Polycarbonate greenhouse panels are UV protected, but there's no way to know what kind of UV protection was used on your windows. You could 'test' them by using one in a makeshift cold frame to see how they do.

Hi terrybull,

6400'- are you in Colorado?

Mark

no, i live in idaho. a little valley surrouned by mountains(teton moumtains) 15 miles from wyoming. 80 miles south of west yellowstone.