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The standard for pipe insulation

Sunday 8 March 2026

Ensuring a continuous and effective layer of insulation across all building services is crucial to limit heat transfer and support system performance. For specifiers and contractors, the key reference point when selecting insulation products and thicknesses for a system is BS 5422: 2023.

BS 5422

Along with best practice guidance around insulating building services (such as managing condensation and fire risk), BS 5422 contains a range of tables with minimum or indicative insulation thicknesses for pipes, tanks, vessels, ductwork and other equipment operating at temperatures between -40^oC to +700^oC. The tables are designed to cover a wide range of common systems considering factors such as operating temperatures, ambient air humidity and the dimensions, location and orientation of services.

Kingspan Kooltherm Pipe Insulation can meet the minimum and enhanced values in BS 5422: 2023 with slim thicknesses of pipe insulation.

In the latest version of the standard, a specific district heating table is included based upon 55 °C flow temperatures which should be read together with the guidance in CIBSE CP1 – Heat Network Code of Practice.

A number of tables with enhanced insulation thicknesses are also provided. These values have been taken from the legacy Energy Technology List and can support project teams working to achieve net zero operational emissions. In addition, the standard implies that, in cases where specific instructions from the specifier are absent, contractors should default to these enhanced values.

The thicknesses of insulation required vary depending on the lambda value (thermal conductivity) of the insulation. The lower this value is, the more effective the insulation material will be at preventing heat transfer. This can mean a slimmer layer of insulation can be specified than would be possible with a worse performing material, whilst still maintaining the required thermal performance.

Kingspan Kooltherm Pipe Insulation features a phenolic insulation core with thermal conductivities as low as 0.025 W/mK.

The lambda value of common building service insulation products can vary considerably. For example, phenolic pipe insulation products can achieve aged thermal conductivities as low as 0.025 W/mK. By contrast, mineral fibre lagging typically achieves thermal conductivities of 0.033 W/mK or worse. This can have implications for system design and installation, affecting how closely pipework can be fitted together and consequently the dimensions of service spaces.

All manufacturers should provide clear information about the thermal conductivity of their products. The specific value for an application will vary depending on the mean temperature of the insulation for the given application.

Getting up to speed

To help specifiers fully understand the requirements under BS 5422, Kingspan Technical Insulation offer a free, CIBSE approved CPD: A Guide to Thermal Insulation & Standards. This 45 min seminar can be delivered in person or virtually and covers a range of key standards and installation guidance.