U-Value & R-Value Calculation Guide

U-value (also known as thermal transmittance) measures how much heat is lost through a building element such as a wall, roof or floor. It is expressed in units of W/m²K (Watts per square metre per Kelvin) — the lower the U-value, the better the element resists heat loss and the more thermally efficient the building will be.

U-values take into account all layers in a construction, including insulation, membranes, air gaps and surfaces. Because of this, a U-value gives a more complete picture of thermal performance than a simple R-value for an individual material.

Accurate U-value calculation is crucial for:

• compliance with building regulations

• optimising energy efficiency

• minimising heat loss and reducing energy bills
  especially in roofs, walls and floors.

Using an online calculator, such as the official SuperFOIL U-Value Calculator, helps you quickly assess the thermal performance of your specific build-up without needing manual calculations.

R-values are another common way to represent insulation performance. An R-value (Resistance value) measures the thermal resistance delivered by a specific thickness of material. The higher the R-value, the better the thermal performance.

While R-values are useful for comparing individual materials, U-values reflect the performance of the complete construction build-up, which is essential for regulatory compliance.

Open Official U-Value Calculator