What is a lambda value?
This week, we’re talking about lambda values.
Today we’re launching two new products within our Kooltherm K100 range, each of which have a lambda value of just 0.018 W/m.K across all thicknesses.
When you compare this with the Kooltherm K-range and our Therma range, which achieve between 0.020 – 0.023 W/m.K and 0.022 – 0.026 W/m.K respectively (depending on the product thickness), you can see the difference. But what exactly does it mean, and why is it important?
The term ‘lambda’ is used interchangeably with ‘thermal conductivity’, and measures how well a material conducts heat in units of watts over metres Kelvin (W/m.K). For insulation, the lower the lambda value, the better the thermal performance.
Lambda values are important for completing U-value calculations, which in turn help you to meet Building Regulations.
You might have heard of some other types of lambda too. This BBA guidance document covers everything you need to know on the topic, but we’ve also summarised for you below.
- An aged lambda value predicts the thermal conductivity of insulation over a 25 year period.
- Lambda 90/90 is a statistical analysis to define the thermal conductivity that 90% of insulation production should equal or better, with a 90% confidence limit.
- Declared lambda is lambda 90/90 combined with an additional correction for an aged lambda value.
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