I’m pretty sure the double glazing at home’s not working. Despite a consistent 45% humidity in the house I’m getting lots of condensation on the windows. The obviously blown units fell about the same temperature as the others.

Before spending a load of money that I don’t have is there a quantitative way of checking? I’m thinking IR thermometer to take the temperature of the inside pane. Any idea what it should be with outside temperature at 5c and inside at 20c ?

How old are the windows? Do they have a fensa guarantee?

I have had a bunch of units fail – slimline in sash and case and in veluxes ( all plenty old enough). ~they all got condensation between the panes not on the inside.

An IR thermometer may not reliably measure the temperature of glass as it disrupts the beam.

As above how old and are they fensa certified? They’re fairly simple the main thing that fails is the argon filled cavity and its not a particularly expensive repair for a skilled glazing contractor to do. The cost of having it repaired is offset by the energy losses of a failed unit. I would doubt they need replaced probably just the seals and a refill of the argon.

I have had a bunch of units fail – slimline in sash and case and in veluxes ( all plenty old enough). ~they all got condensation between the panes not on the inside.

This. I replaced around 5 windows that failed at our last house.

Condensation on the inside would point to not enough heating/too much moisture. Have you been drying clothing inside?

Windows are at least 20 years old based. Some are obviously blown – condensation inside the unit. Relative humidity of 45% in the house with 90% outside and inside temperature of 20c when the outside is 0c fit with there being enough heating and ventilation (and no clothes drying).

@airvent – I didn’t realise that units could be re-filled and re-sealed, thank you for the idea.

An IR thermometer may not reliably measure the temperature of glass as it disrupts the beam.

You’re right about the unreliable measurement, but they don’t ‘beam’ they measure the amount if IR radiation that’s being emitted from the surface, which is directly proportional to the temperature. The emissivity of glass is really low though, and IR thermometers don’t have a variable emmisivity setting to correct for that.

You can get a more accurate reading by placing some strips of black insulation tape on the glass, giving it a while to equalise the temperature and measuring that. You have to get quite close though because the measurement area spreads out as you get further away. Generally there’s a diagram on the side of the thermometer or in the instructions that show this, the lazer, (if it has one) is just a pointer to show the middle of the measurement area, it has no measurement function.

its not a particularly expensive repair

How much is “not a particularly expensive”? Half of mine are blown, I just ignored it.

Expect to pay around £30 per unit for an in situ repair. They will take the beading off, drill the spacer and inject a drying compound which removes the residual moisture, then usually put new silica gel in to absorb anything that works it’s way in over time. Finally reseal and put the beading back on.

To replace the glazing units in full should be around £60 per unit so you may decide to simply do that depending on how many you have.

80 euro for 11 cubed meters of extra pure technical grade argon.

Refill 5 quid a windiwy, 10 quid for new seals and 45 quid for the rest.

60 quid each which is a long payback time.

Uh, if the unit has blown, won’t they have to remove the entire panel to replace the seals?

Or am I being dim?

I replaced several of the panels that had developed condensation inside last year.
A 3 x 2 ft panel was no more than £15 from the local glazier.

Double glazed units don’t last for ever, new units (and frames) have improved significantly in the last 20 years in terms of thermal performance. If you want a quick reliable repair I’d replace the sealed units rather than repair failed ones. The extra cost will be repaid with improved performance and long term peace of mind.

You might need to get humidity lower than 45% to avoid condensation. Is there condensation on other cold surfaces? Check thermal bridges, any poorly insulated walls, especially corners or behind furniture up against a wall, doors which are often less well insulated than windows.

If they are 20 years old they might be the old type that are really insecure, some you can pop the glass units out from outside the house. I thought I could replace the ones I had in the house I bought but an expert showed me why they were so bad (besides having lots of blown glass sections) and I ordered new windows sharpish!! Made a world of difference.

Double glazed units don’t last for ever, new units (and frames) have improved significantly in the last 20 years in terms of thermal performance.

Good ones will last decades though, all ours are still fine and coming up on 20 years old, parents house all OK after 30+ years; both from Anglian Windows.

60 quid each which is a long payback time.

