U-Value and R-Value
Each layer resistance is calculated from thickness divided by thermal conductivity, or entered directly when a declared R-value is available. Surface and layer resistances are added before taking the reciprocal to obtain U-value.
Thermal Conductivity
Conductivity varies by product, density, moisture and design condition. The actual declared or design value should replace any generic convenience preset.
Surface Resistance
ISO 6946 surface resistance depends on heat-flow direction. The calculator provides standard wall, upward and downward choices and allows project-specific custom values in Advanced use.
Repeated Framing Paths
A timber or metal framing path can bypass part of the insulation. The optional framed mode reports the upper and lower resistance limits and the combined approximation instead of silently averaging U-values.
U-Value Calculator FAQ
What is a U-value?
U-value is the steady-state heat-transfer coefficient of an assembly in W/m²K. A lower U-value represents greater thermal resistance under the calculation assumptions.
What is the difference between U-value and R-value?
R-value measures thermal resistance. For a homogeneous multilayer assembly, U is the reciprocal of the total resistance including applicable surface resistances.
Which thermal conductivity should I use?
Use the declared or design conductivity for the actual product and project conditions. Generic material presets are examples only.
Can this calculator assess a floor touching the ground?
No. Ground-contact heat transfer requires a different method. Downward heat flow here applies only to an element exposed to air.
Does the temperature profile check condensation?
No. It is a simplified steady-state interface-temperature profile and does not assess vapour transport or condensation risk.
How is repeating framing represented?
The advanced method combines insulation and framing paths using upper and lower total-resistance limits, then uses their mean as an ISO-6946-style approximation.