Looking for some help in choosing the right size garage heater. I have a pole barn that is 30x32 with 10 foot ceiling, I have enclosed a portion that is 20x32. The walls were studded and R13 faced batts covered by 7/16 OSB, the ceiling has a wooden floor to a loft and I installed R13 to the floor joists below that. There a 4 windows, an entry door and an 9x8 ft overhead door. I have a 115,000 BTU kerosene torpedo heater that I am now using but want to purchase a ceiling hung FA propane unit. I borrowed a friends 30,000 BTU ventless propane unit and ran that from a 30lb tank just to see what it would do, well it ate up the 6.5 gal of propane in short order and did not seem to add much heat to the space. In the calculator it recommends a 45,000 FA unit but I am not sure if that is big enough but I don't want to oversize as it will gobble up propane. I only heat this space for 5 hours a day and when it is 30 degrees outside it starts out at between 45 to 50 inside and I warm it up to 68 to 70. Thanks for listening and any help appreciated.