Double glazing misting problem - but not all the time.....

[DIYNotIan]

Hi

I've never had this problem before so know little about it....

We moved into a house last year and noticed some of the windows mist up in between the two panes of glass. We've come to accept that and from what I've read the only real solution is to have the glass replaced and new seals. However, another couple of windows have started to do this now - BUT the misting comes and goes.

What I wondered was whether there is any cheap and cheerful way to seal the window while it is not misted to prevent the moisture from re-entering? From a totally naive guess point of view, I wondered whether sealing the seals (!) with some kind of clear silicone would work. Or are there products already on the market for this?

Any advice would be great.

Cheers

Max

 

[Burnerman]

Sad to say Max but if the double glazing unit has failed, then its failed.....the moisture may well disappear for a while but it will return, and after a while there will be traces all over the glass insides.
Happens all the time.....
John

 

[freddiemercurystwin]

This question arises on the Forum regularly, nothing will work as a permanent fix other than replacing the double glazed units. They have an expected life of about 10 years, when they're blown they're blown.

 

[DIYNotIan]

Thanks for letting me know guys. I did read up a bit the other day and reached the conclusion that replacement was the only decent option.

I just posted this because I wasn't sure if the solution might be different when the misting comes and goes (rather than being there permanently).


Cheers for the info

Max

 

[freddiemercurystwin]

It comes and goes because the unit is drying up and then condensing depending on the atmosphere around it as effectively it is open to the atmosphere, nothing unusual in that respect.

 

[DIYNotIan]

That's where I struggle to understand why using some kind of mastic or silicone would not work. If the unit has dried out, and if silicone/mastic/??? can provide a water tight seal, then how does moisture re-enter?

Please note - I'm not saying I think I know best or that my thoughts are correct.... I'm just thinking allowed and trying to get it clear in my head.


Thanks for all you time

Max

 

[freddiemercurystwin]

Nobody has said it will not work temporarily, but your 'repair' will fail.

The problem is with the seal of the double glazed unit not the seal between the double glazed unit and the frame. You would need to stop vapour entering the frame of the window. Even if you were to remove the double glazed unit you need to somewhow identify the pinhole where vapour is entering the sealed unit and it will also be difficult (read impossible) to remove all of the vapour from between the panes before you 'seal' it up again.

 

[slpj]

Well, actually, I think sealed units can be repaired. I am confident that I have in fact repaired one. I discovered this quite by accident, and it relates to the posters question about why misting only sometimes.

As to it being worth it, that depends on the extent to which any water damage is evident on the inner surfaces of the glass, and or, if it bothers you.

Here's my evidence.

First a re-cap.

Sealed DG units are 2 sheets of glass separated by a water absorbent strip (desiccant), and stuck together by a supposedly water/air tight glue/mastic/sealant.

This gives a window unit with enhanced thermal insulation properties, when compared to a single glazed window.

The air gap within the unit prevents excess heat transference between the 2 sheets of glass, because air and other suitable gases, are poor heat conductors. Argon is said to be the best for domestic use.

After a period of time, -- not fixed--, water vapour penetrates to the inner space between the glass sheets, and the desiccant eventually reaches a point where it can't absorb any more water at all. That is because it is at the limit of its capacity to hold water. It’s saturated. At that point, when the temperature is right, the water becomes a gas, and when the temperature drops again, the water becomes droplets again (condenses), on the coldest surface of the 2 sheets of glass. --- Usually the outer of the sheets.

Hence misted Windows.

If left long enough this will result in irreparable damage to the inner the surface of the glass sheet(s).

There might be one or a combination of causes for the failure of the sealed unit. Often simply age of the sealant is a big factor.

But remember, they were NEVER perfectly sealed in the first place, as no sealant is 100% effective. Hence a small amount of water vapour gets IN over time, just as Argon gas, air, or other gas will leak OUT over time.

The problem of water penetration is often exacerbated by poor installation and or design of the window units into the frame. Insufficient/inadequate spacing blocks/drainage etc, which leave the units lower edge sitting on water. Eventually the sealant is breached.

Often, as stated on other sites, the reason for failure is visible once the unit is removed. Often one can see water in the lower channel, and its cause is pretty obvious. Other times not.

So what to do about it?

Well how about drying out the desiccant, so that it can once again absorb the water?

It only has to be below saturation point to be effective again; ---- As long as steps are taken to prevent excess (or any if possible) water, from getting at the (leaking) sealant.

You can't stop the air-borne atmospheric water, but you can replace rubber seals, and make sure that drainage is working and adequate, and that the units are spaced well above the likely level of water in the lower channel in which the unit sits. Thus preventing the next rainstorm from bathing the lower edges of units in water. And I believe it is the lower edges that are the most likely to be the cause of most of the water penetration, --- unless water is getting behind the rubber seals from the top of course.

