I have found a suppliers for some recycled (milk jug) plastic, barn sash type, single pane windows that resemble the windows I used in the prototype. They are a solid product and don't require painting. The prototype has www.Brosco.com wooden sashes. I have designed a screen setup for these but they are single pane. They simply hinge at the top, swing open and are latched open with a simple gate latch. The screens can hinge on the inside to allow access to the sashes and latches. These windows and the recycled ones I mentioned are inexpensive but don't provide the performance of the true Cadillac. www.Marvin.com With the SIP wall panel system I am able to install any type of standard 4-9/16" jamb size window. Another option would be windows like the Brosco barn sashes that could be clear pine or cedar.