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
There is no short, easy, or inexpensive answer here. In order to get a better handle on the situation and make appropriate suggestions, I would need to see more pictures.
There is not much right wi ... read more