It is often an issue cool rooms increase the challenge a lot. The simple solution is to raise the room temps. That is not always practical. Insulation will go a long way a secondary heat source will also help. The height of the enclosure also makes a big difference tanks with open tops sometimes are hard to heat due to the height and open toped ventilation.
I keep my snakes in a cool room generally 68ºF but careful attention to heating patterns and using a grab bag of heat sources keeps the ambient air temps 79-85ºF cool 80 and hot 90. It can be done it just isn't easy.
Insulation first, second heat source second (cool side uth) then it gets really custom my side turned tank is in the coolest room I have. It is working quite well. here is what I did plus insulation in the winter and fluorescent light day and LED deep blue night also help the air temps in my set up. It worked for me I could work for you maybe. No direct answers here it is individual set ups.
http://ball-pythons.net/forums/showt...arium-Solution