1.) It’s desirable to keep all the natural light, but seems somewhat unrealistic to me - currently, there are 3 4x3 and 4 6x3 single-pane sliding windows back there, leaking out all my heat in the winter. I don’t think I can afford to replace that kind of footage with double-pane, so I’m weighing the possibility of removing about half of the windows back there and just keeping one end of the room nice and sunny.

2.) My house has no central HVAC. There’s a through-wall unit back there now, which I replaced about 5 years ago. It’s sufficient to cool the majority of my entire house on its own, though it leaves something to be desired as a heater. Installing a complete central HVAC system is presently out of scope, so I’ll have to stick with the through-wall unit for now.