2nd house this morning, upvc double glazing, on about our 3rd window ( kitchen) when i heard a crack, front pane off the double glazing unit had a crack from top too bottom, cudnae believe it, checked water temp, set half way so not hot, checked air temp , it was 1*C , no probs on any other windows on same house, could only have been thermal shock i reckon, but didnt seem that cold , what can you do , phoned a local glazier and told him too fix it, told punter and she was really good about it, kinda made me worry for rest off day but we didnt have any issues, funny thing was we were cleaning last week in - temps with no problems , aw well