows would mist up inside.
So the problem is probably the mastic fitting on the outside of the window..
Mind you having seen some cowboy builders on the TV I would have a look under the sill inside and outside just to make sure they filled the holes up.
Check the mastic filling on the outside it should be about quarter of an inch thick or just a bit more.

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