Strange condensation pattern on new window

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We had sliding doors fitted a month ago and whenever it is frosty we get a circular condensation pattern right in the centre of one of the doors.
Our builder has told us we have a cold spot in the centre of the glass, and also the gap between the panes of glass is much smaller in the centre than at the edges which he said will be the cause of the cold spot.
Is any of this normal?
They’ve been installed in a new extension so it’s just been plastered/painted etc so I know there will be a lot of moisture, but my concern is the glass is colder in the centre and gap between panes is smaller....
thanks
 
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Oh I should add the condensation is on the surface into the room. So not between panes.
 
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We had sliding doors fitted a month ago and whenever it is frosty we get a circular condensation pattern right in the centre of one of the doors.
Our builder has told us we have a cold spot in the centre of the glass, and also the gap between the panes of glass is much smaller in the centre than at the edges which he said will be the cause of the cold spot.
Is any of this normal?
They’ve been installed in a new extension so it’s just been plastered/painted etc so I know there will be a lot of moisture, but my concern is the glass is colder in the centre and gap between panes is smaller....
thanks

Ive never seen condensation like that before.

Your builder is slightlycorrect - the gap is not likely to be smaller -Its true toughened glass isnt flat and that panes can go in a bit, but its not much, id be surprised if there much of a temperature gradient from edge to centre due to reduced air gap. There is hardly any difference in u value once dg units go above 22mm thick.

My guess is that you have anthracite grey aly frames and they have absorbed the heat and warmed the glass enough to prevent condensation apart from the middle.

You can easily check the flattness of the glass, just put a flat edge across it and see if you get a dip in the middle.

The glass surface will be colder on the inside than the ambient temperature, but it wont vary much across the pane.

You wont get condensation once the building dries out, I wouldnt worry about it.....its temporary.
 
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Ok thanks, we do have another pane of glass right next to it which doesn’t get any condensation on, just this one which is odd.
With the builder mentioning the gap he did a ‘test’. He put his finger on one side of the window, I put mine opposite his on the other side of the window. Nearer the frame the gap between our fingers was obvious, but when we moved them to the centre of the glass the gap seemed to disappear. It was if our fingers were touching. I think that’s why he was concerned the pane has bowed quite a bit.
I’ll see if I can put something flat along them to see if they do bow inwards.
Thanks for your response
 
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Big panes like this do tend to bow in, maybe Ronnie can confirm this but whenever I've seen large units being made like this before they were fully sealed you would stand the unit up in a rack or A frame and with a sucker on each side you would pull the middle of the glass apart so the unit in effect 'inhales', at the same time the last inch or so was finished off the hotmelt or polysulphide depending with system you were using, you woule keep the pressure applied on the suckers till the seal set. Maybe the glass is so close to touching your getting a cold bridge? I think your looking a a replacement unit though
 
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I go with crank on this one. My SIL works for a glazing company and he once told me all 'cells' are placed vertically after one edge has been sealed with the hotmelt to prevent 'dipping' on large cells.
A replacement cell is the order of the day. You don't need a new frame so and plaster work need not be damaged. It's simply a case of replacing a damaged/broken pane.
 
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Thanks for your replies, I was thinking as the glass panes are so close it’s getting much colder in the centre than the rest of the window causing condensation....
I just don’t know how to convince the fitter of it. He’s said big panes can bow in cold or hot temperatures, and it sounds normal......
 
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There is a fault and to be fair its not the builders fault, its whoever made the unit/s, it's the glass shop really. Maybe the unit can be taken back to them, they then cut back some of the hotmelt and then pull the glass apart while resealing, they could also fill it slightly with compressed air to push the glass apart
 
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Oh yes sorry I’ve spoken to the person who we bought it from and who fitted it, he said it sounds normal and all big panes will bow in hot/ cold weather.
it was actually our builder who said to me there shouldn’t be a cold spot in the centre of the window!
 
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At the end of the day you shouldn't have to live with a patch of condensation however it being caused, however as you've pointed out already the room has recently been plastered so while its drying there will be moisture in the air AND as a consequence of a cold spot forming in the centre of the unit the moisture laden air is condensating on the cold spot, maybe just maybe one the room has dried out it might not happen again, its a tough one but I would explain you shouldn't have to put up with it who's ever fault it is, not your problem
 
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Thank you, I’ll speak to them again
 
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There is a fault and to be fair its not the builders fault, its whoever made the unit/s, it's the glass shop really. Maybe the unit can be taken back to them, they then cut back some of the hotmelt and then pull the glass apart while resealing, they could also fill it slightly with compressed air to push the glass apart

I believe they expel the air from between the glass by having a small hole at the side of one of the top corners and another at the bottom diagonally opposite. Argon gas is then fed into the top one causing the 'normal' air to be expelled at the other hole. Once all the air is expelled the lower hole is sealed and then the pipe withdrawn from the top hole which is also sealed. As argon is an inert gas and heavier than air it prevents the transmission of heat better so maybe they didn't put enough argon in.
 
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I believe they expel the air from between the glass by having a small hole at the side of one of the top corners and another at the bottom diagonally opposite. Argon gas is then fed into the top one causing the 'normal' air to be expelled at the other hole. Once all the air is expelled the lower hole is sealed and then the pipe withdrawn from the top hole which is also sealed. As argon is an inert gas and heavier than air it prevents the transmission of heat better so maybe they didn't put enough argon in.

And what the industry doesn't tell you Conny is after about 3 years the argon will be all gone anyway, the seal is permeable and the gas leaks out
 
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Thanks for your replies, I was thinking as the glass panes are so close it’s getting much colder in the centre than the rest of the window causing condensation....
I just don’t know how to convince the fitter of it. He’s said big panes can bow in cold or hot temperatures, and it sounds normal......
Charles' (Gas) Law
 

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