with what I'm heating it with now > ....1196 sq feet (10" tall to boot) 8.5 x 12' door, 2- 36"man doors and a 6'5 x 6' toy door ... 2-3x4' windows and 2- 6x4 windows,.I have a toyo 73 heating it 87% eff ...I have burned 1.94 as a minimum and 2.12 is the max "gallon per day"............ thats I have put thru her to stay warm and cozy for the last 3 years ......I come out with" 21 btu's a sq foot" to heat this building from the 15st of sept to the 1st of may ......am I doing this right??