VENTILATION
DUCTWORK
“For years ductwork specialists have argued that some ductwork gauges were over-specified and, therefore, thicker than they needed to be in many applications. The new DW/144 addresses this and supports the case for thinner gauges.”
behalf of the BESA concerning panel/flange deflection, duct gauges and ductwork strength and air leakage testing For years ductwork specialists have argued that some ductwork gauges were over-specified and, therefore, thicker than they needed to be in many applications. The new DW/144 addresses this and supports the case for thinner gauges with in-depth test data and validation. The new specification also recommends a reduction in the number of gauge, flange/stiffener manufactured assemblies; dispensing with the need to treat spot welds; a reduction in coatings thickness/protective finishes; and provides further clarification of standard duct sizes. The 200-page document, which has been aligned to all current British, European and international standards, covers ductwork application, materials, classification and air leakage rates. It defines the technical information to be provided by system designers to ductwork contractors; and looks in detail at rectangular, circular, and flat oval ductwork. A number of significant legislative changes have taken place since the first edition was published including the appearance of the Construction Products Regulation, CE Marking and the Construction (Design and Management) Regulations, along with other measures designed to enhance environmental management and health and safety. This has led to major changes in the Building Regulations, requiring clarification of the classes of ductwork to be tested, along with the re-introduction of high-pressure Class D to conform to European practice.
Expanded The content of DW/144 has been expanded to give more detail on hangers and supports, smoke and fire dampers, external ductwork, internal duct linings, thermal insulation, air terminal units, connections to builders work, as well as re-affirming the importance of the provision of a clean, dry environment into which sheet metal ductwork should be installed. It also contains a large number of reference tables. Special emphasis has also been placed on the inclusion of access panels in ductwork installations to make it easier for systems to be properly cleaned and maintained in situ. This follows in-depth consultations with the BESA Ventilation Hygiene group, which produces the sector’s main source of ductwork cleaning guidance (TR/19), and leads the sector’s efforts to reduce fire risks and hazards to human health associated with improperly cleaned and maintained ductwork systems. Another major consideration for the authors of the revised specification was that it should continue to offer realistic benchmarks to which all individuals and organisations are able to perform. Therefore, DW/144 now incorporates messages from the BESA publication, Acceptance Scheme for New Products: Rectangular Cross Joint Classification (DW/TM1), which establishes performance ratings for both air leakage and deflection for cross-joints. In order to validate the parameters set out in DW/144, the Association has undertaken extensive testing against recently-introduced CEN requirements to measure panel/flange deflection and air leakage testing. Testing has also been undertaken to determine the lifespan of untreated spot welds over a 30-year period. During the drafting process, the Committee consulted widely with individuals and organisations throughout the building engineering services and construction industry to ensure this revision clearly demonstrates the high level of professionalism which exists within the ductwork community.
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