On ours tanks were not heated, the black and gray is all one tank, located in floor, centered and full length of the TC. Fresh water is under the step up into the bedroom. There is a duct from the heater into the basement that fed to all the basement and under the fresh tank. The only thing that froze was a line to the toilet and for some reason it was plumbed outside then into the bathroom, I built and insulated a box for it and never froze again. As for condensation, it is common for all RV's that are closed up tight to do that but with proper venting this can be cured. Ours does not have the double windows but when cold we use cut to fit "reflex" in the side windows to help some. Drop me a PM if you like and may be able to answer more? In case you did not know they were built in Caldwell Idaho.