Hello, I have a long skinny 700sq ft bungalow home from 1920 built with 2"x3" wood walls (true 2x3s, no planed smaller) with no wall insulation. I have about r25 in the attic, and r7 ish insulation half up my finished basement walls (on the top half). Walls have no vapour barrier, and walls have lath, no plywood. They are balloon framed and the cavity is slightly accessible from above. Im having my siding removed and am wondering how best to upgrade our insulation. Spray vs exterior foam? R20 is what our building code requires, but I'll take what I can reasonably get.

Going back to my insulation days. Blownin cellulose would work and not cost a fortune. If your removing the siding simply drill and fill thru the exterior sheathing. You could also fill down from the balloon framing. Use a piece of 1 inch clear hose on the end of the reducer nozzle.