The only way I was able to get my cool side (also ambient) temp to stay where I wanted it was to heat the room. I keep all my enclosures in a converted laundry room where is is easy to keep the ambient temp at about 82 with an oil filled heater on a johnson thermostat. This way I only have to worry about heating a hot spot in each enclosure with one thermostat for all of them. The rest of the room is the cool side. I know this may not work for a lot of folks, but just in case you have a open large closet or small room you could spare. Also, as I mentioned in another thread, I am a huge fan on the Herpstat (ND in particular).