Kingspan U-value Calculator
Calculate thermal transmittance for your build
Select the type of construction element
Enter layers from outside to inside. Include all materials.
The U-value you aim to achieve for compliance
U-value Results
Thermal transmittance analysis
Enter your construction layers, then click Calculate to determine the U-value and see if it meets your target for energy efficiency.
U-value FAQ
Answers to the most common questions about U-values, thermal performance, and using this calculator for your project.
A U-value, or thermal transmittance, measures how effectively a building element (like a wall, roof, or floor) prevents heat from escaping. It is expressed in Watts per square metre per Kelvin (W/m²K). The lower the U-value, the better the insulating performance of the construction.
Low U-values are crucial for energy efficiency, reducing heating costs, and improving occupant comfort. They are a key requirement in modern building regulations worldwide to minimize heat loss and carbon emissions from buildings.
U-value is calculated as the inverse of the total thermal resistance (R-value) of all layers in a building element, including internal and external surface resistances. The formula is U = 1 / (R_total), where R_total is the sum of the R-values of each material layer plus surface resistances.
R-value measures a material’s resistance to heat flow—the higher the R-value, the better the insulator. U-value measures the overall rate of heat transfer through an entire assembly—the lower the U-value, the better the assembly insulates. They are reciprocals: U = 1/R.
Target U-values vary by region and building type, but common benchmarks for new UK builds are approximately: Walls: 0.18 W/m²K, Roofs: 0.11 W/m²K, and Floors: 0.13 W/m²K. Always consult the latest local building regulations for specific requirements.
This calculator allows you to input the layers of your wall, roof, or floor construction, including their thickness and thermal conductivity (lambda value). It then computes the total R-value and the resulting U-value, helping you select the right Kingspan product and thickness to meet your target [[1]].
Thermal conductivity, or lambda value (λ), is a property of a material that indicates its ability to conduct heat. It is measured in W/mK. A lower lambda value means the material is a better insulator. Kingspan products typically have very low lambda values, around 0.022 W/mK [[11]].
Yes, this calculator is suitable for both new builds and renovation projects. You can model existing constructions and calculate the additional insulation thickness needed to achieve a desired U-value for improved energy efficiency.