Cellulose Insulation

Cellulose, a plant-based insulator, is the oldest form of home insulation and, at times, has been produced from sawdust, cotton, straw, hemp, and other plant materials with low thermal-conductivity. Today, it is produced from recycled newspapers that are later treated with chemicals that reduce its ignition potential.

It became popular in the 1970s due to the oil crisis, although it suffered from competition with fiberglass insulation as a result of fire-standards lobbying by the fiberglass and mineral companies. Cellulose must be chemically treated in order to reduce its flammable properties, although it always has the potential to burn. These chemicals, usually sodium borate, boric acid, or ammonium sulfate, are generally considered safe for human contact.

This material provides a number of advantages over fiberglass – it is inexpensive, significantly reduces airflow, and is not believed to pose any serious health risks.

It is possible that the material can produce harmful off-gasses from the ink contained in the newspapers, but insulation is generally contained in sealed locations, so this is not likely to be a health concern. As is true with fiberglass, protect your lungs with a breathing mask when handling cellulose insulation.

Fiberglass and cellulose are both used as insulators, although they offer somewhat different advantages. Also, keep in mind that there are other types of thermal insulation available that are not covered in this article, such as rock wool, vermiculite, and various two-part foams.

Insulation R Value Chart

Insulation R-Values for Location, Heat Type & Area*
LocationHeat TypeAtticWall FloorCrawl Space Wall**Basement Wall
Zone 1Natural Gas38-4913131311
Oil Furnace38-4913131311
Electric Furnace38-4913131311
Electric Baseboard38-4913131311
Heat Pump38-4913131311
LPG Furnace38-4913131311
Zone 2Natural Gas381313-191311
Oil Furnace381313-1913-2511
Electric Furnace38-491319-252511
Electric Baseboard38-491313-2513-2511
Heat Pump381313-191311
LPG Furnace38-491319-302511
Zone 3Natural Gas30-381313-1913-2511
Oil Furnace381313-191311
Electric Furnace381313-1913-2511
Electric Baseboard381313-191311
Heat Pump30-3813131311
LPG Furnace38-491313-3013-2511
Zone 4Natural Gas38-491325-302511
Oil Furnace4913302511
Electric Furnace38-491325-302525
Electric Baseboard4913302511
Heat Pump38-491313-2513-2511
LPG Furnace4913302511-25
Zone 5Natural Gas3813252511
Oil Furnace4913302511-15
Electric Furnace4913302525
Electric Baseboard4913302511
Heat Pump3813302511
LPG Furnace4913302525
Zone 6-8Natural Gas4913302525
Oil Furnace4913302525
Electric Furnace4913302525
Electric Baseboard4913302525
Heat Pump4913302525
LPG Furnace4913302525

*Ranges resulted from the slection of two different zip codes within the same zone (i.e. Dover, DE and Chattanouga,TN for zone 4)

R-value of Materials and Depths
MaterialR-value/in3 1/2″5 1/4″10″12″15″
Fiberglass (batt)3.1 – 3.410.8 – 11.916.3 – 17.831.0 – 34.037.2 – 40.846.5 – 51.0
Fiberglass blown (attic)2.2 – 4.37.7 – 15.011.5 – 22.622.0 – 43.026.4 – 51.633.0 – 64.5
Fiberglass blown (wall)3.7 – 4.312.9 – 15.019.4 – 22.637.0 – 43.044.4 – 51.655.5 – 64.5
Mineral Wool (batt)3.1 – 3.410.8 – 11.916.3 – 17.831.0 – 34.037.2 – 40.846.5 – 51.0
Mineral Wool blown (attic)3.1 – 4.010.8 – 14.016.3 – 21.031.0 – 40.037.2 – 48.046.5 – 60.0
Mineral Wool blown (wall)3.1 – 4.010.8 – 14.016.3 – 21.031.0 – 40.037.2 – 48.046.5 – 60.0
Cellulose blown (attic)3.2 – 3.711.2 – 12.916.8 – 15.032.0 – 37.038.4 – 44.448.0 – 55.5
Cellulose blown (wall)3.8 – 3.913.3 – 13.619.9 – 20.838.0 – 39.045.6 – 46.857.0 – 58.5
Polystrene Board3.8 – 5.013.3 – 17.519.9 – 26.238.0 – 50.045.6 – 60.057.0 – 75.0
Polyurethane Board5.5 – 6.519.2 – 22.728.9 – 34.155.0 – 65.066.0 – 78.082.5 – 97.5
Polyisocyanurate (foil-faced)5.6 – 8.018.2 – 28.029.4 – 42.056.0 – 80.067.2 – 96.084.0 – 120.0
Open Cell Spray Foam3.5 – 3.612.2 – 12.618.4 – 18.935.0 – 36.042.0 – 43.252.5 – 54.0
Closed Cell Spray Foam6.0 – 6.521.0 – 22.731.5 – 34.160.0 – 65.072.0 – 78.090.0 – 97.5

**Crawl space walls that are vented or have moist problems should not be insulated.