Drawing No. EH–BE–002 // Building Energy & Services
Insulation / U-Value / R-Value Calculator
Reviewed August 2026
Build your wall or roof layer by layer, see exactly where the thermal resistance comes from, and turn a technical U-value into practical heat-loss and condensation information.
01 // Build the assembly
02 // Envelope performance
Background & method
ISO 6946 provides calculation methods for thermal resistance and transmittance of building elements made from thermally homogeneous layers and some inhomogeneous constructions. This consumer-oriented tool focuses on the transparent homogeneous-layer method and adds practical surface-temperature and upgrade calculations.
FAQ
R-value measures resistance to heat flow; higher is better. U-value is thermal transmittance, approximately the inverse of total resistance; lower is better.
Heat transfer includes boundary-layer resistance at the indoor and outdoor surfaces as well as conduction through the material layers.
No. The main layer stack is one-dimensional. Studs, slab edges, lintels, balconies, metal fixings and other bridges can raise whole-element U-value and lower local surface temperature.
It compares the calculated inside surface temperature with the indoor-air dew point. A negative margin indicates possible surface condensation, while a small positive margin can still be vulnerable at thermal bridges.
Yes. Enter a target U-value and choose an insulation material; the calculator estimates the extra thickness required in a simple homogeneous layer model.