I have a 36 x 32 x 12 shop with 2inches of insulation under the slab and 12 inches blown in the ceiling and r24 in the walls, tin on the walls & ceiling , two walk in doors & a 16 x 10 insulated garage door. I have pex in the slab & using a 80 gallon electric hot water heater to haet it right now but it doesnt recover quick enough! I was thinking of going to a propane boiler but dont have a clue how to size one. Any help would be greatly appreciated. Thanks Northern Indiana 

You need to have an accurate Heat Loss calculation performed. We have a one on our website.

Good Luck!

Panelcrafter, I looked at your calculator and have some questions.

If using ICFs do I use the "concrete" row and change the R value to that of my ICF?

For SIPs what row do I use?

If I'm figuring 2x4 walls do I put in the R value of the fiberglass batts that I'm using (say R11) and does it adjust for the conductance of the lumber and use an effective R value of say R9?

If I use foam boards over the 2x4 with fiberglass batts how do I enter that?

Thanks!

Use either 2x4 or 2x6 and change the R-Value.
Again, use 2x4, 2x6 or 'Concrete Air', and change the R-Value. Do not use 'Concrete Earth' as the Delta T is based on the Earth temp.
You need to figure your whole wall R-Value. You can calculate that as a ratio between the insulation and studs, or however you choose. The software uses the R-Value that you give it. So, R-9 doesn't sound that far off. Foam board: Again you need to decide on an R-Value to use, and use it for that category of wall.

Good Luck!

Thanks PC, that will get me on track.