I suggest take a look at the ProVia Endure high grade vinyl window.
Triple pane is what I sell now and has very low U-factor and air infiltration.
I love their low profile slim casement window, just ... read more
Dan, Both Hardie Plank and a 3/4" and 1.5" insulating foam board are good options. There is also the choice of using Insulated Siding that is a custom contoured foam backer. It fits to the specificati ... read more