I've got a 26'X36' uninsulated gambrel garage (home workshop) which I currently have an oil fired hot air furnace installed with ductwork running down the centerline of the garage. This has worked well over the past 10 years or so but needs to be replaced (about 40 years old!). I'm looking for some guidance on the type of replacement I should purchase. I'm leaning toward propane (no natural gas in my area) and prefer to get away from oil as the barrel takes up space inside the garage and a external propane tank would be easier to get filled. I like my ductwork system it spreads the heat evenly throughout the space so I prefer to go with a floor furnace again tying into the same ductwork. My current venting flue needs to be totally replaced (exits through an upstairs window). I also shut the system down when I'm not using the shop so in the winter (Maine) it gets down to freezing inside the garage. I was looking at a high efficiency furnace for the ease of venting it but the water trap would be a pain to keep from freezing when not in use. An 80% efficient would need an entire vent system installed. I'm handy enough to do the installation but want to do it right. So any recomendations or suggestions?