Dan,

Thanks for the response.  My situation is as follows:

- 900 SF

- 4" slab

- 2" rigid or insultarp (have not decided)

- liquid propane and solar HW system (depends on bids)

- residential - this part of my new home w/ living, dining, kitchen, office.

- don't know heat loss, but this part of home will be 2x6 w/ icynene 

Thanks,

PW