R-Value Chart

Insulation Materials and their R-Values

"Commonly Used Insulations" Table 1

Insulation Type

R-Value Per Inch

Made From

Comments

Cellulose

3.5 - 3.7

Ground wood or paper

  • Often blown in attics and wails

  • Additives provide resistance to fire and mold/fungus growth

Fiberglass batt

3.0 - 3.8

Strands of molten glass

  • Fits best in standard joist widths

  • Fire and mold resistant

Fiberglass loose-fill

2.2 - 3.0

Strands of molten glass

  • Eye, sun, and throat irritant at time of installation

  • Lightest loosefill insulation

Rockwool ormineral wool

2.7 - 3.0

Molten rock or slag

  • Fire and mold resistant

  • Can irritate sun, eyes, and throat-High fire resistance

  • Available in blankets or batts

Rigid Board expanded polystyrene

4.0

Petrochemical

  • Can irritate skin, eyes, and throat

  • Often white "beadboard" material

  • Can absorb water, best used inside

  • Bums with toxic smoke

  • Needs fire barrier if used inside the home

Rigid Boardextrudedpolystyrene

4.6 - 5.0

Petrochemical

  • Water resistant Good for exterior use and below grade

  • Needs fire barrier if used inside

  • Serves as a vapor barrier

Rigid Board polyurethane or isocyanurate

6.0 - 8.7

Petrochemical

  • Often used as exterior sheathing, but not below grade

  • Absorbs water

  • Generally foil faced on both sides

  • Foil serves as a vapor barrier

Vermiculite

2.2

Silicate minerals

  • Non-combustible. Non-irritating

  • Rarely used now in attics, Heavy

  • Good for chimney flue insulation

WoodShavings

2.5

-

  • Hard to treat against fire, vermin, and fungal growth

  • May be too heavy for some attics

Information Provided by U.S. Department of Energy