Passive solar house, radiant heat, and hydronic solar – GreenBuildingAdvisor

Wasn’t sure exactly where this fit sorry if I categorized it incorrectly. I am in the planning stages of a small well insulated home build. The house will basically be a modified A-frame, technically it will be an extra tall gambrel on 4 foot knee walls so that I can have counters and furniture up against walls that are 90 degrees. Footprint of 24×36′ Full ICF basement as well as the two long 4′ knee walls and the rear 24′ knee wall. Building will be south facing and the south gable wall will be primarily glass. The first floor deck I believe I am going to do with an ICF decking system so it will be poured concrete with a ton of thermal mass I believe around 14 yards of concrete or roughly 56,000lbs. There will be an open loft in the back with half wall front (south) half will be open cathedral ceiling. Open floor plan, I believe I will do a spiral staircase roughly centered that goes from basement to loft continuous.  Insulation will be r-49 Minimum in walls and (hot) roof.

Ok now that you have the gist of the build a couple questions.

Am I crazy to do radiant heat with 20′ high cathedral ceilings? I will have some ceiling fans of course to circulate heat down but will I be making heat at the floor and losing it to the ceiling or will this work out fine?

I would really like to add hydronic solar for the radiant but house is already going to be passive solar, so on days where the sun is shining in winter (I am in Vermont and there are less of those sunny days than we would like but its always cold) Anyway, on days the sun is out I really should not be heating the slab at all the house with all the glass should really heat well on its own. Could I way oversize a basement water storage tank to use as additional thermal battery? There will be a poured patio outside so that could become a dump zone if I needed to get rid of excess heat.

If this is a solid plan how would you size the solar array?

I have about 1000 more questions for this build but lets leave it here for now.