Now to the point.
I removed a so-called failed sealed unit, and sure enough it was sitting in a degree of water. The external rubber seals had moss on their faces where they meet the glass, and the drainage in the window frame was partially blocked. There was sufficient water for the lower edge of the unit to be sitting in liquid water. Even though the spacing blocks looked adequate, and were of the bridging type, they could have been at least 3 mm thicker, thereby raising the glass above the water, and still allowed easy installation.

At this point I was just inspecting with a view to replacement of the unit, since it was misted. So prior to ordering a new one I cleaned up the window frame and seals, cleared the drainage, and increased the spacing blocks. I added a 2mm block.

Meanwhile, I had left the sealed DG unit lying on a lawn in the hot sun. When I picked it up, I almost burned my hands. The lawn now has a brown burnt patch the size of the sealed unit. It had not occurred to me that it would get so hot. Yup, stupid.

Anyway, I cleaned up the edges of the unit and put it back in.

At this point there was no misting visible on the glass, whereas beforehand there had been. ---- I expected it to return.

However, several week later, no misting.

Here is where I start guessing/theorising.

The heat from the sun, whilst the unit was lying on the lawn, both raised the temperature inside the unit and the pressure. The water turned to a gas, and due to the pressure was forced out of the unit.

As I said I almost burned my hands as I picked up the unit by the edges. So it occurs to me that maybe the aluminium desiccant strips got so hot that they dried out the desiccant, thereby returning its ability to absorb the small amount of water that normally gets past the rubber seals and the sealant.

Presumably, eventually, sufficient water WILL get back in, and once again saturate the desiccant. BUT that could take a year or 2 or 4 ???--- Especially as I have improved the drainage, renewed the rubber seals and increased the lower spacing.

So, is this repaired? Well I now have a mist free DG sealed unit where once it was misted. That in my book is a repair, and was FREE except for my time.

As for the other property of the unit, the thermal insulation; Well unless the unit is allowing the free circulation of air, -- which it is not - or is pretty well full of water, - which it is not - then it is probably as good as it was when first installed as regards its thermal insulation properties. But I am not sure how I can measure or prove this other than taking the temperature of the inner and the outer glass sheets.


On reflection, I now think that there may be an even better way to repair the misted units.

1) Remove the unit.
2) Inspect and repair/renew/improve/ drainage, rubber seals, and add to spacing blocks as necessary.
3) Drill a hole just sufficient to empty ALL the desiccant silica gel balls out of each of the four aluminium strips. DO NOT PENETRATE THE STRIP THROUGH TO THE AIR GAP BETWEEN THE GLASS SHEETS.
4) Replace with NEW desiccant. It’s cheap enough.
5) Seal the drilled holes with suitable sealant to prevent the silica balls falling out, and to re-seal the unit.

6) DO PREVENTATIVE CHECKS ON ALL OTHER UNITS BEFORE THEY MIST, and most importantly BEFORE they are water damaged.

I even think that there may be a business opportunity in this, offering to do preventative checks on existing installations BEFORE they mist up.

I am going to use myself, and my own remaining window units as an experiment. Then who knows, this time next year I may be a “miwllionaire Rodney.”


OK Critics, what do you say?

 

[Alastairreid]

Great 1st post

 

[slpj]

I took another two DG sealed window units out yesterday. One was showing the first signs of misting, but has not suffered from any permanent water damage. The other has no signs at all, but I thought I would do as I said and try a bit of preventative maintainance.

I found exactly the same thing. Water has been getting past the external frame rubbers, and the sealed units were sitting just above the small amount of water in the lower channels. Obviously the sealant on the slightly misted unit is leaking, but to what extent is not clear, as it looks perfect.

But as I already said, it never is, and as someone else said, all it takes is a pin-hole.

That of course is the reason for the desiccant silica gel in the first place.

So I cleaned up the channels, cleared the drainage, cleaned the facing of the rubber seals where they meet the glass, and added an extra 1mm spacer on one frame and 2mm on the other.

Whilst I did this, I left a warm air dryer blowing at the sealed unit that was showing the first signs of misting, and then used a hair drier to ply hot air on all the edges to dry out the silica.

There was no misting when I put the unit(s) back in, and I'll wait to see what happens next.

Meanwhile the first one I did several weeks ago, is still fine and clear, apart from the small amount of water damage that it had already sustained before I "fixed" it. But this isn't that bad, so I am going to leave it for a while longer before I replace it, to see if my "fix" is really working.

But I am even more confident now, that it is.

I'm going to source a supply of silica gel balls, and take another unit out that is already water damaged, and look at the feasability of removing and replacing the desiccant in the way I described in my previous post.

But if the first unit stays clear after a few more weeks, --- if we get rain and shine ---, then I might just simply "dry out" the units as i am doing now.

What would really do it, is a temperature controlled oven, but I don't have acces to one.

