I had a number of Thermo World windows installed in 1999. The internal mechanism broke two years ago on two of them. The windows won't stay up so they have to kept shut at all times. I called for servicing, but was told to go to their shop, buy replacement parts and fix it myself. When I explained that was impossible they said they were too busy busy to do service calls (on their own product) and that I should get a private contractor to look after it. I'm having them replaced with Pella. They service their products and their warrantee is far superior.