R-values of Insulation and Other Building Materials
There are tables of building material R-Values further down in this article, but first we should quickly cover some basics about R-Values, U-factors, and calculating thermal resistance.
What are R-values?
In construction, the R-value is the measurement of a material’s capacity to resist heat flow from one side to the other. In simple terms, R-values measure the effectiveness of insulation and a higher number represents more effective insulation.
R-values of layers stacked in series are additive. Where heat has parallel paths, such as studs next to insulation, you cannot simply add R-values. Instead, you need to follow the parallel path method by computing each path’s U-factor, weight them by area, and then invert to get the overall R-value of the assembly.
R-value Units
As we said before, the R-value measures the thermal resistance of a material. This can also be expressed as the temperature difference that will cause one unit of heat to pass through one unit of area over a period of time.
The two equations above are used to calculate the R-value of a material. Keep in mind that, due to the units, the Imperial R-value will be quite a bit larger than the SI R-value so it is important to determine the units used when working internationally. The charts below use Imperial Units since our website is focused on the North American market.
Use our free Wall R-Value Calculator to determine the estimated thermal resistance of a wall assembly.
What are U-factors?
Many energy modeling programs and code calculations require U-factors (sometimes called U-values) of assemblies. The U-factor is the heat transfer coefficient, which simply means that it is a measure of an assembly’s capacity to transfer thermal energy across its thickness. The U-factor of an assembly is the reciprocal of the total R-value of the assembly. The equation is shown below.
Tables of Building Material R-values
The R-values for specific assemblies like doors and glazing in the table below are generalizations because they can vary significantly based on special materials that the manufacturer uses. For instance, using argon gas in a double pane insulating glass unit will improve the R-value, as will low-emissivity coatings on glass panes. Consult manufacturer literature for values specific to your project.
Air Films and Air Spaces
| AIR FILMS | R-VALUE (ft²·°F·h/Btu) |
|---|---|
| Exterior, 15-mph wind (winter) | 0.17 |
| Exterior, 7.5-mph wind (summer) | 0.25 |
| Interior Wall Air Film (heat flow horizontal) | 0.68 |
| Interior Ceiling Air Film (heat flow up) | 0.61 |
| Interior Ceiling or Floor Air Film (heat flow down) | 0.92 |
Air-space R-values depend on the emissivity of the surfaces facing the space, the direction of heat flow and the temperature. A foil-faced space can be two to three times as effective. Ventilated spaces, such as rainscreen cavities, get no credit.
| AIR SPACE | R-VALUE (ft²·°F·h/Btu) |
|---|---|
| Minimum 1/2″ up to 4″ Air Space (for non-reflective vertical wall cavities) | 0.90 – 1.00 |
Insulating Materials
| RIGID BOARD INSULATION | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Expanded Polystyrene (EPS) | per inch | 3.60 – 4.20 |
| Extruded Polystyrene (XPS) | per inch | 5.00 |
| Polyiso (Foil Faced) – wall board, aged | per inch | 6.00 – 6.50 |
| Mineral wool board (stone wool, 4–8 pcf) | per inch | 4.00 |
| BATT INSULATION | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Fiberglass batt R-11 | 3-1/2″ | 11.00 |
| Fiberglass batt R-13 | 3-1/2″ | 13.00 |
| Fiberglass batt R-15 (high density) | 3-1/2″ | 15.00 |
| Fiberglass batt R-19 | 6-1/4″ – 6-1/2″ | 19.00 |
| Fiberglass batt R-21 (high density) | 5-1/2″ | 21.00 |
| Fiberglass batt R-30 | 9-1/2″ – 10-1/4″ | 30.00 |
| Fiberglass batt R-38 | 12″ | 38.00 |
| Mineral Wool batt R-15 | 3-1/2″ | 15.00 |
| Mineral Wool batt R-23 | 5-1/2″ | 23.00 |
| FOAM INSULATION (FOAMED ON SITE) | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Polyurethane Foam – Closed Cell | per inch | ~6.00 |
| Polyurethane Foam – Open Cell | per inch | ~3.70 |
| LOOSE FILL INSULATION | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Cellulose, dense-pack | per inch | 3.20 – 3.80 |
| Cellulose, loose-fill attic | per inch | 3.20 – 3.80 |
| Vermiculite (WARNING: may contain asbestos) | per inch | ~2.13 |
The table below reflects the effective R-value of the insulation and framing layer, not an insulating material. See the note on ASHRAE 90.1-2022 Addendum aw.
