Triple glazed window - middle pane cracked???

Used to be 10 year guarantee but you’ll need to check with individual manufacturers, also check your home insurance policy as you might be covered under that.

I'm wracking my brain because I think I've heard of this happening anecdotally before and read some document similar to what BryanF has posted but I'm drawing a blank at present.

All the same - I'd suggest going to the window supplier first and would expect them to follow up with the manufacturer of the glazing unit. There are a very limited number of glazing manufacturers and they are all quite big and reputable - although I can't guarantee it I would expect you to have some success with them. There is no way a broken middle pane could be attributed to "wear and tear".

The only thing that concerns me is that this pretty rare occurrence has happened in your house. Is it the same window?

Spontaneous fracture is a rare enough occurrence but it tends to happen in batches. A contamination event occurs in the float glass line and a certain amount of glass - a day or so of continuous production - is produced before it’s picked up by Q/C procedures. The batch then goes out to glazing fabricators and that batch is likely to have a number of ‘episodes’ - such Nickel sulphide inclusions can manifest from anywhere between 6 months to 25 years from what I have been told. Relatively quick temperature changes common at this time of year – rising sun shining on cold glass - can set off the process. It’s not classed as a manufacturing defect by the industry. It’s more akin to getting a puncture in a car still under warranty. Apologies for not offering a more optimistic assessment.

You probably don't need to replace the frame. Just the glazing unit within the frame. Any local window supplier should be able to measure it up and order a new glazed unit to fit into the frame.

Did the window supplier cover the cost of the previous broken middle pane? fatty pang has a deep knowledge of the industry so if he says they don't usually cover the cost of the panes breaking due tho the contamination described he is almost certainly correct. I would personally be very p!ssed off if they walked away from what is clearly a defect caused during manufacture.

The local window supplier will not be making the units themselves. They will order them from the manufacturer. There is only 2-3 in the country.

And yes they can order them triple glazed, argon/krypton filled and coated, etc. etc. from the manufacturer.

The unit will very likely come from the same manufacturer as the original units though!