CBearden
Your going in the right direction. I know from experience that it can be difficult to get good information. Alot have read about it. "It should work"
Yes indeed the heat will radiate to the second floor. Our first floor heated concrete slab warms the second floor no problem. BUT for air-conditioning you will need ducts in the second floor to allow the cold dense air to fall to the lower. If at all, you should need a little blast of heat to the second floor you can get a little blast up there with the air-conditioning ducts. But I doubt you will ever require heat to be forced up to the second floor by what we experience here. But for sure air con.
Insulation between the first & second floor totally not nessisary. Put that additional insulation in the second floor ceiling/roof. Min. code maybe R38 but R50-60 would really be the best investment. The greatest heat loss is through the roof.
If you have good sun fraction for your location the solar hot water can be a large portion of you heating load. But as mentioned earlier you require close to 30% of panel vs. floor area. And you can DIY. It will work.
This season for us so far for solar fraction has been very poor as we ve had no sun but in the past its been an amazing asset.
Yes you can hack your own heat-pump it will work and work well but:: numerous units with seperate HX or to add up to the total load for each zone could get expensive. Brazed plate heat-exchangers are not cheap. One unit sized correctly or just slightly smaller as AC Hacker had mentioned for your total load would be the ticket.
For our installation I was a control freak, each zone is on its own control. (temperature sense of slab) {1700 sq ft of slab}Un-nessisary with the exception of the attached garage. All the zones are set the same so one t-stat could have been fine. The slab heating is sooo uniform seperate controls are over kill. But since you have it better more control than not enough. The outside temp. sense is a good idea for the slow response for the slab but it will still take about 2 hrs for a 1 deg C change in slab temp.
We have had so many compliments on our heated floors from visitors we are very pleased.
My appologies guys, should have been in In-floor heating thread.
Randen