i use a hard ware mesh made of metal on top, pet screen and 1/2in plasticmesh on side. the petscreen blocked about 23% of uvb, 1/4 metal mesh about 13%, and 1/2in plastic mesh about 10%. that was compared to direct exposure. i used a light meter i borrowed from my sister, she is a photographer. the uvb light was a reptiglow Iguana, not shure what the uvb rating is on it. 7.0 i think might be 10.0?