Double glazing units failing

[Mike Lane]

I had some double glazing units replaced by a local firm when I moved into my house about 8 years ago. The ones I replaced had obviously failed as condensation was forming on the inside.

Now the same units have become misty again - no condensation as such, just a faint film on the inside which looks very ugly (particularly in sunlight). A glazier who came to look at them told me that this was quite normal and that one couldn't expect any double glazed units to last more than 8 to 10 years. Is this true? Are there cheapo units around that will fail more quickly? (Or conversely more expensive ones that last longer?).

I would appreciate any advice before I go ahead and replace them again. Thanks

[Stuart Noble]

The "faint film" you're getting is also condensation but, unless it's between the 2 panes, there's probably nothing wrong with the units. If it's only just started, it may be to do with the strange weather we're having. I'd reserve judgment until that wind gets back to SW and brings us some warm stuff

[crb]

If my experience is anything to go by, it is not condensation per se, but the result of condensation causing salts to be leeched from the glass, leaving a cloudy film. This film cannot be removed (at least, not easily) even after getting access to the inside pane. My understanding is that this is not uncommon with any double glazing that is not truly hermetically sealed, and such units commonly have a life of around 15 years before this clouding starts to happen - although I have some units over 25 years old that are still clear.

crb

[Mike Lane]

On Thu, 17 Apr 2008 09:47:20 +0100, Stuart Noble wrote (in article ):

Sorry, I didn't make myself clear. The film is between the two panes. If it were not I could simply wipe it off (i.e. clean the windows!).

I was told that the space between the panes was originally evacuated, and when the vacuum fails (after 8 - 10 years) the filming occurs and the unit needs to be replaced. If this is true I would be tempted to get rid of the double glazing and go back to normal windows that at least could be cleaned properly.

[Stuart Noble]

I don't think that gap was ever a vacuum. I've never had this happen on dg units, even on one that I accidentally cracked. That used to steam up very slightly in the corner where the crack was, but never got any worse.

[Harry Bloomfield]

Stuart Noble was thinking very hard :

25 years old and no such problems here. The gap is not a vacuum, but filled to a similar or slightly less pressure to normal atmosphere. Were it a complete vacuum, then there would be about 14 pounds per square inch of pressure on the glass - multiplied by the area of the glass. The seals should not fail after 8 to 10 years, they have an indefinite lifetime, but most companies seem to provide a 10 year guarantee - then disappear. Check the terms of your guarantee.

I have heard of one DIY solution, if you are completely stuck. It involves drilling holes in the seal between the panels in two opposite corners and circulating warm dry air through for some days, before re-sealing. From memory the method used silica gell in a sealed box, with a fish tank pump to circulate the air via small pipes in a closed loop through the box, pump and window. Then re-seal the holes with silicon sealer as you withdraw the pipes with the idea to leave a slight vacuum between the panes. It is supposed to be very effective and the slight vacuum helps pull the seals in.

[Mike Lane]

On Thu, 17 Apr 2008 20:52:04 +0100, Harry Bloomfield wrote (in article ):

Yes of course - I hadn't really thought about it properly. The panes would never stand the pressure. (I should have remembered the 'collapsing can' experiments that science teachers loved to demonstrate in the old days :-)).

I don't think that would help. The misting is definitely not condensation - it's more like the haze one gets on the inside of a car windscreen that's not cleaned for a few months - not very obvious until it gets into direct sunlight, when it looks horrible.

[normanwisdom]

DG units nearly all fail sooner or later. 25 years is possible but rare. 15 nearer the average. Nowt you can do about it except replace them.

cheers Jacob

[jim]

AIUI - the main problem is how to effectively seal two panes of glass together *forever* given that they have to be economically knocked up in workshops to effectively any size. The "metal" strips visible on the inside of a DG unit contain silica (shake an uninstalled DG unit and you can hear it rattling) to try to prolong the life before said effects appear. Worse if more south facing as days & days (maybe hours this summer!) of heat stress (differential expansion, contraction etc) eventually break the "seal" around the edge and allow either moisture in and/or your precious Argon out.... no repairs work, dump 'em and buy more.... someone must have calculated the "whole of life" environmental cost of all this - is it really worth bothering with DG at all??

Jim

[Andrew Gabriel]

My first DG units had no failures in 25 years. They had to be replaced because they had been fitted to the old sash boxes which had gone rotten.

A common cause for failure is the sealed units sitting in a puddle of water inside the frame due to poor frame drainage. In cold weather, this freezes and wrecks the seal. Modern uPVC frames don't attempt to seal against the glass (would require more highly skilled fitters). They rely on drainage holes to allow water which gets into the frame to run out. Check these aren't blocked, and when you take the units out for replacement, make sure the channels under the unit are clear of debris so water can run out.

Early frames often used a mastic seal against the glass which was completely waterproof, and sealed units in those tend to have a much longer life than in uPVC frames as the unit edges remained dry.

[Mike Lane]

On Sun, 20 Apr 2008 09:47:42 +0100, Andrew Gabriel wrote (in article ):

Thanks. I'll try to do that when the fitter comes to fit the replacements. (I'm not doing it myself I'm afraid :-).

[info]

go

get a quote for replacement double glazed units, argon gas filled seem to be the best as they last upto

35 years, its what everest and anglian fit as standard.

[Stanley]

Hello Mike.

I usually think of this problem being with wooden frames but a 5' square window in our UPVC sitting room window has done the same.

Might have been the earthquake which was 3 days before I noticed the misting. It gave us a good shaking here.

I am having the unit replaced as the frames are OK. They are about 14 years old and were a cheapo deal as I expected to have to move again within 2 years ..... but didn't. The cost will be about £250 to 300. It has to be toughened glas cos it's a low window sill.

Needless to say the original firm seems to have disappeared :)

Awful lot of spam here these days.