You can use glass and still keep all the temps and humidity right. First u want to lay tin foil on the top of the screen lid, then I would suggest using Cyprus mulch as it Increases ur humidity a lot, and then invest in a shallow plastic ware dish of decent size and put half of it over/under ur heating source.
---
I am here: http://maps.google.com/maps?ll=36.863094,-76.206280
1.0 normal bp- Blitz
1.0 Nicaraguan boa- Gavin
0.1 Red Tail Boa- Tara