As you probably already know, you have plenty of options. You can try adding panels that can be removed when you want fresh air again. If you're willing to spend more, you can have it enclosed more permanently and get a longer season, in which case you might want to include sliders and windows to allow for a "breeze" when the weather is right. You might also want to include a ceiling fan. And don't forget, you will want to cover any gaps in the flooring. I had a porch enclosed last year, and I found that sliders, windows or french doors were worth the expense for the flexibility. Speaking of flexibility, I avoided the "sunroom companies" because I knew what I wanted and they offered very little real flexibility. If you told us more about your current porch and your priorities, also where you live, maybe we could be of more help.

I am looking at ReliaBilt windows at Lowes. They are made so the windows come out for cleaning - I will be taking them out and leaving them out for the summer. I will certainly be careful about buying windows with the correct heat gain coefficient and U factor. I am concerned if I do not completely take out the windows, I will still get too much solar gain in the summer from the south facing windows. As to water entering the room: The north wall is the original house wall so there will be no windows there. The east wall is beside a covered porch so no rain will enter there. The south wall could be problematic for sun and rain. I am hoping to minimize these problems by having a 2-ft roof overhang and then running an 18" awning type porch valance across the overhang. The west wall will also have a 2-ft overhang. These windows will have awnings to help protect the interior from sun and rain. I do plan to fully insulate the room and to use a direct-vent gas stove to warm it in the winter. I don't plan to cool the room at all. I will install 2 ceiling fans (the room will be 16 x16). I live in the mid-atlantic region. I looked at the Harvey Industries system, but they are not located near me. I plan on having a regular foundation. I appreciate all the comments.

There are companies that specialize in converting covered porches or screened-in porches into 3 season rooms. We just bought a house that was initially constructed with a covered porch on the back side of the house, and the prior owners used a company like this one (link below) to convert it into a 3 season room. I absolutely adore the 3 season room, it was one of the best features of the house. 2 sides of it are basically all glass, mine looks almost identical to the last before/after photo in the link below. I adore sitting out there. I have no idea if this company is any good - it's just the first link Google came up with for me as an example to share. https://www.patioenclosures.com/patio-and-porch-conversions-before-and-after.aspx

What kind of setup do you have? Do the screens stay year round and the storms are interior? That's kind of what it looks like. Depending on how snug the current storms are... you can use weather stripping around the edge to make the storm snug into frame. Screw small handles into the sides of the storm frame to make it easier to push and pull the storm in place. You might want two on each side, the windows look kinda big from the pic. Drill a few small holes into the sides and bottom of your sill- use wooden pegs to hold the storm in place during winter. You can also do this with barrel bolts and include the top of the frame, using the bolts on the window and holes in the sills. Or for a much more attractive look, use casement locks.