Do What? There? Continued

Hoist

I'm the nut that designed and will be living with the super high-effiency, radiant mechanical plant for space heating, snow melting, and DHW, that was referenced here a few days ago. Frank, Richie and the boys at Ranshaw Heating and Bob from Centa Plumbing are doing a tremendous job, especially considering the space constraints. With assistance from Rick @ Ranshaw, Mario at Centa, Don Rathe @ Rathe Associates and Pete Caruso @ Monitor, I've gotten the plant design and Tekmar control system down (sweet control system with all Tekmar controls integrated into a prewired control panel to my specifications, since the system is so complex). I'll try to get some pictures of the plant soon, since you guys seemed pretty into it.
I'd appreciate some real world responses regarding the back and forth issue of underslab insulation/vapor barrier. My concern is more with underslab water than it is thermal. Concrete is pourous and will have expansion joints. My 60ft. driveway is bordered by my and my neighbor's house. I'll be snow melting 1600sf with up to 200 btu/sf. Where is all the rain and melted snow going underground? With a sealed underslab and surrounding building foundations (maybe thru them?), won't I be trapping water under my new slab?
I'm new to this site so I haven't read any previous debates on this. My feeling is that I should only insulate/vapor barrier at the edges and prepare the underslab for draining rather than sealing. Heat rises and transfers from a higher temp to a lower. How much will these R-1 or R-3 "insultarps' really matter at the expense of underslab water damage?
Some real-world thoughts would be appreciated as concrete work will be done this summer. I still have time to design and/or redesign the snow melting portion properly. I'm real comfortable with the system design but am new to snow melting.
I enjoyed the enthusiastic responses I've read to Frank's "paintbrush 3D layout". I'm really excited about being able to do a project like this in my own home and I'm having a blast working with these guys. They're all fantastic craftsman and great guys. Let's hope all works well in the end. And no more shovelling!!!

Hoist

Radiant Baseboard

While I'm at it , I thought I'd ask if anyone has used the Embassy Radiant Baseboard Panels. That's what I'm planning to use for the 8 radiant baseboard zones (2row finned model) with 150deg max primary loop temp and reset by the Tekmar controls. Also, the 3 radiant floor zones (in tile floors) will use Telestat zone valves. Should I bother insulating the floor. The space below is completely conditioned? Any thoughts on these items? Thanks.