You can cover 2/3 of the screen top with tin foil or saran wrap, IMO the foil works way better. It will also help a lot to keep the heat in. Or you can buy a fogger and hook it up to a hydrotherm and control the humidity that way, but either way if you don't already have the top covered it will help both ways. You don't have the top covered the fog will dissipate pretty quickly. Hope I said that right.