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B&ES updates DW/144

Ductwork DW144UK: The Building & Engineering Services Association (B&ES) has published important updates to its ductwork specifications DW/144 and DW/143.

DW/144: Specification for Sheet Metal Ductwork, is a comprehensive reference work recognised as the standard specification for ductwork manufacture and installation. DW/143: Guide to Good Practice – Ductwork Air Leakage Testing, provides a concise practical guide to leakage testing and ductwork classification.

First published in 1963, DW/144 has since gained national and international recognition as the standard against which the quality of ductwork manufacture and installation should be measured. The newly-released second edition has been aligned to all current BS, BS EN ISO and other standards and regulations and takes account of latest developments in technology and working practices.

“A key element in reviewing DW/144 was to ensure that the specification continues to offer realistic benchmarks,” explained Peter Rogers, chairman of B&ES Ductwork Group Technical Committee.

“During the drafting process, the technical committee consulted widely with individuals and organisations throughout the building and engineering services and construction industry to ensure that the new specification fully reflects current, state-of-the-art technical expertise and industry best practice.”

DW/144 defines specifications for sheet metal ductwork for low, medium and high pressure/velocity air systems. The publication’s 200 pages cover ductwork application, materials, classification and air leakage; define the technical information to be provided by system designers to ductwork contractors; and look in detail at rectangular, circular, and flat oval ductwork. Content has been expanded on hangers and supports, smoke and fire dampers, external ductwork, internal duct linings, thermal insulation, air terminal units, fire-resisting ductwork, and ductwork for swimming pools, with many clear reference tables.

DW/143 has also been brought fully up-to-date, with clear explanations of the classes of ductwork that must be tested under regulations, acknowledging the re-introduction of high-pressure Class D ductwork to conform to European practice. Leakage testing of high-pressure ductwork is mandatory in DW/144, with testing of ductwork designed to operate at low and medium pressures not mandatory and required only when stipulated in individual job specifications.

In his foreword to DW/143, Peter Rogers makes a sobering observation: “Ductwork contractors faced with a job calling for leakage testing should take this requirement very seriously and satisfy themselves as the job progresses that the required leakage rates are within the limits set by the system designer or the client. The cost of making good an installation that has been found on completion to have failed in this respect can be very expensive.”

The first section of DW/143 deals with the practical considerations of leakage testing with useful hints and tips and an example of a completed test sheet. The second section of this easy-to-read 18-page guide covers ductwork classification and air leakage.

Both DW/144 and DW/143 have been called up in the UK Building Regulations Approved Documents L2A and L2B which deal with the conservation of fuel and power in buildings other than dwellings and which set out the requirements for the testing of ductwork.

For more information or to purchase a copy of DW/144 or DW/143 visit

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