Youre off to a good start already.

I have one 20 gal tank that I heat with that exact UTH, the zoo med 30-40 gal. It is placed on the right hand side (whichever side you want). The UTH is controlled by a Herpstat thermostat which regulates it to between 90-92 F at all times. I use an infrared bulb w/ dimmer to control the cool side / ambient air temps. The temps I achieve are 77-80 on cool side, and 81-83 on warm side (ambient air temps).

To answer your question, if your house is naturally cold in the winter, you may need to purchase a heat lamp with a dimmer, and plug in an infrared bulb in. This will help regulate the air temps, as well as the cool side temps.