First, pictures:
Interior wall
Ceiling & rafters
Exterior wall
Under the carpet
My 1962-built house in Ohio has this three-season sunroom in back that was converted from a covered rear patio. For the first few years I lived here, I tried to use it as year-round office space, but it stays too humid back there during the spring/summer/fall to not have A/C or a dehumidifier going at all times, and I can't effectively heat it during the winter, so for the last couple years it has just been used as non-climate-controlled storage. I want to change that this year and make it habitable year-round.
From what I can tell so far, looks like the existing walls are solid enough, so I think maybe I could just add insulation and drywall? I don't think those ceiling rafters are functional, looks like they're just hanging there, so was thinking maybe I could remove them and raise the floor off that concrete patio slab some too.
All advice is appreciated - I'm not an expert on any of this, though I do have some experience performing the actual labor that would be required once I know what I need to do.
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.