i dont even run a topical heat source as i do not need it in my house for ambient temperature. i have the sides and back insulated with 1/8th" packing foam and the glass is lined back and sides with black poster board. i have all of my screen top masked off with tinfoil except for 2" above the cool side. My cage has a ventilation grid along the bottom front under the slider doors too. i have a dimmer i made regulating my Hot side UTH to 94*F which gives me a gradent of 94 by the glass on the hot side, 90 in mid hot side with the hide over it. 85 mid tank down to 75 closest to the glass on the cold side. ambiant air temperature is 80*F the cool side hide is a home made one he seems to enjoy over the 77-80*F area.
i my self use a IR temperature gun to monitor surface temperature and a wireless national geographic digital thermometer to manage the ambient readings of in cage and external (room) temperature
it is important to regulate the CHE and UTH with a dimmer/Rheostat or thermostat