All canvas popups are 3 season RV’s. 32* and less and the situation is problematic. When I had a FWC the bed was the biggest and most important problem issue. A good nights rest was what it’s all about. First was the bed comfort or lack of and then after a few nights it was cold damp mattress. Solved with Froli system, works for moisture under the mattress and adds comfort to a popup’s thin mattress.....http://www.frolisleepsystems.com/service.html I sold the FWC/Tundra moved on to a Tiger CX RV but kept the Froli springs which I still use. BTW, Some lite exhaust venting is the key to moisture build up in RV’s.