R-Value Table for Insulation and Roofing Materials
(Includes RSI Values)
Roof Online Staff
To learn more about R-value, see Roof Online’s R-Value page.
Table of Contents
- Building Codes and Roofs
- Building Insulation
- Energy Codes and Roofs
- R-Value and Roofs
- Types of Roof Insulation
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.
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)
|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)
|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|