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About This R-Value Table

The following table provides typical R-values (and RSI) for various materials.

These R-values were taken from manufacturer technical data sheets and are the reported R-values per inch of actual products. In a few cases, the R-values we give were taken from a non-manufacturer source that we consider to be trustworthy and accurate.

In all cases, this table is intended only as a general guide to material R-values.

Check with the Manufacturer

When calculating the R-value for a real-life installation, always refer to the manufacturer's data sheets for the actual, specific product you intend to use, or contact the technical department of the product manufacturer or material provider.

R-Value vs. RSI

R-value is used in the United States. RSI (R-value Système International) is the metric equivalent.

To convert the R-value of a specific thickness of a material to RSI, divide the R-Value by 5.67826. To convert RSI to R-value, multiply the RSI by 5.67826. For example, two inches of extruded polystyrene, with an R-value of 11, has an RSI of 1.93721.

R-Value and Energy Codes

Please note that the R-values for roof membranes, shingles, tiles, air films, and roof deck materials will probably not be permitted by your local code to be included when total roof assembly R-value is being calculated for the purpose of satisfying energy code requirements.

Always check with your local code authority.

R-Value Chart

Note: While the R-Value for a material is typically given per inch, the RSI is typically given per millimeter, so please be aware that the R-Values and RSI values for the materials in the following table are not for equivalent thicknesses.

Note: The R-values given for roof coverings such as shingles or membranes are totals for typical installed thicknesses of those materials. They are not R-values per inch for the material.

R-Value of Roofing Materials and Building Insulation
Material R-Value per Inch (ft²·°F·hr/BTU) RSI per Millimeter (K·m²/W) R-Value for TYPICAL INSTALLED Thickness
(NOT per Inch)		 Source
Asphalt Shingles 0.44 National Roofing Contractors Association
Built-up Roof Membrane, Gravel-Surfaced (Membrane and Gravel Only) 0.33 National Roofing Contractors Association
Built-up Roof Membrane, Smooth-Surfaced (Membrane Only) 0.24 National Roofing Contractors Association
Cellulose, Blown (Attic) 3.8 0.02638 Cellulose Insulation Manufacturers Association
Cellulose, Blown (Wall) 3.8 0.02638 Cellulose Insulation Manufacturers Association
Cellulose, Wet Spray 3.75 0.02598 International Cellulose Corporation
Concrete, Lightweight Insulating 0.90 - 1.49 0.00630 - 0.01024 Siplast
Concrete, Structural (140 pcf) 0.08 0.00040 Siplast
EPDM Roof Membrane, Ballasted (Membrane and Ballast Only) 0.33 National Roofing Contractors Association
EPDM Roof Membrane, Fully-Adhered or Mechanically-Attached (Membrane Only) 0.24 National Roofing Contractors Association
Fiber Cement Shingles 0.21 National Roofing Contractors Association
Fiberglass, Batt 3.14 - 4.29 0.02165 - 0.02992 Johns Manville
Fiberglass, Blown (Attic) 2.12 - 4.0 0.01457 - 0.02756 Johns Manville
Fiberglass, Blown (Wall) 4.0 - 4.3 0.02756 - 0.02992 Johns Manville
Fiberglass, Rigid Board 4.3 - 4.5 0.02992 - 0.03110 Johns Manville
Gypsum Board 0.90 - 1.12 0.00630 - 0.00787 United States Gypsum Company; Georgia-Pacific
Metal Roof Panels No Useful R-Value National Roofing Contractors Association
Mineral Wool, Batt 4.0 - 4.22 0.02756 - 0.02913 Owens Corning
Mineral Wool, Blown (Attic) 2.95 - 3.39 0.02047 - 0.02362 Owens Corning; American Rockwool Manufacturing
Mineral Wool (Rigid Board) 3.8 0.02638 Rockwool Group
Modified Bitumen Roof Membrane, Granule-Surfaced (Membrane Only) 0.15 National Roofing Contractors Association
Oriented Strand Board (OSB) 1.0 - 1.24 0.00709 - 0.00866 Minnesota Sustainable Housing Initiative
Perlite Cover Board 2.64 0.01811 Johns Manville
Phenolic Foam Board 6.7 - 7.5 0.04646 - 0.05197 Dow Chemical Company
Plywood 1.0 - 1.24 0.00709 - 0.00866 Minnesota Sustainable Housing Initiative
Polyiso Insulation (Polyisocyanurate) 5.0 (NRCA)
5.7 (PIMA)		 0.03465 (NRCA)
0.03937 (PIMA)		 National Roofing Contractors Association;
Polyisocyanurate Insulation Manufacturers Association
Polystyrene, Expanded (EPS) 3.85 - 4.5 0.02677 - 0.03110 Insulation Technology, Inc.; ACH Foam Technologies
Polystyrene, Extruded (XPS) 5.0 - 5.5 0.03465 - 0.03819 XPSA (Extruded Polystyrene Foam Association)
PVC Roof Membrane, Fully-Adhered or Mechanically-Attached (Membrane Only) 0.24 National Roofing Contractors Association
Slate Roofing 0.05 National Roofing Contractors Association
Sprayed Polyurethane Foam (Closed Cell)) 4.9 - 7.1 0.03386 - 0.04921 Icynene, Inc.
Sprayed Polyurethane Foam (Open Cell) 3.7 - 4.0 0.02559 - 0.02756 Icynene, Inc.
Tile Roofing, Including Batten System and Air Space 2.95 Boral Roofing
TPO Roof Membrane, Fully-Adhered or Mechanically-Attached (Membrane Only) 0.24 National Roofing Contractors Association
Wood Fiberboard 2.5 0.01732 Blue Ridge Fiberboard, Inc
Wood Shakes and Shingles 0.94 National Roofing Contractors Association
Wood (Typical Hardwood) 0.7 0.00472 U.S. Department of Energy
Wood (Typical Softwood) 1.4 0.00984 U.S. Department of Energy