Seriously I am beginning to see a business opp here. Think of all the millions of windows out there that are easy to fix with this method. Quick and effective and CHEAP.

There's essentially nothing wrong with the Glass (if it is not badly water damaged), the spacers, rubbers, -- or the sealant really, so it does seem odd that nobody has ever come up with this solution before.

OR, maybe it has been realised that this can be done long ago, and that it has been kept quiet to persuade people to either buy replacement units, or even replace the entire window frame and all.

 

[God]

Easy and cheap for you to do if you know what your doing, what you are doing is no different to the double glazing repair companies who pump chemicals into a broken down unit, if you set this up as a business and started traveling to do the repairs it would not become so cheap then, I could probaly supply a new unit for as much as you would charge to repair one

 

[crank39]

So I cleaned up the channels, cleared the drainage, cleaned the facing of the rubber seals where they meet the glass, and added an extra 1mm spacer on one frame and 2mm on the other.

Thats all well and good but what you have failed to do is find the leak in the hotmelt or 2 part polysulphide seal!

I replaced a blown unit today amongst other things, reason it blew was because it was sat on 24mm packers yet the unit was a 28mm, the inner pane had slid down effectively creating a stepped unit, this had obviously broken the seal, are you saying you would leave this other than dry the unit out, change the packers and clean the rubbers?

Good luck to you if you think you can make a business of it but somehow i think it'll fail (no pun intended)

 

[slpj]

There are seperate issues here.

1) is it a business opp?
2) does it work?

I'll speak to 2) first.

First and foremost, so far it is working. So the debate has to be set in that context.

After several weeks yes it works so far. I am in the waiting period. But the evidence is so far very positive.

As regards what other companies are doing, I am not doing the same. I am pumping in nothing, only removing the water. So it is zero cost and minimal effort. Even if I were to replace the unit I would still have to do all the other steps, PLUS go and collect or have delivered a replacement unit. I dont agree at all, that it takes less time to simply change the unit. If the unit is not yet showing any bad sign of water penetration, its only a matter of removal, cleaning and then replacement with the same unit. I assume that cleaning, clearing and inspection as neccessary would always be done? If not then I would be most dissatisfied.



A stepped unit as you describe is a different matter. However, if it took long enough to mist, and is not otherwise damaged, I cant see why you cant support both sheets of glass and re-seal. But in such a case I might well replace it. You haven't described the extent to which the water has penetrated and damaged the glass surfaces. So I am not really in a position to comment.

How often is it that a unit is so poorly installed anyway? And you make my point for me. Presumably the installation is not new and under warranty, hence you are called to do the replacement. So, why not advise your customer, that as it was improperly installed, it is quite possible/probable that all or some of the others were too. You can then do a preventative check and perhaps avoid more failed units as well as increasing your profit quite legitimately.

This talk of "blown" units, suggest a situation where sealed units suffer catastrophic failure and are impossible to re-seal. When in fact, as admitted in your post, by saying ----

but what you have failed to do is find the leak

--- leaks are NOT catastrophic at all, otherwise they would be easy to find.

No, it is a slow gradual process in most cases of water penetration through the imperfect seal. Hence there is no need to waste time attempting to find something that is too small to see. I cant see any reason, if a satisfactory drying method (and quick, if it is to be a business) can be employed, that the unit cant be given a coat of a suitable sealant and replaced. If there is no water damage to the inner surfaces, it could be good for a few or more years to come. Perhaps many more years.

2) Is it a business opp? Well that depends on ones attitude and vested interest I suspect.

At this stage, I am only pondering the possibility. Many a profitable venture (including at least one other of my own) has started in this fashion. Discovery, investigation, refinement and execution. I am at the investigation stage, because I see the very real possibility of refinement and future profit. I don't intend, or care to replace all others in the business, only exploit what seems to me to be a rather large hole in the market.

Business apart, at the very least, I and other suitably minded and able people, can pretty easily save a substantial amount of money if they do this for themselves instead calling on the services of a window repair company.

Removing double glazed windows and replacing them has a reputation of being a mysterious, and best left to the expert enterprise, when in fact it is not that complicated. Many people could do it if it were de-mistified (no pun intended either).

 

[crank39]

.........I cant see any reason, if a satisfactory drying method (and quick, if it is to be a business) can be employed, that the unit cant be given a coat of a suitable sealant and replaced.........

Just on these two points i think your business would fail.

Not knocking you AT ALL for thinking outside the box but lets look at it this way.

How would dry the units?
How could you guarantee its total dryness?
Can you actually dry desicant crystal to their original state?
What equipment would you need to do the above?
How would you remove a unit from a timber window where its been bedded on putty......without breaking it?

Assuming you can do all the above you then have to ask 'what would i charge' and 'is it cost effective' and on top of than the customer will want assurances and a minimum of a 5 year guarantee, something you'd get with a new DGU

 

[JohnD]

OK Critics, what do you say?

incredibly verbose.