Followup to the question How do you install Larsen Trusses on a home in Minneapolis?

Ken Traefald
Updated: June 24, 2021

Perhaps my wording should have been, wrap the poly around the sheathing, then nail on the Larsen Trusses. My house like most in built in the early 1900's, has interior plaster walls with oil paint, 2x4 studs, and is insulated with blown in cellulose. The exterior sheathing boards are1x's. I’ve done thermal scans of the walls. There doesn’t seem to be excessive settling of the cellulose. I’ve checked the attic in the winter and there was no excess moisture. When you say, strip the walls, install a plywood sheathing. Do you mean to strip off the sheathing boards? If so, is it instead possible to nail the plywood over the existing sheathing? At that point you could tape the plywood joints. Then one could seal the edges of the poly to the wall plates and install the Larsen Trusses / Cellulose insulation.

I’m still looking at the Rockwool Comfort Board 80 option too. Would it work to use  a self adhering WRB, on the sheathing and then insulate with 8" of Rockwool Board or is there too much potential of condensation in the Rockwool in a house like mine?

I found online pricing at Universe Corporation for the Delta Vent SA wrap, at $569  per 561 sq. ft rolls. Is that the typical price? Alternatives: Henry Blueskin VP-100 wrap is $239 per 400 sq. ft and has perm rating of 33; while Grace Vycor en V-S WRB  wrap is $300 per 480 sq. ft and has a perm rating of 15.

I can special order Rockwool Comfort Board in 2"thicknesses. If I go this route, I’m thinking of putting two sheets up, then the horizontal nailers, then two more sheets. If I opt to insulate the basement outside, would you rest the wall sheets on the top of the metal trim of the exterior basement sheets or leave a small gap? When working with the sheets, what size do you normally use, 48x96 or smaller? Is it practical for one person, to handle a full sized 2" sheet? My installation would be basically what you did in your video.



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