this may help I'm not sure its more of a question to your question than a answer. I have a glass tank with a screened in top also with a blanket covering about 3/4 of the top I have a heat mat and a red nocturnal heat bulb on a thermostat. with a large bowl of water on the cool side. my tank is a 40 gallon and my humidity stays at 59-62% all the time. am I just lucky or is there something that I'm doing right.....