---
title: Learn how to measure thermal insulation performance
description: Whether you are an architect, contractor or developer, you may need to compare the thermal performance of different materials for an upcoming construction project.
---

[Synthesia Technology- Polyurethane Systems](https://blog.synthesia.com/en)

# [Learn how to measure thermal insulation performance](https://blog.synthesia.com/en/learn-how-to-measure-thermal-insulation-performance)

 Written by [Synthesia Technology](https://blog.synthesia.com/en/author/synthesia-technology) | 08 September 2026

Whether you are an architect, contractor or developer, you may need to compare the thermal performance of different materials for an upcoming construction project. Thermal performance is a key element in determining the energy **efficiency of buildings. **

## **Values for measuring thermal performance**

Although several values are used to measure different aspects of the thermal performance of materials, such as C-value (thermal conductance) and K-value (heat transfer between the outside and inside of a building), the insulation performance of a product is typically measured using three thermal values: the **coefficient of thermal conductivity (λ), thermal resistance (R) and thermal transmittance (U).**

## What is the thermal conductivity coefficient (λ) value?

The **coefficient of thermal conductivity (λ)** is the intrinsic property of materials and is related to the amount of heat that is transmitted between the two faces of a flat surface of a material, the lower this value the better thermal insulator the material is. It is expressed in units of W/(mK).

## What is the thermal resistance (R) value?

The **R-value** indicates the **thermal resistance of a material** or its ability to resist heat flow. Expressed as m²K/W, the R-value depends on the thickness of the material used, unlike the lambda value. The **higher the R-value of a product, the higher the thermal resistance** and therefore the more energy savings it provides.

## What is the thermal transmittance (U) value?

Often mistakenly considered the inverse of the **R-value**, the U-value actually **measures thermal transmittance**, or how fast heat moves through a given product, whether it is composed of a single material or multiple materials. Like the R-value, the U-value of a product also depends on its thickness, although conversely, lower U-values indicate better insulation.

**To summarise:**

**d = material thickness (m)**

**(λ) : thermal conductivity - (W/mK) - The lower the value, the better the insulation performance**

**R = d/λ : thermal resistance - (m2K/W) - The higher the value, the better the insulation performance**

**U = 1/ summation R : heat loss value - (W/m2K) - The lower the value, the better the insulation performance **

## **Polyurethane as insulation for energy-efficient buildings**

As the demand for energy-efficient buildings continues to grow, building professionals are increasingly turning to smarter[**insulation solutions based on hybrid technologies. **](https://blog.synthesia.com/en/benefits-continuous-insulation)

[**Polyurethane foam**](https://www.synthesia.com/en/pu-systems/polyurethane-spray/), which is generally considered one of the best products for insulation, has a lambda value that can range from 0.018 for panels to 0.042 for low-density open-cell. As insulation technologies continue to evolve, we can expect to see even greater improvements in the thermal values of products, resulting in even more impressive energy efficient buildings.

 

[View full post](https://blog.synthesia.com/en/learn-how-to-measure-thermal-insulation-performance)

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