Johns Manville Formaldehyde-Free™ Fiberglass Insulation (Specific for 2" by 12" WOOD framed walls with joists spaced 24" apart) R-Value: 40 Dimensions: 11¼" x 24" Coverage: 48.00 sq. ft./bag Application: Attics JM Formaldehyde-Free™ fiberglass insulation promotes better indoor air quality, provides superior thermal efficiency and a reduction in sound. Data Sheet