Heat are our friend! The older we get the more important it seems.

I've got a 55k btu gas fired unit hanging from the ceiling, about 1500 sq.ft. of space. With overnight temps in the low 20s the shop gets down near 40, takes about 1 1/2 hr to bring it up to near 60. Depending on how much I expect to exert I find 55-60 comfy. Many moons ago used to use the torpedo (salamander) type, besides the fumes the noise was pretty annoying too.