Currently my garage is 28' x 32' x 10'. I have R-13 in the walls. ceiling is trusses. I installed 3 1/2' in bottom of truss then put 9" the other way. This gives me a R-41 in the ceiling. Going to heat a additional area of 12' x 20' will use 3-1/2" in walls and thinking of using blue board for the roof. It has a sloped ceiling. with 2 x 8 rafters. Currently i have a modine heater that is hooked up to my outdoor pellet boiler. So my question is do i get a bigger modine heater or just purchase another one , and then have two of them running in my garage.This link to the modine i currently have:
http://www.shophmac.com/modine-hsb33.html
http://www.shophmac.com/modine-hsb33.html