2X4" wall cavity insulation

[weatherguy]

When my home was built in the Sierra Nevada foothills 38 years ago they put in R-7 paper backed fiberglass bats in the walls.
The outside of the house is stucco and the inside is drywall. I can't figure how to backfill those walls without tearing out the interior walls.

Anyone got any ideas?

[S-F]

Cut hols, blow cellulose. I do it all the time.

[strider3700]

will that work without removing the old fiberglass? I figured what's in there will just sag and jam the filling.

[S-F]

It can be done. Like I said, I do it all the time. It takes a little bit of skill because you can end up with all the fiberglass bunched up at the top of the bay. If your blowing from the inside you'd need to make sure you don't break the kraft paper. Just slide the hose up between it and the drywall. If it were my house I'd either just leave the fiberglass in there or I'd cut long strips of drywall out and pull it out. Ultimately I'd end up doing the latter. You can't fill the cavity completely with cellulose, obviously, because there is already fiberglass in there and compressed fiberglass has little R value. For some reason, though, auditors will occasionally spec this kind of job, so I end up doing it. And a 2x4 cavity is usually filled with R 13. Not sure where the R 7 number came from.