The uth is not going to heat the air in the cage like you are wanting. Your best bet is to add another heat source on the warm side if you have a glass tank.

My living room is 68-70 so with a 40 gallon glass tank I have a uth, 100w che, and a 60w bulb on the cool side to keep the temps right. I also have my back and sides covered with thick paper which gave me a few degree rise. Using foam or some other insulator will help raise your temps.

Tell us more about your setup and we can try to suggest a more specific fix.