How do I calc the BTU needed

rfcomm2k

New home construction in Willow, AK. Radiant floor heat in slab. First floor is 1400 SF with 625 SF open from floor to roof. Loft area is a 141 SF open office overlooking the open area below. 700 SF workshop also included. All exterior walls are 2x6 construction with spray foam insulation.

If you have other questions please ask.

NY_Rob

Give the Slant/Fin app a try, it's somewhat conservative so you won't go cold if you size based on it's findings (and use common sense).

http://www.slantfin.com/slantfin-heat-loss-calculator/