My garage is 28x24x12' ceilings... I need one big enough to take the COLD out, not just a southern chill...it's gets below Zero in NH. Buddy of mine has a 100k BTU in his garage and it's only got 8 ft ceilings..says I should go 125k min. I am going to go w/a Forced Hot Air Furnace, and I have propane here...so, can anyone talk from experience??