cover 1/2 of the cage with a blancket. use about a 150 wat bulb. or a heat emitter that is a little more than that. go out and buy a lamp with a dimmer switch on the cord. then you can buy a 250way emitter and just dim it as nessary. i have my savannaha in a cage about the same size. and i run a 150 basking bulb on during the day along with a 150wat heat emmiter that runs 24/7. and that just makes the temps perfect. about 130 on the hot spot 100 ambiant on the hot side and about 85 on the cool. no matter what you do there is going to be a lot of heat givin off by the cage. you might want to put it in one of those other rooms you have. and close the a/c vent in there. it takes a little trial and earror. what i would do is buy a few different bulbs and try them all and find the wattage that works best for you. then box the ones that dont work back up and get a refund. then buy an extra few bulbs.