That's my whole point of asking about a propane heater that doesn't put the moisture into the shelter . I do have a Thermal insulated shelter . Don't get me wrong , my Buddy heater does a fine job heating it . But , I'm trying to figure out a way to keep the moisture out so you don't have 20 more pounds of weight and drying time after each day on the lake . The members on here are very inventive . Since most of us already have some type of propane heater , a hopefully simple & inexpensive heat exchanger would solve the moisture problem of a propane heater . But , so far all we have come up with is a expensive store bought option . The insulated duct work pipe and fan are simple . It's the heat exchanger itself that is the puzzle that needs solving . If I saw a commercially available one , I might be able to figure out a homemade alternative . Kinda like reverse engineering if you would .