I have a Block building with insulated roof (40 x 52) 12' walls. I store my gooseneck trailer with some equipment, my dad stores his travel trailer in this building as well. Inside never gets below freezing in this building with no heat. My pole barn fifth wheel storage building (30 x 80 with 16' walls) has an insulated roof with translucent panels every 6'. This building is not insulated except where no skylites are installed. This building will get to the same temp as the outside, I can't remember that old block building feeling that much warmer when we ran our shop out of it though, seemed cold then. I would put the anti freeze in your camper to be safe either way.