Great gift, Susie! I also love screen porches. On the radiant heat--yes that would require serious construction/insulation. At that point, you might also be think of large Pella glass sliders as the walls, so you end up with half glass, half screen when they are open.
Alternatively, a good contractor should be able to figure out fully removable glass for colder months.
We had my first suggestion in Mass years ago, it was wonderful. We basically lived in the room. Today we have just screens, no heat or insulation. This is even more wonderful when it's warm enough, but obviously not as usable.
You can't go wrong with either--greatest gift ever
