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*
Location Heat Type Attic Wall Floor Crawl Space Wall** Basement Wall
Zone 1 Natural Gas 38-49 13 13 13 11
Oil Furnace 38-49 13 13 13 11
Electric Furnace 38-49 13 13 13 11
Electric Baseboard 38-49 13 13 13 11
Heat Pump 38-49 13 13 13 11
LPG Furnace 38-49 13 13 13 11
Zone 2 Natural Gas 38 13 13-19 13 11
Oil Furnace 38 13 13-19 13-25 11
Electric Furnace 38-49 13 19-25 25 11
Electric Baseboard 38-49 13 13-25 13-25 11
Heat Pump 38 13 13-19 13 11
LPG Furnace 38-49 13 19-30 25 11
Zone 3 Natural Gas 30-38 13 13-19 13-25 11
Oil Furnace 38 13 13-19 13 11
Electric Furnace 38 13 13-19 13-25 11
Electric Baseboard 38 13 13-19 13 11
Heat Pump 30-38 13 13 13 11
LPG Furnace 38-49 13 13-30 13-25 11
Zone 4 Natural Gas 38-49 13 25-30 25 11
Oil Furnace 49 13 30 25 11
Electric Furnace 38-49 13 25-30 25 25
Electric Baseboard 49 13 30 25 11
Heat Pump 38-49 13 13-25 13-25 11
LPG Furnace 49 13 30 25 11-25
Zone 5 Natural Gas 38 13 25 25 11
Oil Furnace 49 13 30 25 11-15
Electric Furnace 49 13 30 25 25
Electric Baseboard 49 13 30 25 11
Heat Pump 38 13 30 25 11
LPG Furnace 49 13 30 25 25
Zone 6-8 Natural Gas 49 13 30 25 25
Oil Furnace 49 13 30 25 25
Electric Furnace 49 13 30 25 25
Electric Baseboard 49 13 30 25 25
Heat Pump 49 13 30 25 25
LPG Furnace 49 13 30 25 25

*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
Material R-value/in 3 1/2″ 5 1/4″ 10″ 12″ 15″
Fiberglass (batt) 3.1 – 3.4 10.8 – 11.9 16.3 – 17.8 31.0 – 34.0 37.2 – 40.8 46.5 – 51.0
Fiberglass blown (attic) 2.2 – 4.3 7.7 – 15.0 11.5 – 22.6 22.0 – 43.0 26.4 – 51.6 33.0 – 64.5
Fiberglass blown (wall) 3.7 – 4.3 12.9 – 15.0 19.4 – 22.6 37.0 – 43.0 44.4 – 51.6 55.5 – 64.5
Mineral Wool (batt) 3.1 – 3.4 10.8 – 11.9 16.3 – 17.8 31.0 – 34.0 37.2 – 40.8 46.5 – 51.0
Mineral Wool blown (attic) 3.1 – 4.0 10.8 – 14.0 16.3 – 21.0 31.0 – 40.0 37.2 – 48.0 46.5 – 60.0
Mineral Wool blown (wall) 3.1 – 4.0 10.8 – 14.0 16.3 – 21.0 31.0 – 40.0 37.2 – 48.0 46.5 – 60.0
Cellulose blown (attic) 3.2 – 3.7 11.2 – 12.9 16.8 – 15.0 32.0 – 37.0 38.4 – 44.4 48.0 – 55.5
Cellulose blown (wall) 3.8 – 3.9 13.3 – 13.6 19.9 – 20.8 38.0 – 39.0 45.6 – 46.8 57.0 – 58.5
Polystrene Board 3.8 – 5.0 13.3 – 17.5 19.9 – 26.2 38.0 – 50.0 45.6 – 60.0 57.0 – 75.0
Polyurethane Board 5.5 – 6.5 19.2 – 22.7 28.9 – 34.1 55.0 – 65.0 66.0 – 78.0 82.5 – 97.5
Polyisocyanurate (foil-faced) 5.6 – 8.0 18.2 – 28.0 29.4 – 42.0 56.0 – 80.0 67.2 – 96.0 84.0 – 120.0
Open Cell Spray Foam 3.5 – 3.6 12.2 – 12.6 18.4 – 18.9 35.0 – 36.0 42.0 – 43.2 52.5 – 54.0
Closed Cell Spray Foam 6.0 – 6.5 21.0 – 22.7 31.5 – 34.1 60.0 – 65.0 72.0 – 78.0 90.0 – 97.5

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