Let's get specific. When we say "cold in the house" we mean below 55 F. Not too likely if humans are living there too. Just to add info, chams do seem to see most colors, so if you use any type of light emitting heat source at night you will disturb them. Also, John, I would suggest we be careful about suggesting a specific wattage of basking bulb. The wattage will vary so much for each cage situation that you could unintentionally give someone the wrong idea. The safest way is to measure the temp right in the basking area. The wattage light that gets you to the right temp is what they will need. The wattage of the light isn't the important thing.