Just my personal opinion but why not use a under tank heater? The smallest one doesn't create a lot of heat. If you offer a cold and warm hide your snake will be able to do its own thermoregulating. Then the temp in the house will not be that important.
I use under tank heating on all my enclosure. I use Zoo Med under tank heaters on all my aquariums and Flexwatt on all my large enclosures.
Just an idea.