Answers

It also depends on how high off the ground you are. Be aware that (at least in Wisconsin) if you are more than 24" above ground to the floor of the room, you can't use a vinyl product like PGT Eze-Breeze without a guardrail and balusters. But you can use a glass product such as the Mon-Ray Glass Walls porch enclosure windows, legally, without a guardrail. http://www.monray.com/gw.htm

Here's two examples of homes where we used the Mon-Ray Glasswalls.

There are a few options, depending on the use of the intended space. You can glass the space in to create a four season sunroom. This will insulate the room but can also be costly. There is another material you can use that is vinyl and looks and acts like real glass that is more cost effective. I have attached a video you can watch that demonstrates how this works. There are a few manufacturers that offer the same product. https://www.youtube.com/watch?v=oiGl8NFWSL0 

Good luck on your next remodel!

Bryan-

If you mean that the walls are 2 x 4 and framed already below the screens and you just want to replace the screens with windows, then you have a few options depending on your budget.

The most expensive we've done involved replacing the screens with Pella Designer Series casements and picture windows with miniblinds inside the glass.  A picture window with blinds can be made up to 59 inches wide, and a casement that will crank open has a maximum frame width of 35 inches.  That customer was very pleased with the result, and he had budgeted extra for the premium windows. Figure $1200 to $1500 per opening for that option.

The least expensive we've done involved Pella Impervia fiberglass sliding windows and we installed a couple of 6 foot wide 2-panel units and a couple of 9 foot wide 3-panel units.  They are strong, look like painted wood not vinyl, are energy-efficient and offer a lot of ventilation.  Unlike the casement windows that crank out and are somtimes problematic with backyards or walkways nearby, sliders can be opened with no projection.  Figure about half as much to do that.

Of course you can use single or double-hung windows but it would take 2 or 3 to fill the opening that a single slider can, and the slider will give you more visible glass and the same ventiliation.  The customer that used the sliders lived across from the beach, and he actually removes the venting panel from each of his sliders for the summer and puts it back in for the winter.  However he had a pretty wide overhang to keep out the summer rains.

As far as the A frame you can of course install triangular shaped windows to let light in and keep the cold out.  Consider something with a stronger Low-E coating in the glass to keep out the sun's heat. 

All of the above of course might require beefing up the framing below and between the windows to accept the extra weight over the screens.

Good luck with your project!

Joe

Yes, definitely check out a product from PGT Industries called Eze-Breeze. 

Check it out at http://pgtezebreeze.com/