Recently it became clear that an understanding of the intent and purpose of a clause, or the “functional statement” in the NCC and an Australian Standard is very important to achieve the correct application.

The good old five, six or even seven W’s – who, what, where, when, why, how, and how much – which seem to have started out in in journalism, research, and police investigations, can be applied in the use of performance solutions. In the application of a clause from an Australian Standard, it is important to look at these questions and be able to answer them. Post-examination of the process and thoughts used to resolve a recent application of clause 2.5.1 in AS/NZS4254, showed the six W’s followed as:

  • Who is the target audience of the clause?
  • What is the key performance requirement that should be meet?
  • Where is the clause to be applied?
  • When is the performance requirement important – under what conditions?
  • Why is the performance requirement important?
  • How is covered in the what, when and where (so we shall leave this out)
  • How much does it cost to meet this requirement?

It is best to use an example here to demonstrate how this is applied, so I shall give some background without getting into specifics of the actual project, for confidentiality reasons. The NCC references AS/NZS4254.1-2012 as an applicable standard for the installation of flexible ductwork within buildings. The specific clause of interest is Clause 2.5.1 which states:

“In buildings of Class 4 to 9 inclusive, as defined in the National Construction Code, flexible duct shall only be used for final run-out to air terminal devices and be single lengths of 6m maximum. No intermediate joints permitted.”

Some installed flexible duct was deemed to not meet the requirements of this clause. We examined the clause and had some difficulty in understanding the intent and reason for why our situation did not comply. I shall run through the W’s and cover the easy ones first, as there is some detail needed to cover the remaining.

  • Who – the installer of the flexible duct
  • Where – the flexible duct connecting to the terminal air supply devices
  • How much – this depends on how the clause is applied, but it can be very expensive

The what, when and why are tied up together and, as we found out, it is not a simple matter of just reading the clause and applying it directly.

An installation existed where a length of flexible duct was joined to another length via a length of hard metal duct, but was under the limit of six metres. Why is there a requirement for it to be a single piece of duct, what is the intent, and under what conditions does this impact on the intent of the NCC?

We considered the key requirements of the NCC for safety, health, amenity and sustainability in the design and construction and could not understand the intent of this clause. All duct within a building has to meet fire safety requirements and the product used was meeting those requirements irrespective of it being one or two pieces. Similarly, health, amenity and sustainability were not affected by having the duct arrangement as installed.

Therefore to answer the what, when and why, we investigated further and spoke to the people involved with the development of AS/NZS4254.1-2012. Understanding the intent, answered the three remaining questions for us, and the answers were much simpler than we expected. As it turned out, the installation was meeting the intent of the clause. The intent of clause 2.5.1 when referring to a single piece of duct, was to stop installers from joining many small pieces of flexible duct offcuts to make a six-metre length.

The situation resulted in no change to the ‘as installed’ flexible duct, and a happy client. A major cost to the project and potential delay to the construction schedule was avoided by answering the six W’s.