Building science calculator
Multi-Layer Wall Heat Loss Calculator
Build a wall assembly from individual material layers. The calculator determines the resistance of each layer from thickness and thermal conductivity, adds optional surface resistances, and estimates steady-state transmission heat loss.
Wall and temperature inputs
Wall layers
Choose a representative material or enter a custom conductivity. Thickness is entered in millimetres and converted to metres for the calculation.
Assembly result
How the layers combine
Thermal resistances in a simple layered wall add because the same steady heat flow passes through each layer in sequence. A low-conductivity layer can provide a large share of the total resistance even when it is much thinner than masonry or concrete.
The calculator reports each layer's R-value so you can see which layers dominate the assembly. It also reports the U-value, which represents heat flow per square metre for each kelvin of temperature difference across the assembly.
Why a real wall can behave differently
Studs, metal ties, fasteners, slab edges and other repeating or local bridges create parallel heat-flow paths that a simple series model cannot represent. Air leakage can also move much more heat than conduction through the nominal wall layers. Use the Thermal Bridge Explorer to examine a simplified parallel-path case and the Room Heat Loss Calculator for a broader transmission estimate.
Related learning
Read Thermal Resistance, How Insulation Works, U-Value and Thermal Bridging for the concepts behind this calculation.