I do believe the Jayco HT line has vapor barriers, the flooring is tongue and groove 5/8", I believe" plywood and "bonded" walls as well as 5/8" roofing material and is walk on approved. They also have the "Arctic" package which includes full enclosure of the frame of the FW. Other than there being more space to heat, I have noticed no difference in ability to keep the FW warm on chilly nights between our Jayco HT 26.5 RLS and our 1993 Jayco Eagle 215SD with no slide and only abut 23' long. And that FW lasted us for 18 years without no breakdowns or even minimal problems.