We are building a home with SIP walls(R-26) and conventional trusses (R-50 cellulose). Most of our windows are south-facing (Low e, fiberglass), shaded by deciduous trees in summer. We are getting a geothermal heat pump, radiant heat in the basement, first floor, and 2nd floor bathrooms. We're getting some ductwork, mainly for AC and HRV air supply. Our feeling is that we will very rarely need to get heat to the upstairs with forced air. In our current, leaky, 1928 house, we have all the vents upstairs closed off because it gets so much hotter than the downstairs. Based on our experience here, we would like to have the supply vents for our new house located high in the wall on the 1st & 2nd floor (or in the ceiling), because our main concern is with getting the upstairs cool during the summer. Are we being foolish? Since our current house is forced air, it is hard to know if we will get the same heating effect upstairs with radiant.
We're in lower Michigan.