If I want to up humidity, I use heavy duty foil and tape it over the screen with holes cut out where the lights go. The rest of the enclosure is covered with a clear shower curtain over the top.If you buy the housing for shop lights you can hang the tube lights. A screen will not keep the humidity in.
I know, not the prettiest but it works. I have a separate reptile room so I'm not worried about how it looks.