Hmm, do you have a heater or fireplaces anywhere in your house currently? The heat pad will keep the cage a bit warmer but it will also dry it out and you have to be careful that it doesn't overheat the enclosure. Also, you are not supposed to just use heat pads that are unregulated by a thermostat. Those heatpads can get so hot that they begin to melt. Damp rags can help for sure but you are restricting ventilation as well, just not as much as the plastic.

Could you toss up some pictures of the room and enclosure?

Just always keep in mind that ventilation and heat are the enemies of humidity in a cage.

By the way, you may want to read over this caresheet I made, some of the information you have isn't the best advice out there.

http://www.thelizardhorde.com/caresh...tedgeckos.html