Re: Wrong Size Wall Studs on Exterior Wall
Install a layer of sheet plastic over the existing studs and block wall as a vapor barrier. It should be against the blocks without an airspace; you might need to use some spray adhesive to get it to stay there for the next step.
Then install 1-1/2" thick rigid foam board insulation cut to fit between the existing studs. So far, this is about R-5.75.
Install additional studs flat, but offset from the existing studs. This will provide thermal isolation so heat doesn't transfer from the wallboard to the stud to the next stud to the block wall. Insulate similarly between these studs. This will give you another R-5.75, for about R-11.5 insulation value.
If you want more insulation value, you can make the inner studs thicker either by building them up (adding 1/2" will allow you to use 2" foam board, with about R-10 value) or turning them "on edge" for an additional 3-1/2" which will net you an additional R-13 (with fiberglass batt insulation) for a total of almost R-19.
Even though the "R-value" might not be quite as much as a traditional 2x6 stud wall, the effective insulation value may actually be higher due to the thermal isolation of the staggered studs.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.