DIY Doctor UK DIY Forums

I say no reason but what I mean is they just cracked on their own-inside and out soem weeks after new installation,this seems to maybe have something to do with temperature differences?
Has anyone else heard of this?
They did not all crack but several did in different parts.
The cracks were jagged and single strand not spiders web pattern and remained sealed but looked unsightly as if someone had hit them with a hammer.
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Jainism Advice

the answer is simple.

all sealed units react to temperature. In cold weather the units contract and can even implode. in hot weather the units expand and can even explode.
problem can now be solved fit a defogger valve.

are these units on fixed part or on an opener possible cause twisted frame