Should I densepack wall cavities prior to exterior insulation?

Gordon McNair April 13, 2021Updated: April 14, 2021

House was built in '64. We live in climate zone 5A, though on the edge of 4A (might be 4a in a few years). We opened up one wall during a kitchen reno and found R13 fiberglass. But it's starting to seperate from the kraft paper, and the paper itself is starting to fall apart. We would like to replace all the windows and siding, so figured an external layer of insulation would be a worthy investment. The plan for now is strip back to sheathing, new self adhesive WRB, new windows installed at shearwall, 2-3in eps/roxul based on price, strapping, new siding.

Is it worth densepacking the walls before doing the WRB?

Responses (3)

Gordon McNair
Gordon McNair 1 year ago

Mike, Thanks for sharing your wealth of knowlege. I really like the look of the ThermalWall but unfortunately can't accomidate anything that thick. We are limited to 4in of total wall thickness. That puts us in the 2in range for insulation.

My wife also prefers the "outie" windows which as you know presents it's own set of challenges. In trying to solve that problem, I found a company making a thing called Thermalbuck. They also have an insulation that works with the Thermalbuck to make a nice system. The insulation is Neopor GPS by BASF, which I can tell is an EPS foam. It seems to offer a slightly better R-value per inch than normal EPS. Have you heard of the Thermalbuck and Thermaltite products? Any thoughts?

Mike Reynolds 1 year ago

Hi Gordon, thanks for the kind words.

We don't dispute the higher R value claims of EPS foam with Graphite, that legit. As for other products - there are lots of new innovations in building materials, and we are very much in favor of any that help break thermal bridging, which these seem to do. Neither of those ones seem like snake oil to us!