| INSULATION WITH METAL STUD FRAMING Effective R-Value of the framing/insulation layer | EFFECTIVE R-VALUE (ft²·°F·h/Btu) |
|---|---|
| R-11 Mineral Fiber with 2×4 metal studs @ 16″ OC | 5.50 |
| R-11 Mineral Fiber with 2×4 metal studs @ 24″ OC | 6.60 |
| R-19 Mineral Fiber with 2×6 metal studs @ 16″ OC | 7.10 |
| R-19 Mineral Fiber with 2×6 metal studs @ 24″ OC | 8.55 |
Interior Wall Finishes
| MATERIAL | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Gypsum Wall Board | 1/2″ | 0.45 |
| Gypsum Wall Board | 5/8″ | 0.56 |
| Medium Density Particle Board | 1/2″ | 0.53 |
Exterior Sheathing
| MATERIAL | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| OSB (Oriented Strand Board) | 7/16″ | 0.62 |
| OSB (Oriented Strand Board) | 1/2″ | 0.68 |
| Plywood, Generic Softwood | 1/2″ | 0.62 |
| Plywood, Douglas Fir | 1/2″ | 0.79 |
| Gypsum Sheathing, Generic | 1/2″ | 0.45 |
| Glass-mat Gypsum Sheathing | 1/2″ | 0.56 |
| Fiber Board Sheathing | 1/2″ | 1.32 |
Exterior Cladding and Roofing
| CLADDING MATERIAL | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Aluminum / Vinyl Siding (not insulated) | 0.61 | |
| Aluminum / Vinyl Siding (3/8″ insulation) | 1.82 | |
| Fiber-Cement Siding | 5/16″ | 0.15 |
| Stucco, Cement Plaster | 7/8″ | 0.18 |
| Stucco, Cement Plaster | 3/4″ | 0.15 |
| ROOFING MATERIAL | R-VALUE (ft²·°F·h/Btu) |
|---|---|
| Asphalt shingles | 0.44 |
| Wood shingles | 0.94 |
Concrete, Masonry, Stone
| CONCRETE | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Concrete 60 pounds per cubic foot | per inch | 0.48 |
| Concrete 70 pounds per cubic foot | per inch | 0.40 |
| Concrete 80 pounds per cubic foot | per inch | 0.33 |
| Concrete 100 pounds per cubic foot | per inch | 0.21 |
| Concrete 120 pounds per cubic foot | per inch | 0.13 |
| Concrete 150 pounds per cubic foot | per inch | 0.07 |
| MASONRY | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Clay Brick | 3-5/8″ | 0.54 |
| Concrete Masonry Unit (CMU) – hollow core | 4″ | 0.80 |
| Concrete Masonry Unit (CMU) – hollow core | 8″ | 1.11 |
| Concrete Masonry Unit (CMU) – hollow core | 12″ | 1.23 |
| STONE | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Granite | per inch | 0.05 |
| Sandstone | per inch | 0.04 |
| Limestone | per inch | 0.06 |
Flooring
| MATERIAL | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Hardwood | 3/4″ | 0.68 |
| Resilient Tile (vinyl, rubber) | 0.05 | |
| Carpet with 3/4″ urethane pad | 2.38 |
Glazing
Every value in the following glazing table is an inverted center-of-glass U-factor for uncoated clear glass, with air films included. However, exterior glazing is rarely used without any coatings. The table is being provided for historical reference.
