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Insulation of flues and chimneys needs to match the increasing air tightness of buildingsJanuary 2021

Legislation and market demand for low carbon solutions are driving the adoption of higher levels of insulation in new build properties and an increasing number of passive house projects.

These upgrades also mean that related services must change to accommodate these increases.  In the case of flues and chimneys, heat that would otherwise be lost through the building structure is now retained.  Insulated flues must now demonstrate that their own insulation is sufficient, to ensure there are not dangerous levels of local overheating, that could damage the building structure, or lead to fires.

The recently released EN 1443:2019 lays out a series of standard structure types which cover the European market, with varying levels of insulation applied to walls and ceiling in conjunction with the floor penetration and enclosure variations.   The standard also specifies the U & R values required for the test structures based on National building regulations. Manufacturers can then select and test in accordance with classes relevant to their markets and local methods of construction and regulation.

Most existing housing stock in the UK will be best represented by structure type “b”, with U value represented by a 100 mm wall and floor thickness.  For new build, the U value is represented by a 200 mm wall and roof thickness, close to type “c”.  For passive house, the U value is represented by test structure “e” which increases the wall and roof thickness to 400mm.

An additional designation letter will be added to the product designation for the type of test structure used during the testing, as shown in the example below. The product designation includes, temperature class, pressure class, corrosion resistance class and sootfire resistance class with distance to combustible material where appropriate, and the type of test structure:

i.e. ENxxxxx – T400 – N1 – D – 3 – G – 50 – c

While EN 1443:2019 is now published, the related harmonised product standards for different chimney types are still being finalised. This means that testing with the new structure types is not yet a requirement for CE marking (or the UKCA mark).

However, some manufacturers are already looking to carry out testing on their existing products to the enhanced requirements and listing the data on a voluntary basis.

As an ISO 9001 accredited laboratory, BSRIA has expertise and a purpose-built facility which has recently been upgraded for comprehensive testing of chimneys.  We can also carry out development testing for our clients, on a range of product types

  • Metal system chimneys
  • Metal flue liners
  • Clay/Ceramic liners
  • Concrete flue liner/blocks
  • Plastic flue liners

BSRIA has now added to its existing chimney testing capability, to ensure that the new testing requirements can be met in a timely fashion, allowing manufacturers to be ready for the anticipated changes.

Please contact us now for further information:


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