Brettski,
You are correct on the spray foam. We use a seperate 6 mil vapor barrier so we spray foam any irregularities caused by plumbing rough in or structural components. The tubing is 1/2". While I do not discourage folks from have tubing projects engineered, we have found that 99.5% of the time 1/2" pex on 12" o.c. and 6" o.c. on exterior perimeter walls in a properly insulated slab will meet normal heat load requirements in west central MO. When we do exterior snow melt, we use the same above rules and step up to 5/8" pex (3/4" works better but is hard to justify the expense).
I found a couple more pics:
Vapor barrier install before foam (blue pipes are geothermal header pipes stubbed up at future mechanical room):
2" foam insulation install on floor (1" @ perimeter where floor slab meets foundation wall):
Hope this helps.
Nick
