FWIW, I have all of my ball racks in my bedroom, which was an addition to my house. The room on a whole can drop down to as low as 68 degrees during the winter nights, but the temps inside my racks (using flexwatt and thermostats) stay at approx 84~86 degrees on the hot side of the bins, and down to approx 78 degrees on the cool side. I use no supplemental heat in the room. I have NEVER had a case of RI or any other health issue with any of my BP's maintaining temps like this. In fact, it's my belief that the lower ambient temps and decreased lighting that spurs such a strong breeding response with my BP's.