Call me crazy, but someone (maybe Carol) posted a link to an experiment they did with the UVB lights and they said that a 10.0 through screen was putting out as much UV as a 5.0 without screen. And since most of us keep out lights on the outside of the cage, I don't know, I can see how it makes sense. Although you can get the same effect using foil to increase reflection, which is what I'm doing.