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Using K-Flex Pipe Insulation to Comply with British Standard 5422 & Part L


K-Flex ST/SK is a Euroclass B s2 d0 closed cell nitrile rubber pipe insulation that is flexible, pre-split and easy to install. It can be used to improve the energy efficiency of heating and hot water pipework and, when used at the correct thickness, it can be used to meet the requirements of BS 5422:2023 and Part L of the Building Regulations.


Nitrile rubber materials such as L'Isolante K-Flex have a high emissivity surface which makes them ideal for condensation control on low temperature pipework. K-Flex is also resistant to mould, fungi and bacteria due to its formulation, making it a great choice for applications requiring a hygienic option.


K-Flex ST/SK is suitable for all applications, both civil and industrial, that require the use of insulation material: refrigeration, air-conditioning, heating and plumbing, tanks, pipe fittings and water ducts.


The calculations provided in this document are correct at the time of calculation. The installer is responsible for correctly installing the material and ensuring that the thicknesses used are correct for the application as intended.

BS 5422:2023 – K-Flex Pipe Insulation Thickness Guide

The following tables provide guidance for using K-Flex ST and K-Flex ST/SK to comply with BS 5422:2023 for domestic heating and hot water applications.

Table 20A – K-Flex ST & K-Flex ST/SK

Pipe SizeThickness
≤ 8.0mm13mm
≤ 10.0mm19mm
≤ 12.0mm19mm
≤ 15.0mm19mm
≤ 22.0mm25mm
≤ 28.0mm25mm
≤ 35.0mm32mm
≤ 42.0mm32mm
≤ 54.0mm (and over)32mm

Table 20B – K-Flex ST & K-Flex ST/SK

Pipe SizeThickness
≤ 8.0mm19mm
≤ 10.0mm25mm
≤ 12.0mm25mm
≤ 15.0mm25mm
≤ 22.0mm32mm
≤ 28.0mm32mm
≤ 35.0mm40mm
≤ 42.0mm40mm
≤ 54.0mm (and over)40mm

K-Flex Pipe Insulation – Euroclass B Pipe Lagging

Material

Elastomeric insulation for all civil and industrial applications.

Thermal Conductivity (EN ISO 8497)

SpecificationValue
Thickness ≤ 25mm0.033 W/mK at 0°C
Thickness > 25mm0.036 W/mK at 0°C
Thickness ≤ 25mm0.037 W/mK at 40°C
Thickness > 25mm0.038 W/mK at 40°C

Temperature Range (EN 14707)

-40°C to +85°C

Fire Performance (EN 13501-1)

Euroclass BL-s2, d0

Application Area

  • Prevents the risk of condensation and improves energy saving
  • Resistant to mould, fungi and bacteria
  • Light and flexible

About Advanced Insulation Materials Ltd


Advanced Insulation Materials Ltd are an independent distributor of thermal insulation materials and ancillaries on Merseyside but covering the whole of the UK. Our ethos is Right Insulation, Right Price, Right Time. Trusted since 2009.


Independent Technical Advice


AIM is an independent thermal insulation distributor that covers the whole of the UK. We work with the leading insulation manufacturers to bring you the very best insulation products, supported by sound technical advice. As one of the few truly independent distributors of thermal pipe insulation, we offer a broad range of options with no product bias.


  • Free delivery on orders over £250 – usually in 2 to 3 days
  • Hundreds of thousands of metres in stock
  • Next day and timed delivery options available
  • In-house technical advice
  • Broad range of accessories
  • Tracked-to-site deliveries



Contact: info@insulationandlagging.co.uk | 01942 295926


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Frequently Asked Questions

What thickness of K-Flex insulation is required for 15mm pipe under BS 5422 Table 20A?
For 15mm pipe, BS 5422 Table 20A requires 19mm K-Flex insulation.
What thickness of K-Flex insulation is required for 15mm pipe under BS 5422 Table 20B?
For 15mm pipe, BS 5422 Table 20B requires 25mm K-Flex insulation.
What thickness of K-Flex insulation is required for 22mm pipe under BS 5422 Table 20A?
For 22mm pipe, BS 5422 Table 20A requires 25mm K-Flex insulation.
What thickness of K-Flex insulation is required for 22mm pipe under BS 5422 Table 20B?
For 22mm pipe, BS 5422 Table 20B requires 32mm K-Flex insulation.
What thickness of K-Flex insulation is required for 28mm pipe under BS 5422 Table 20A?
For 28mm pipe, BS 5422 Table 20A requires 25mm K-Flex insulation.
What thickness of K-Flex insulation is required for 28mm pipe under BS 5422 Table 20B?
For 28mm pipe, BS 5422 Table 20B requires 32mm K-Flex insulation.
What thickness of K-Flex insulation is required for 35mm pipe under BS 5422 Table 20A?
For 35mm pipe, BS 5422 Table 20A requires 32mm K-Flex insulation.
What thickness of K-Flex insulation is required for 35mm pipe under BS 5422 Table 20B?
For 35mm pipe, BS 5422 Table 20B requires 40mm K-Flex insulation.
What thickness of K-Flex insulation is required for 42mm pipe under BS 5422 Table 20A?
For 42mm pipe, BS 5422 Table 20A requires 32mm K-Flex insulation.
What thickness of K-Flex insulation is required for 42mm pipe under BS 5422 Table 20B?
For 42mm pipe, BS 5422 Table 20B requires 40mm K-Flex insulation.
What thickness of K-Flex insulation is required for 54mm pipe under BS 5422 Table 20A?
For 54mm pipe, BS 5422 Table 20A requires 32mm K-Flex insulation.
What thickness of K-Flex insulation is required for 54mm pipe under BS 5422 Table 20B?
For 54mm pipe, BS 5422 Table 20B requires 40mm K-Flex insulation.