Back heat works well with a tstat. The rack is enclosed and the heat radiates well and temps stay consistent.
The rat room is a 12x60 mobile home. We keep all the windows and doors open with big floor fans moving air. One big fan pulls air in the back door and another pulls air out of the actual rat room. Also have fans blowing on the racks. During the winter door fans stay and oil heaters are sitting next to the racks.