I am in the process of forming up the slab for my new house. I live in southern Louisiana, so radiant floor heating isn't really needed. I do plan on having a contractor come out and install a Gshp, a 3t and a 2t waterfurnace. I have read some on radiant floor heating and cooling, but was curious if I could run the tubing in the concrete (post tension if it matters) and put a valve system to where in summer when the ac is working have the returning water go through the floor before going to the unit and in the winter have the heated water go through the floor before going to the wells. It seems like it would help the units cool or heat the house. I did have a igshpa accreditted company design the system and asked them, but they did not know.

Geo return water in the floor is a lot of trouble for no benefit. In the South, assuming a closed loop system, during summer, your loop field water temperatures will be above desired room temperature setpoint for much of the summer. It is possible that at the beginning of cooling season, it may provide some (minimal) benefit. During heating season, it would seem the water will be below room setpoint. The work to do such a thing is not justifiable.

Dew point is a big issue with radiant cooling and takes some sophisticated controls. mtrent is correct as well in a typical design the LWT would be higher than your design room temp.

You could make one unit WtoW and one WtoA and then have a combination of radiant cooling with air dehumidification and cooling. That's like a DOAS system and gets you somewhat higher efficiency and smaller ducts.