U-Value Calculator
A 230 mm brick wall with 20 mm cement plaster on each face has a U-value of 1.96268 W/(m²·K).
Inside to outside.
Cement plaster 0.72, brick 0.81, dense concrete 1.6, mineral wool 0.035–0.04, XPS 0.03.
1.96268475890477 W/(m²·K)
Full answer, then cut to fewer decimals (not rounded):
- 1.96268475890477 W/(m²·K)
- 1.9626847589047 W/(m²·K)
- 1.962684758904 W/(m²·K)
- 1.96268475890 W/(m²·K)
- 1.9626847589 W/(m²·K)
- 1.962684758 W/(m²·K)
- 1.96268475 W/(m²·K)
- 1.9626847 W/(m²·K)
- 1.962684 W/(m²·K)
- 1.96268 W/(m²·K)
- 1.9626 W/(m²·K)
- 1.962 W/(m²·K)
- 1.96 W/(m²·K)
- 1.9 W/(m²·K)
- Total resistance R_T
- 0.5095061728 m²·K/W
- In US R-value
- 2.893110223 ft²·°F·h/BTU
- Heat flow U A ΔT
- 294.4027138 W
Step-by-step solution
- R of each layer = d/λ: 0.0277778, 0.283951, 0.0277778 m²·K/W
- R_T = R_si + Σd/λ + R_so = 0.5095061728 m²·K/W
- U = 1/R_T = 1.962684759 W/(m²·K)
U-Value Formula
U = 1 / (R_si + Σ d/λ + R_so)
R_si = 0.13, R_so = 0.04 m²·K/W for walls (ISO 6946)
Worked Example
A 230 mm brick wall plastered 20 mm on both faces:
- R of each layer = d/λ: 0.0277778, 0.283951, 0.0277778 m²·K/W
- R_T = R_si + Σd/λ + R_so = 0.5095061728 m²·K/W
- U = 1/R_T = 1.962684759 W/(m²·K)
In US R-value: 2.893110223 ft²·°F·h/BTU · Heat flow U A ΔT: 294.4027138 W
GATE tip
Thicknesses must be in metres inside d/λ: 230 mm brick at λ = 0.81 gives R = 0.284 m²·K/W.
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Frequently asked questions
Does a plain brick wall meet energy codes?
Rarely: energy codes such as ECBC set maximum U-values for walls well below the 2 W/(m²·K) of a plastered brick wall, so insulation or a cavity is usually needed.
How much does insulation help?
50 mm of mineral wool (λ = 0.04) adds 1.25 m²·K/W, cutting the brick wall’s U from about 2.0 to 0.57.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). U-Value Calculator. Retrieved October 29, 2026, from https://scientificconverters.com/calculators/u-value-calculator/
IEEE
Scientific Converters, "U-Value Calculator," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/calculators/u-value-calculator/