I think it's a DIY. You could replace the lower screened portions with windows, with interchangable screen panels. They'd have to be probably ordered in your custom dimensions though. Another option which would be less expensive - you could find glass or polycarb panels that can be framed, then clipped into the openings. That might not be as insulated as a decent window though, but that depends on your choices. Lowes sells Tuftex SeaCoaster panels, a wavy style in clear or opaque colors, in the roofing section, which can be cut to size with a utility knife or snips. An 8 ft x 26" panel cost about $20 last I checked. You could frame it and clip it in somehow to your sections, and then exchange it for framed screened panels in the summer. By the way, I like your wrought iron. I'm looking for something similar to put in 3 windows. Do you remember where you found yours?

Jeff, if you post a pic it will help generate suggestions. We had a three season room built and did sheetrock on the walls and a plaster cathedral ceiling.

Well, after looking into it a bit I agree that it would be good to insulate the area. But which is preferable, foam panels or fiberglass? If fiberglass is recommended, should it be placed between the roof joists or the ceiling joists? And how thick? If foam panels are recommended, they come in a multitude of thicknesses and types. What's recommended? I've searched for this online and didn't see much about insulating seasonal rooms.

Thanks for the smart points about rain, klem. And I agree -- there are just so many options, and people are so opinionated about those options, that it's hard to know what to do. My biggest concern remains the weather and how that will affect things, but I know that's a local issue. Maybe I should walk around the neighborhood and survey some people with porches about the sun and the temp, etc. Without adding any new information, my wife and I are divided on what to do -- she thinks just screening it is fine, but I think it would be really nice to have glass for the late fall / winter. If we had to decide today, I think we would either do simple / cheap modern storm windows (which could be opened to the screen on the bottom half during the summer) or do something a bit more adventurous. What I'm thinking on the adventurous front is to screen it in, but do it in a way where there's space to add the old-style wooden storm windows later -- just simple single-pane units that slide into the windo frames and attach with this: http://www.houseofantiquehardware.com/screen-hooks-storm-sash-window-hanger?sc=12&category=91 . The main thing would be attaching the screen on the inside of the frames, or at least creating an outside sill deep enough for the storm windows to nestle within it and still be flush on the outside. Then we could remove the storm windows and store them in the garage during the summer (though that wouldn't help with rainstorms you mention). Does that make any sense? If we did that, we could see how we like the screen in the spring and summer, but add the glass later in an affordable and removable fashion. I haven't seen many people try this, but I think we could build the storm frames and get the glass cut by a local shop. Basically we would recreate something like this company's product: http://chicagogreenwindows.com/storm-window-primer/