We are building an ICF home with 14 large arched windows. These windows will not open. I would like to to buy high quality glazing and build them in to the opening. From what I have read,  frames are the week link in themal conductance. With the structure being ICF, the exterior will be foam with polymer type stucco. I would like to wrap the window jamb area with a high density foam. This jamb frame would have a seat for the glazing. Another HD foam pc cut as trim stop, would be sealed to hold the glass in. Of cource the system would have to allow for glass replacement. Some HD foam can be as nearly as dence as wood. I'm targeting for a material that has structure but also high R-value.

The walls of an ICF are very thick, about 17" after we add additional foam. I don't like to look of wood trim and jambs on thick walls so plan to wrap the drywall around the inside wall to the jamb. This look is very common in Europe. The windows are typically mounted in the center of the wall.

Attached is photo that simulates the wall

What is the R-value of a good quality window frame? We are in Southern Indiana.

Patrick T