You gotta remember too, a UTH will only heat a spot on the floor, not the air. If you are looking to heat the air, you need to either use a CHE, RHP or raise the rooms ambient that the snake cage is in. A lot of people don't realize this and assume a UTH will work fine alone in a cold house.
Heat travels up from the UTH and therefore warms up the air , additionally the floor temp where the BP spend is time is what truly matter, I will even go further by saying that the animal body temp is what matter.