I would like to build a small (1000-1500 sq ft, but hopefully closer to 1000) two story home with radiant heating in the earthen ground floor, but on the second floor things seem to get much more complicated.  I was wanting to do something super simple like 2x6 tongue and groove with the joists exposed to below.  But if I want radiant heat in the second floor, I need multiple layers of wood or possibly even concrete, and then some insulation below.  This doesn't fit at all with the minimalistic approach I would like to take.  I am going to DIY as much as possible and I also feel that it's wasteful to use so much construction material (and concrete is such a huge CO2 emitter in its production).

So if I have an air source heat pump in conjunction with a hydronic ground floor, what are some decent options for heating the second floor?  Radiators?  Baseboard electric heaters (bleh)?

Or could I get away without any heat on the second floor since heat rises?  If I just made sure to circulate the air well between the floors...?  Especially since it will be a small place.

radiant doesn't heat that much air, and it doesn't heat it that hot, so the stratification affect is greatly lessened and not typically adequate for heating 2nd floors.

is the 2nd floor flat ceiling? could do a radiant ceiling. otherwise, you're probably looking at radiators.

The second story will have a low vault ceiling. (semi-loft, I guess you could call it)

Don't radiators run at a much higher temp than radiant flooring? Can I do both with the same heat pump?

that depends on your heat load, and the size of the radiators. depending on your water temps (hopefully very low) the radiators might get fairly large, but then, your heat load up there might be fairly low, especially if there is *some* heat migration from below.

so, definitely "maybe" ;)

Ok, so bigger radiators = better. Makes sense. The bigger a radiator becomes, the lower a temp it can use, and the more similar to a radiant floor it becomes. I was kind of digging the idea of an old-time radiator aesthetic, but I can get over it.