Value of being able to look out of your windows instead of at a load of manky condensation… priceless.

I’ve got 3 blown units in my house. Hard to replace yourself? I’ve got a good supply of chunky mates and a suction cup carrying thing. One is fairly massive.

Assume you need to remove them to measure properly as some will be hidden behind the bead.

You don’t need to move to measure though I’m sure there is a correct method to get the right size.

60 quid each which is a long payback time.

We ignored the blown glazing units for 11 years. Apart from the lack of condensation on the window cill the main change was a feeling of agoraphobia when I suddenly realised we had a view. It’s not all about saving heat.

We get some condensation on brand new windows about 1cm max along the bottom.
I dont keep the heating on all night though so put it down to that, some rooms drop to around 14c overnight, plus you have us breathing moisture into the air.

One of out kitchen panel’s exploded this weekend. The window’s been in 10-15 years and I heard a bang when I was outside (usually the cats chasing each other and knocking stuff off). Didn’t think anything of it until we later noticed a huge crack on one inner pane. Got the local company coming out as there is a decorative bar inside the unit to give the look of two windows, and they will need to re-use it for a match.

How much does a failed unit actually affect its U-value? We have a couple of failed units that are on the list for replacement; but I can’t really say I’ve noticed any difference in how warm the window feels from others which are okay (I assume, anyway; I was surprised how long it took for the failed unit to actually look different permanently rather than just under fairly specific weather conditions).

We get some condensation on brand new windows about 1cm max along the bottom.

We get that in our bedroom, I put it down to several litres of moisture from our breath with no where to go. I just open the windows whilst we have breakfast and then close them before I go to work; to air the house.

DG units don’t fail or “blow”. From day one they begin to collect moisture so condensation is a certainty, it just depends on how long it takes. What happens is that the units have tiny breather holes in the separator to allow atmospheric pressure changes to equalise otherwise there would be an unacceptably high level of sudden breaks as Atlantic lows and North European highs came and went. Every time atmospheric pressure increases (like now) a few molecules of moisture find their way inside with the air and stay there, so slowly the humididty level increases until it overwhelms the dessicant beads and condensation forms.

If the breather holes can provide enough flow to keep up with atmospheric pressure changes, how do argon filled units stay argon filled for very long?

DG units don’t fail or “blow”. From day one they begin to collect moisture so condensation is a certainty, it just depends on how long it takes. What happens is that the units have tiny breather holes in the separator to allow atmospheric pressure changes to equalise otherwise there would be an unacceptably high level of sudden breaks as Atlantic lows and North European highs came and went. Every time atmospheric pressure increases (like now) a few molecules of moisture find their way inside with the air and stay there, so slowly the humididty level increases until it overwhelms the dessicant beads and condensation forms.

That’s just utter drivel!

They are sealed units. The tiny holes you can see allow the air sealed inside to access the desilicate in the aluminium frames, which dry out the air inside (which isn’t 100% moisture free when sealed).

If the edge seal fails over time, there is enough desilcate to keep the moisture at bay for some time, but eventually it will all get saturated and you’ll see condenstation.

Anybody ever tried a DIY repair?

Found this kit from condensation2clear.com – fixes 4 windows for £39.99
https://condensation2clear.com/

Essentially you drill two holes in the glass, drop in some disappearing drying pellets and insert plastic plugs in holes.

Looks like a bit of a bodge to me.

We are just replacing a failed unit on an old Velux skylight and it’s turning into a bit of an epic because the model number (GGL-6) has been superceded and you need a special seal kit for the unit, which also sounds like a bodge so since the woodwork is quite badly stained inside we’ve decided to replace the entire thing. More expense.

teef

Member

Anybody ever tried a DIY repair?

Found this kit from condensation2clear.com – fixes 4 windows for £39.99
https://condensation2clear.com/

Essentially you drill two holes in the glass, drop in some disappearing drying pellets and insert plastic plugs in holes.

LOL, good idea, but I don’t think that will work on mine, there’s about an inch of water sloshing about in the bottom!

I’ve seen that in a rail replacement bus, it was quite entertaining.