There is a table 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?
- R-value Units
- What are U-factors?
- Tables of Building Material R-values
- Doors and Assemblies
What are R-values?
In construction, the R-value is the measurement of a material's capacity toresist heat flowfrom 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 are additive. For instance if you have a material with an R-value of 12 attached to another material with an R-value of 3, then both materials combined have an R-value of 15.
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 smaller 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.
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 is is a measure of an assembly's capacity totransferthermal 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 dramatically improve the R-value. Consult manufacturer literature for values specific to your project.
| AIR FILMS | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BTU) |
|---|---|---|
| Exterior Air Film | 0.17 | |
| Interior Wall Air Film | 0.68 | |
| Interior Ceiling Air Film | 0.61 |
| AIR SPACE | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BTU) |
|---|---|---|
| Minimum 1/2" up to 4" Air Space | 1.00 |
| BUILDING BOARD | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BTU) |
|---|---|---|
| Gypsum Wall Board | 1/2" | 0.45 |
| Gypsum Wall Board | 5/8" | 0.5625 |
| Plywood | 1/2" | 0.62 |
| Plywood | 1" | 1.25 |
| Fiber board sheathing | 1/2" | 1.32 |
| Medium Density Particle Board | 1/2" | 0.53 |
| INSULATING MATERIALS | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BTU) |
|---|---|---|
| R-11 Mineral Fiber with 2x4 metal studs @ 16" OC | 5.50 | |
| R-11 Mineral Fiber with 2x4 wood studs @ 16" OC | 12.44 | |
| R-11 Mineral Fiber with 2x4 metal studs @ 24" OC | 6.60 | |
| R-19 Mineral Fiber with 2x6 metal studs @ 16" OC | 7.10 | |
| R-19 Mineral Fiber with 2x6 metal studs @ 24" OC | 8.55 | |
| R-19 Mineral Fiber with 2x6 wood studs @ 24" OC | 19.11 | |
| Expanded Polystyrene (Extruded) | 1" | 5.00 |
| Polyurethane Foam (Foamed on site) | 1" | 6.25 |
| Polyisocyanurate (Foil Faced) | 1" | 7.20 |
| Vermiculite (WARNING: may contain asbestos) | 1" | ~2.13 |
| MASONRY AND CONCRETE | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BTU) |
|---|---|---|
| Common Brick | 4" | 0.80 |
| Face Brick | 4" | 0.44 |
| Concrete Masonry Unit (CMU) | 4" | 0.80 |
| Concrete Masonry Unit (CMU) | 8" | 1.11 |
| Concrete Masonry Unit (CMU) | 12" | 1.28 |
| Concrete 60 pounds per cubic foot | 1" | 0.52 |
| Concrete 70 pounds per cubic foot | 1" | 0.42 |
| Concrete 80 pounds per cubic foot | 1" | 0.33 |
| Concrete 90 pounds per cubic foot | 1" | 0.26 |
| Concrete 100 pounds per cubic foot | 1" | 0.21 |
| Concrete 120 pounds per cubic foot | 1" | 0.13 |
| Concrete 150 pounds per cubic foot | 1" | 0.07 |
| Granite | 1" | 0.05 |
| Sandstone / Limestone | 1" | 0.08 |
| SIDING | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BT |
|---|---|---|
| Aluminum / Vinyl Siding (not insulated) | 0.61 | |
| Aluminum / Vinyl Siding (1/2" insulation) | 1.80 |
| FLOORING | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BT |
|---|---|---|
| Hardwood | 3/4" | 0.68 |
| Tile | 0.05 | |
| Carpet with fiber pad | 2.08 | |
| Carpet with rubber pad | 1.23 |
| ROOFING | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BT |
|---|---|---|
| Asphalt Shingles | 0.44 | |
| Wood Shingles | 0.97 |
| GLAZING | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BT |
|---|---|---|
| Single Pane | 1/4" | 0.91 |
| Double Pane with 1/4" air space | 1.69 | |
| Double Pane with 1/2" air space | 2.04 | |
| Double Pane with 3/4" air space | 2.38 | |
| Triple Pane with 1/4" air spaces | 2.56 | |
| Triple Pane with 1/2" air spaces | 3.23 |
| DOORS (see below) | THICKNESS | R-VALUE (F° · SQ.FT. · HR/BT |
|---|---|---|
| Wood, solid core | 1.75" | 2.17 |
| Solid insulated metal door, polystyrene insulation ASTM C518 Calculated | 1.5" - 2" | 6.00 - 7.00 |
| Solid insulated metal door, polystyrene insulation ASTM C1363 Operable | 1.5" - 2" | 2.20 - 2.80 |
| 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" | 2.50 - 3.50 |
The values in the table above were taken from a number of sources including: theASHRAE Handbook of Fundamentals,ColoradoENERGY.org, andBuilding Construction Illustratedby Francis D.K. Ching. Other minor sources were also used. Archtoolbox does not test materials or assemblies.
Doors and Assemblies
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 have 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 articleWhy Have Thermal Performance Ratings Changed?
Article Updated: February 27, 2022
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