Hi,

I have been experiencing analysis paralysis for a while now on a wall for a house addition, currently, it is wood siding, 1.25 inches ventilation (double furring) then 1.25 inches of rockwool (R5), then 1.5 inch of woodfiber board (R4). My plan was to then fill the 2X6 cavity with cellulose and put 1 inch rigid foam insulation on the inside (also acting as the vapour barrier, and preventing condenstion on these odd days when AC is running). Unfortunately, I have issue with finding a way of putting the rigid foam inside given the usual bulge when cellulose gets injected, and all insulation contractor in my area insist on having a poly film installed before injecting the cellulose which makes it a problem with putting the foam afterward, unless I puncture the poly film. I have not yet have the cellulose injected.

I was therefore wondering, has there been any experience done with the flash and batt where the batts are on the outside and the spray foam on the inside within the 2X6 cavity. The cavity would therefore look like this: Sheeting, then 3.5 inches of rockwool batt, then 2 inches of sprayfoam which would go over the 2X6 in the inside to provide a continous air barrier. The strapping would be done with 2X3 on edge to give space to the spray foam to go over the 2X6. It feels like a more natural place for the spray foam where it can act as a vapour retarder and air barrier in the warm side, and can also properly glue the batt in place as it is sprayed after the batt is installed.

Thanks,

Jean-Francois