More to explore:
Owens Corning FOAMULAR R4 Tongue and Groove Insulating Sheathing 3/4 in. x 4 ft. x 8 ft.-37L at The Home Depot $17.45
Or for $16 I could get one sheet of this, and slice it the long way into one inch wide sections, and then glue one to each wall stud. I could do the all the wall and ceiling studs with two of these - so $32 for the whole house, and they're 1/2" thick, so would do a better job. Owens Corning FOAMULAR 1/2 in. x 4 ft. x 8 ft. R-3 Squared Edge Insulating Sheathing-36L at The Home Depot.