HOW MUCH INSULATION DO YOU NEED?

Recommended Specifications by Insulation Type - Based on recommended R-38 in Attic

  Cellulose Fiberglass Rock Wool
R-value/inch 3.2 - 3.8 2.2 - 2.7 3.0 -  3.3
Inches (cm) needed for R-38 10 - 12     (25 - 30) 14 - 17    (35 - 43) 11.5 - 13  (29 - 33)
Density in lb/ft 3 (kg/m 3 ) 1.5 - 2.0   (24 - 36) 0.5 - 1.0  (10 - 14) 1.7            (27)
Weight at R-38 in lb/ft 2 (kg/m 2 ) 1.25 - 2.0   (6 10) 0.5 - 1.2   (3 - 6) 1.6 - 1.8    (8 - 9)
Average savings on energy bills 38% - 44% 16%-19% 29%-35%
Associated Health Risks No Yes Yes
Substantial Recycled Materials (75% or more recycled materials used) Yes No No
Significant Pollution during MFG No Yes Yes
Environmentally Sustainable Yes No No

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U.S. Department of Energy Recommendations