Can you add exterior rigid foam insulation when replacing windows?
We are contemplating an energy retrofit to several 1960's chalet style cabins in Northern VT. Budget matters and the windows of the cabins are in reasonably decent shape. We have a strategy to insulate the attic space and crawl space but were wondering the most cost effective method to insulate the walls and if we can do so without replacing/resetting windows. The current walls are 2x4 with fiberglass insulation and plywood exterior. Is there a method to do this that would not put the structure at risk from water penetration? How much benefit would we get from just insulating attic area and crawl space? We were going to install cold weather heat pumps and realize that an efficient building envelop is important for these work well.