J5.6 Ductwork sealing

[Air-conditioning ductwork has joints, and unless sealed these joints will allow heated or cooled air to escape. To limit this heat loss or gain, ductwork must be sealed with adhesives, mastics, sealants, gaskets or the like in accordance with AS 4254 Parts 1 and 2 for the static pressure in the system. AS 4254 is the standard covering ductwork for air-handling systems in buildings. These requirements do not apply to ventilation ductwork where the air is not heated or cooled.

The requirements only apply to duct systems with a capacity of 3000 L/s or greater. The requirements do not apply to ductwork in the space being conditioned or the last room served by the system, as the air is intended for that space anyway.

The duct leakage tests of clause 2.2.4 of AS 4254.2 are included in this requirement. The key purpose of this is not so much to deal with minor leakage but to ensure that there are no major leaks such as uncapped spigots and similar in the system. Construction errors of this nature can cause leakage rates in excess of 20% in some systems, severely compromising system performance.]