I have used heavy garbage bags to block off a majority of my glass tanks along with a lamp on them with pretty ggod success. The material holds up pretty well to the heat if it gets too close to the heat, and it does help hold the humidity in. Just cut it to fit on your screen top, inside the edging, and run some good clear tape down it to hold it in place. I put mine over the towel as well to help insulate and hold in heat as well, and you can still spray the towel as well as whats in the tank. Keep up your efforts, its worth it for healthy animals!