Johns Manville Formaldehyde-Free™ Fiberglass Insulation (Specific for 2" by 4" WOOD framed walls with joists spaced 23" apart) R-Value: 12 Dimensions: 3½" x 23" Coverage: 150.14 sq. ft./bag Application: Interior Walls JM Formaldehyde-Free™ fiberglass insulation promotes better indoor air quality, provides superior thermal efficiency and a reduction in sound. Data Sheet