Sounds like you'll be letting your room drop down in the low 60's or so? I don't know what temps have to be to induce your ferrets winter coats, but sounds like it would have to be cold to do that. I like to keep my room temps around no less than 70-75 degrees (use an oil heater to maintain the temps). I can then maintain proper temps in the Tubs without issue. I would say you may want to just keep your BP in another (warmer) room.