What is the max depth of faced fiberglass insulation that I can stuff into a 2x4 frame wall? What would be the max R value that I can purchase? Thank you !

 

R-13 fiberglass is sized for a 2x4 wall. They do make a high density fiberglass batt rated at R-15. Trying to stuff more than that into the wall actually reduces the total R-value as compressed fiberglass will lose its effectiveness. To get more R-value than that you would need to shift to a spray in foam or rigid foam boards. The next step would be to cover the inside surface with a layer of rigid before the drywall goes up. When the studs are calculated into the whole wall assemble, R-13 insulation results in about a R-8 wall.

An additional step would be to seal (caulk or foam) all cracks and holes to eliminate as much air leakage as possible.

Bud

PS neatness counts. No extra spaces or voids does make a difference.

 

Also electrical boxes need to be well sealed for air movement. Even just pulling vapor barrier behind the box and tape sealing it to the existing poly will help alot if this has not been done in the past. Alot of air will flow through these boxes if not properly sealed. Sealing with spray foam is even a better way.