Double Glazing Condensation question

[Chris Knight]

Many of the double glazed windows in our house have developed condensation problems between the panes of glass. I think they are all sealed units but over the years, I guess the seals have deteriorated. The window frames are Iroko.

I wonder what the best way to deal with this issue is? I don't wish to do the work myself especially but I should like to know if I need to replace all the glass, or whether the sealed units can be dried out and resealed in some way. I am pretty suspicious of the whole window industry and would like to know a little about it before picking up the phone!

 

[Woody Alan]

Chris

I would have thought the chances of getting the unit out intact enough to even attempt to do remedial work are slim to impossible. I don't think there is anyway to repair them economically because the whole units seal is suspect. Failure in wood frames is much more common because the unit is in contact with the frame as opposed to plastic where the unit is pretty much floating and retained by the trim.
If you do replace the unit make sure that whoever makes the unit makes it for a wood frame, a resin rather than silicone sealant should be used as this is much more resistant to breaking down.
Even if you could dry out the unit inside and replace the dessicant it is likely that the inside of the glass will now be stained fro the condensation which usually forms in patches during the day depending on sun position/temperature.

Alan

 

[Paul Chapman]

Chris, this is a very common problem. I have a few UPVC ones where the same thing has happened. Basically I think you will need to change the glass for some new units. At least with wooden frames you have that option - with the UPVC ones it probably means new windows that will similarly deteriorate after a few years.

The other problem I've come across with UPVC ones is that the hinges seem to fail very easily.

Cheers :wink:

Paul

 

[Neil]

Commiserations, Chris, I have the same problem. I don't think you have much option but to replace the affected units - this is what I've done in the past. As Paul says, at least this is an option with wooden windows!

My house has double-glazed six-over-six sash windows, so a total of 20 X 12 = 240 glazed units :shock: I'm starting to lose count of the number of units which have blown - when I get around to replacing them I'll certainly check out the resin system which Alan mentioned. Having said that, I'm tempted to single-glaze the lot! I think you can get little plastic pegs to lift the units off the rebate at the bottom, too.

Cheers,
Neil

 

[Woody Alan]

Paul

At least with wooden frames you have that option - with the blxxdy UPVC ones it probably means new windows that will similarly deteriorate after a few years.

I am a little unsure that I am understanding you correctly, it is dead easy to replace units in upvc windows takes 5-10 mins if you have one to hand to swap with. Perhaps you are referring to an older system?

http://www.impactglazing.co.uk/technical_info.php
Very informative further down it mentions about not using silicone units in wood.

Alan

 

[Paul Chapman]

I am a little unsure that I am understanding you correctly, it is dead easy to replace units in upvc windows takes 5-10 mins if you have one to hand to swap with. Perhaps you are referring to an older system?

The problem is that over the years specifications have changed, such as the thickness of the glass and air gap, so it's not always possible or desirable to replace like with like. And some of the UPVC frames are not very good and have a limited life.

The trouble often is that when you buy a house you are stuck with what's fitted and it is too expensive to replace the lot so you end up doing what is affordable. Like most things these days, double glazing is promoted as the best thing since sliced bread but a lot of it is unsatisfactory.

Cheers :wink:

Paul

 

[Chris Knight]

Thanks for the replies everyone. I shall make sure to get the resin sealed variety as Alan suggests.

I haven't counted all the windows Neil, I don't think it is as many as yours but I know the wallet will feel a lot lighter afterwards

 

[Woody Alan]

The problem is that over the years specifications have changed, such as the thickness of the glass and air gap, so it's not always possible or desirable to replace like with like. And some of the UPVC frames are not very good and have a limited life.

The trouble often is that when you buy a house you are stuck with what's fitted and it is too expensive to replace the lot so you end up doing what is affordable. Like most things these days, double glazing is promoted as the best thing since sliced bread but a lot of it is unsatisfactory.

It's not always easy coming up with the right answer is it? what to do for the best. It did occour to me afterwards that you may have had the front install "security" taped unit fitted which some companys were flogging, always seemed a bit daft if you needed to replace glass.
It took me ten years in this house before I could afford to change the windows putting up with one or two misty units in the old wood, but I have to say I don't regret it, sound insulation, extra warmth and none of that painting nonsense. But yes the lifespan of plastic windows is nowhere as long as first thought, and I live in a modern 1964 house so style obviously doesn't come into it or I may have thought more about other alternatives.

Alan

 

[mahking51]

Chris,
I have had the same problem as you and am slowly learning how to deal with it.

