Duct Air Leakage
Why is ventilation compliance not being met across the industry, and what is contributing to this non-compliance?
It is Not a matter of compliance. The right question is more like, “Why the systems are not performing as designed?” The NCC does not demand any proof of performance by empirical test (the test is prescribed in AS4254.2 2012 but that section of AS is subsequently excluded from the NCC requirements in 2015 – in the explanatory note, so it is technically a grey area as the explanatory note is NOT enforceable). Traditionally, the compliance issue has always been dault with using deem to satisfied methods. As long as the duct manufacturers and installers only have to follow the prescribed methods and procedures for compliance. In the past, only special buildings may prescribe pressure testing of ductworks by the mechanical consultants.
Is a lack of compliance checking contributing to this (out of sight, out of mind)?
It is more like the contractor did not receive feedback on non-optimum practices, therefore unknowing carry on the poor practices. The other reason is that the industry focus on the volume of air being delivered at various outlets as a key performance indicator for HVAC ducts. As long as the HVAC contractor meets the air delivery specified, it’s a job well done. Regardless of the level of leakage. Sometimes the slight oversized air handler ( safety margin) also reduces the incentive to improve duct sealing as the installers know there is going to be enough slack.
What do the NCC and/or standards require to achieve compliance? How is duct sealing measured? NCC requires testing a percentage of ductwork for compliance. Pressure Testing is used. Raising the duct pressure with a calibrated fan/ pitot tube.
If duct airtightness is to be taken seriously, Aeroseal is a no-brainer...