Use the NFRC-rated whole-product U-factor for your specific windows.
| GLAZING – UNCOATED CLEAR – HISTORICAL (CENTER OF GLASS 1/U VALUE) | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Single Pane | 1/4″ | 0.90 |
| Double Pane with 1/4″ air space | 1.75 | |
| Double Pane with 1/2″ air space | 2.04 | |
| Triple Pane with 1/4″ air spaces | 2.63 | |
| Triple Pane with 1/2″ air spaces | 3.23 |
Doors
| DOORS | THICKNESS | R-VALUE (ft²·°F·h/Btu) |
|---|---|---|
| Wood, 1-3/4″ hollow core | 1.75″ | 2.17 |
| Wood, 1-3/4″ solid core | 1.75″ | 2.50 |
| Solid insulated metal door, polystyrene insulation ASTM C518 Calculated | 1.5″ – 2″ | 6.00 – 6.40 |
| Solid insulated metal door, polystyrene insulation ASTM C1363 Operable | 1.5″ – 2″ | 2.20 – 2.90 |
| Solid insulated metal door, polyurethane insulation ASTM C518 Calculated | 1.5″ – 2″ | 10.00 – 11.00 |
| Solid insulated metal door, polyurethane insulation ASTM C1363 Operable | 1.5″ – 2″ | 2.40 – 3.50 |
In the chart above, you will notice that there are two vastly different R-values provided for insulated metal doors with polyurethane insulation. Based on ASTM C518 (Calculation Method) the door has an R-value of up to 11, but using ASTM C1363 (Tested/Operable) the same door only has an R-value of up to 3.5. This is a huge difference and essentially comes down to ASTM C518 being a theoretical maximum based on a steady-state thermal test of only a portion of the door panel. However, we all know that the frame, gasketing, and, hardware will significantly affect the thermal transmittance. So a new standard test has been implemented, ASTM C1363, which tests the entire door assembly including the frame and hardware.
The results of ASTM C1363 are much lower, but are much more accurate to the actual installed conditions. In fact, the doors are performing the same as before – it is just that the R-values are much more in line with how the door really performs. Many architects are now specifying doors with the ASTM C1363 test as the standard for thermal transmittance. It is expected that other products will follow suit.
For more information, check out the Steel Door Institute’s article Why Have Thermal Performance Ratings Changed?
Sources
The values in the tables above were taken from a number of sources including:
ASHRAE Handbook—Fundamentals (1997), Chapter 24: Thermal and Water Vapor Transmission Data
ASHRAE Handbook—Fundamentals (2009), Chapter 26, Table 4 (reproduced in ASHRAE Errata to Principles of HVAC, 6th ed.)
ASHRAE Handbook—Fundamentals (1993), Chapter 27: Fenestration
ASHRAE 90.1 Appendix A9.4: Calculation Procedures and Assumptions (air films)
ASHRAE 90.1 Appendix A9.4.2: Air Spaces
ANSI/ASHRAE/IES Addendum aw to Standard 90.1-2022
Washington State Energy Code WAC 51-11C-610336: Effective R-Values for Metal Framing and Cavity
Seattle Energy Code A103.3.6.2: Metal Stud Wall Effective R-Values
Natural Resources Canada: Tables for Calculating Effective Thermal Resistance of Opaque Assemblies
California Energy Commission: Joint Appendix JA4, U-Factor, C-Factor and Thermal Mass Data
EPS Industry Alliance: ASTM C578 EPS Thermal Insulation Performance Requirements
Professional Roofing: Tech Today (May 2011)
Brick Industry Association Technical Note 4: Introduction to Energy Performance of Brick Masonry
Spray Polyurethane Foam Alliance: FAQs
Building America Solution Center: Closed-Cell and Open-Cell Spray Foam R-Values
Building America Solution Center: Dense-Pack Insulation
CMHA TEK 6-2C: R-Values and U-Factors of Single Wythe Concrete Masonry Walls
Steel Door Institute: Why Have Thermal Performance Ratings Changed?
National Fenestration Rating Council
Various Manufacturer Websites and Product Data
Help make Archtoolbox better for everyone. If you found an error or out of date information in this article (even if it is just a minor typo), please let us know.
