R-Value Converter (US R to RSI, m²·K/W)
R-Value Converter (US R to RSI, m²·K/W): convert between 5 thermal resistance (r-value) units, for example 1 ft²·°F·h/BTU = 0.1761101837 m²·K/W.
| Unit | Value |
|---|---|
| US R-value to square metre kelvin per watt | 0.1761101837 m²·K/W |
| US R-value (ft²·°F·h/BTU) | 1 ft²·°F·h/BTU |
| US R-value to square metre hour degree Celsius per kilocalorie | 0.2048161436 m²·h·°C/kcal |
| US R-value to clo | 1.136194733 clo |
| US R-value to tog | 1.761101837 tog |
Convert insulation R-values between US R (ft²·°F·h/BTU), RSI (m²·K/W), clo, tog and m²·h·°C/kcal. US R-1 = RSI 0.17611, so R-13 is RSI 2.29 and RSI 1 is R-5.68.
R-value and U-value
For layers in series add the R-values (plus inside and outside surface resistances) and take U = 1/ΣR. A wall with ΣR = 2.5 m²·K/W has U = 0.4 W/(m²·K). R of one layer = thickness ÷ conductivity: 100 mm of λ = 0.04 W/(m·K) insulation gives RSI 2.5.
Thermal Resistance (R-value) unit definitions
- square metre kelvin per watt (m²·K/W)
- The square metre kelvin per watt (RSI) is the SI unit of thermal resistance of a building element: R = d/λ for each layer, and the U-value is 1/ΣR. ECBC and the EU specify wall and roof insulation in m²·K/W.
- US R-value (ft²·°F·h/BTU)
- The US R-value, in ft²·°F·h/BTU, is the number printed on US insulation: R-13 for a 2×4 wall, R-38 to R-49 for attics. One US R unit is 0.17611 m²·K/W, so R-13 ≈ RSI 2.29.
- clo (clo)
- The clo measures the thermal insulation of clothing: 1 clo (0.155 m²·K/W) keeps a resting person comfortable at about 21 °C. Summer clothing is about 0.5 clo, a business suit 1 clo.
- tog (tog)
- The tog is the British unit of textile and bedding insulation, 0.1 m²·K/W: summer duvets are 4.5 tog, winter duvets 13.5 tog, and 1 clo = 1.55 tog.
- square metre hour degree Celsius per kilocalorie (m²·h·°C/kcal)
- Square metre hour degree Celsius per kilocalorie is the old MKS unit of thermal resistance found in pre-SI Indian and European building texts. Reference: International Table kilocalorie (4186.8 J).
Popular thermal resistance (r-value) conversions
Show all 20 thermal resistance (r-value) conversions
From square metre kelvin per watt
From US R-value
From square metre hour degree Celsius per kilocalorie
From clo
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Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures.
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology.
Last reviewed: .