Revisiting insulation choices for my old house – GreenBuildingAdvisor

1700s timber-framed original structure with 1800s balloon-framed addition in CZ6.

Gut rehab begun in 2021. All interior walls and ceilings were gutted to the original framing.

I had chosen to economize from the outset. My approach was to cut and cobble (using 1” XPS in the walls, directly against the board sheathing, and 1/2” polyiso with a 1” airspace beneath the roof sheathing), and then fill the remainder of framing cavities with un-faced fiberglass batt insulation.

The ceilings were furred out to a depth of 7”, and the walls to 4”. Roughly R-25 in the ceilings and R-15 in the walls.

Air sealing efforts were exhaustive, and they have paid off from a strictly numbers and comfort standpoint. I knew the insulation level in the ceilings was insufficient, but I did what I could with what I had available.

I’m looking for feedback on the walls at this point. My concern is mainly based around potential condensation within the wall cavities.

I know my path forward for the ceilings is to tear off the roof shingles and sheathing, (fill the airspace above the existing polyiso with rigid foam) and add 4” of polyiso on top of the new sheathing. I know there are details I will want to flush out before I tackle the ceilings, but that project is still a ways off.