I've been reading a lot of articles and questions/answers from this site and many others in preparation for a re-siding project. I am located in South-East New Brunswick, Canada, our climate zones run different than the US, but I believe it would be similar to Bangor ME which is zone 6A.

To the best of my knowledge the wall construction (1977 build) is, from the outside in, vinyl siding, felt paper wrap, board sheathing, 2x4 walls, fiberglass batt insulation, 6mil poly VB, 1/2" drywall.

Because of the low insulation value of the 2x4 wall construction, I would like to add exterior insulation while re-siding the house. In my research, there seems to be some concerns about creating a moisture problem when insulating the exterior of the house if there is an interior poly VB present. I am not planning on removing the drywall or poly VB. I read up on Roxul comfortboard IS, but based on feedback on this board there seems to be some issues with it in respect to compression when installing strapping causing a wavy siding install.

So what is the best approach for an exterior only renovation in this climate zone with a poly VB installed on the inside? Don't add exterior insulation, or add XPS, EPS or MW rigid insulation? Or some other product I am unaware of?

Thanks for any feedback.