Insulate the basement floor and walls well. Build the house as tight as you can. We used zip sheathing and lots and lots of caulk and air sealed everything within an inch of it's life. Southern Illinois is perfect for an air to air heat pump. When we built in 2020 we put loops in the slab for our house. Haven't hooked them up and don't think we will. This is MO north of I 70.