Exploding Velux window - does this often happen?

[Nigel Watts]

At 4.15 this afternoon my wife and I both heard a smashing sound. She assumed I must have broken something, and vice versa.

The cause, it soon became clear, was the Velux window in ceiling of our downstairs loo which is located just above the sink. The inner sheet of glass had spontaneously exploded showering shards of glass onto the sink and floor. The outside sheet of glass is still intact and there is no apparent external cause. The window, in a lean-to roof, is of the opening kind and still opens freely and there are no signs of movement in the roof structure to have caused stress.

Luckily noone was in the loo at the time. If someone had been a very serious accident could have been caused. The window dates from about 2001. I intend calling Velux, the manufacturer, on Monday.

 

[philpjuk100]

That is alarming,we have one over a bed! ( it does have a built in sliding blind which may offer some protection )

 

[worms]

How strange!

Presumably it was a sealed DG unit? Was there a big temperature difference inside to outside, or srong sun on the glass for the first time since winter? Someone holding a long note on the cello? Earthquake? Poltergeists?

 

[Nigel Watts]

It was double glazed and the sun could have been hitting it, but that is surely no excuse for such a failure.

 

[Moo]

That's really alarming!
We've had two of the blighters in our kitchen for nearly twelve years, and no incidcents so far (touch wood).
I doubt whether it could have been the heat of the sun (especially at this time of year) because ours get the full blast on hot summer days and, as I've said, don't seem to be affected.

Please keep us informed, Nigel, about your progress with the manufacturers.

 

[Flyfisher]

Is it an opening window Nigel? If so, does it still open easily? My immediate thought is that something is 'crushing' the frame, stressing to glass to breaking point. Didn't you have some subsidence problems at one time?

Alternatively, have you spoken to the kids about it? :roll:

 

[Moo]

Those are very plausible theories, Mr F. Shows that the rest of us haven't been paying enough attention to earlier threads.

 

[JoceAndChris]

How freakish! Thank goodness you are OK and no-one in the family was hurt.

 

[Penners]

Flyfisher makes some very salient observations. But you may want to discuss the event with Mr Velux. I'm sure the company will be keen to ensure that their product is not at fault.

 

[Moo]

If Mr Velux has any sense he'll come round in person and do some Olympic-quality grovelling.

 

[BMcD]

I seem to remember a television programme some years ago concerning the spontaious shattering of toughened glass in shopping centres and swimmimg pool roofs. Unfortunately I don't recall much more than that, other than the cause was due to a manufacturing fault. However. here's some links which may be of interest

http://www.picams.com.au/documents/Toughened glass - with an achilles heel.pdf

http://www.expertexpert.com/tough.htm

http://www.velux.co.uk/en-GB/Documents/Brochure pdfs/UK Guarantee info Feb 08.pdf

 

[jocelyn plummer]

Nigel, I am glad you were all clear of the room at the time-- a very unpleasant thing to happen. My immediate thought was to wonder whether there had been an impact of some sort, rather like when a stone hits the windscreen, sometimes theres just get a mere dent and sometimes if the pressure point is hit, the whole screen goes. Goodness knows.

I am glad I don't work for velux :shock:

 

[Michelle73]

I have a Velux directly above my toilet (this replacing the old cracked pane of glass which had been repaired with a piece of masking tape and some cobwebs) was just starting to feel safe again.... :shock:

 

[Pford75]

Bird strike??? Do you have any low flying emu in London?

Seriously, glad you are all ok.

 

[Nigel Watts]

Spoke to Velux this morning. They handled themselves very well I have to say. They immediately recognised the issue and are sending someone round to replace both my windows next week, free of charge, no questions asked.

It seems the problem has to do with Argon gas leaking out of the gap between the two panes but not being replaced by air, causing a reduction of pressure and subsequent imploding. According to Velux this problem has affected about 1% of their two smallest sizes of window manufactured during some period in the past (didnt ask for details of this). The outer pane in these windows is toughened, but the inner one was simple float glass.

The replacement windows, they assure me, have modified seals to allow pressure equalisation and have a laminated glass inner pane which, in the event of failure, would not fragment.

 

[Flyfisher]

Well, full marks to Velux for customer service.

But I don't really understand their explanation. How can a leaking seal result in reduced pressure between the two panes of glass? I can understand how a leaking seal would result in the original argon gas being lost but surely it would be replaced by atmospheric gases, through the same leaking seal, to equalise the pressure? Or could the seal possibly only leak in one direction, acting as a sort of valve.

Good idea to have laminated glass in both panes though.

 

[Penners]

the problem has to do with Argon gas leaking out of the gap between the two panes but not being replaced by air, causing a reduction of pressure and subsequent imploding.

Well, full marks to Velux for their response. No quibbling or hand-washing. That's good to see.

But I'm not sure I follow their explanation. It seems to be against the laws of physics for the argon to leak out and to leave a vacuum behind it. Surely any seal failure between the two membranes will simply lead to the "gas- gap" between them resolving to normal atmospheric pressure.

Edit: Oh b*gger! There I go again, repeating what someone else has said, because I didn't spot the new page! Sorry, FF.

 

[Nigel Watts]

I believe there there is a phenomenon called "thermo-osmosis" which works with gasses in an analogous way to osmosis in a liquid system. Two different gases separated by a semi-permeable membrane, when subjected to a temperature difference, can give rise to a pressure difference building up between the two which does not reverse when the temperatures equalise. The temperature gradient causes a pressure difference (Boyle's Law) and pushes some molecules across the membrane. When the temperature then equalises, a pressure difference builds up in the other direction, but the membrane does not allow molecules back to counteract this.

 

[AMc]

Glad this is being sorted - when I was specifying the glazing for our vinery I was under the impression that both plates must be toughened in a roof. That's definitely what was delivered as we broke one and it shattered like a car windscreen into a million itty bitty pieces.

I can see that toughened upper and laminate lower has some benefits, the laminated holding the fragments of the toughened. I guess it also has security benefits. Too late for me to worry now

I'd have thought that if thermo-osmosis was the problem then all these sealed units would eventually implode?

 

[Penners]

I believe there there is a phenomenon called "thermo-osmosis" which works with gasses in an analogous way to osmosis in a liquid system. Two different gases separated by a semi-permeable membrane, when subjected to a temperature difference, can give rise to a pressure difference building up between the two which does not reverse when the temperatures equalise. The temperature gradient causes a pressure difference (Boyle's Law) and pushes some molecules across the membrane. When the temperature then equalises, a pressure difference builds up in the other direction, but the membrane does not allow molecules back to counteract this.

I knew that.





Ahem...