Insulating an old home that has sheathing – GreenBuildingAdvisor

Good afternoon,

I am currently renovating my foyer and living room on my 100 year old house located in zone 4A.  The house is balloon framed with planked sheathing, some kind of tar paper, clapboard siding, some kind of foil paper and then aluminum siding.  The foil paper pretty much disintegrates if you touch it.  I have no updated WRB and don’t plan on re-siding the house.  The previous owner had the wall cavities filled with injection spray foam which I don’t think allows the house to breath/ dry properly.

My plan is to follow this detail for insulating and air sealing the walls. https://www.greenbuildingadvisor.com/article/insulating-walls-in-an-old-house-with-no-sheathing

Whenever i see this detail for insulation it’s for houses with no sheathing, mine has sheathing.  So my question is if I do this with 3/4 or 1 inch rigid XPS foam with rockwool on top, am I creating any problems because of the tar paper/ crappy foil paper on the exterior already?

Zone 4A doesn’t require a vapor barrier and if I’m correct up to 1 inch of XPS is vapor semi permeable so some moisture should pass through so i think it should be fine?  Any help or guidance would be greatly appreciated. 

Thank you,

Kevin