I just went through the same experience as Nancy F the other week. The CertainTeed Window installed by Northwest Windows & Doors last year in 2005 cracked during the cold weather the week after Thanksgiving in Seattle. Nothing struck the window from either side, but just simply cracked from top right corner diagonally to the bottom left corner... I also believed I had lifetime warranty, but not for cracked window and my warranty doesn't cover it...same excuses given to Nancy F. CertianTeed didn't even bother taking a look or even ask any questions from my claim, but simply took no responsibility and told me get fixed from another outfit on my answering machine... What's up with this warranty and with CertainTeed Windows!?