There is no heat provisions in the rear compartment. In addition to cold air being uncomfortable, you can also get condensation between the mattress and the wood, resulting in mold growth. In these conditions I run a 200 watt electric heater in the trunk. I have a permanently installed extension cord running from the bedside wardrobe down to the trunk for this purpose.
"If the women don't find you handsome, they should at least find you handy." - Red Green