We have a Winnebago Aspect 26A Motorhome.
The Black and Gray water tanks are enclosed with a duct from the furnace that feeds that area. It also has tank heater pads on each of the tanks. We also put RV antifreeze in those tanks.
The fresh water tank is under the corner bed.
My biggest concern is the fresh water lines on the outside walls. Real 4 season units have the fresh water lines more inside. That said, when camping in cold weather we leave drawers and cabinets open a crack allowing warm air easier access to the pipes.
At this time we have never had a water line freeze. Our coldest camp-out was 25F when in Alaska.
