Stop in for a cup of coffee
I built mine 32X42, and I used a heat pump system with LPG back up heat. I have one long Duct in the ceiling with 8 outlets. I like the system because, I turn it down to 50, in winter when I leave at night. When I come back in the morning, I turn it up to 65-68, then The LPG gas lights, and gets it up to temp, pretty quick. When it gets within 2 deg of my setting, the heat pump takes over and keeps the temp. I have AC also in that system, but it is rarely used. My building is partially in the ground and shaded by large trees. I just run the 4 ceiling fans in the summer, unless its over 100 outside..