First off its almost impossible to get the old units out of a wooden frame intact, I saved 4 out of 10 to use in a cold frame.

Do shop around, I found huge price differences for the new units, I now pay around £14 to £20 each for mine.

After a couple of my newly installed ones failing after a year I found that it was my fault in that you MUST overdo the sealant (silicone) bigtime around the frame so that it squirts out with no voids on the inside; THEN put more sealant under the retaining beading, install beading and leave for a couple of days.
When dry it is very easy to do a neat job with a razor blade and blade scraper to clean up.
Done like this they have been trouble free now for over two years.

Regards
Martin

 

[suprasport]

Hi, this is my first post. It was going to be about thanking you all for the information i have taken for the last couple of months but i will save that for later. I have been in the double glazing industry for 20 years and much of what has been said is true, but to get the units outs just prise them out with a chisel or scraper working your way along, although it is highly unlikely you will succeed as for repairing them that is a definite NO. buy new ones you should be paying no more than £20 per square meter. allthough most companies have a minimum price for very small units. Do not let any silicone contact the resin that seals the units as it breaks it down, make sure the units are taped with gaffer tape after they have made them all around the edge, in some ways this does protect from silicone getting in contact with the resin if used, also ask the supplier for some plastic glazing packs and place these around the edge between the glass and the frame, one in each corner. this will keep any damp away from the unit. make sure the rebate is well protected/varnished and if possible leave to small weepholes on the underside of the bottom glazing bead. If you can do this yourself you will save a fortune as the companies love charging for this type of work as it is necessity rather than choice :evil:
Hope this helps

 

[mahking51]

Suprasport,
Thanks for that, I did not know that silicone is not a good idea. What sealant would you recommend please as I have more to do when the weather perks up a bit.
Oh, and by the way - welcome to the forum
Regards,
martin

 

[Chris Knight]

Martin and Suprasport (Welcome to the forum btw!),
Thanks for the additional info - I shall definitely price the job both as a DIY and commercial effort to see what I might save.

From Suprasport's suggestion about plastic glazing packs, it sounds as if the units need to be made smaller than the frame by some amount - is there a standard?. Also, should I expect the supplier to seal the units with gaffer tape or is this a DIY thing?

 

[suprasport]

the unit should have a 3-5mm clearance from the frame dependant on the beading used, the gaffer tape should be done by them. but its a 2 minute job to do it yourself, the point being though if they are any good they will do it anyway :wink:

 

[llangatwgnedd]

Hi Chris, this thread has taken me back to my old glazing app. days .

Double glazing was slowly introducing it self to the uk market and at the time we could only order sealed units from Pilkingtons or their recommended suppliers and took ages to come through.

As it was only wood frames and still have to see a metal window frame for D/G units they would insisted on non setting putty (pipper to apply just like putting your hand in dog muck :? ) and each unit to sit on and surround on rubber pads as the expansion and contraction where the downfall of these units/frames.

Been a while since glazing (35yrs) but find out about vacuum sealing I believe the`y are a better unit, but don't quote me :?

 

[llangatwgnedd]

BTW, if the installer comes along and wedges your transom up with plastic wedges on top of your sealed unit tell him to take a hike as this process is the most common cause of failer

 

[Anonymous]

the point being though if they are any good they will do it anyway

Absolutely! This is where the difference between D/G companies become apparent, the cutting of corners on the units is one, (it's also there to stop the fitters cutting their hands! DAMHIKT!)
Other things to consider when the quote is offered that seems a great price is the use of mechanically fastened transoms etc rather than welded, so prone to moving and reliant on silicone to prevent water penetration, external beading and cheaper profiles that lose their whiteness and become brittle after a few years, no ali or steel strengthening in longer profiles, cheaper locks and fittings...
As for the hinges being weak, often this is down to poor fitting practices Side hung lights should be toe and heeled, so the weight is thrown back to the bottom hinge, much the same as a L&B door, so the packers are placed on the bottom corner by the hinge side, and the top closing stile, so on a diagonal. This keeps loading weight off the bottom closing edge of the light so it doesn't take too much weight and strain the hinge. The same applies for doors.
I've sorted out loads of D/G doors and windows that have dropped and start to catch or the locks don't align any more because of this.
Doesn't help with your misted units Chris, but things to consider if anyone out there is having problems either with a potential purchase, or a recent fit...

Andy

 

[Chris Knight]

SP, Andy,
Thanks, it looks as though I shall have to look out for quite a few things!