Big changes afoot

The 2019 edition of the NCC contains a number of significant changes affecting all classes of buildings, including: houses, apartment buildings less than four storeys (low-rise), and apartment buildings above four storeys but under 25 metres (mid-rise).

The extent of the impact for residential buildings is difficult to determine in terms of a dollar amount, but it will mean that many house and apartment designs will require some amendments. Some building products may even require adjustment – or worse, may no longer be useable on certain building types.

The major changes to affect housing include:

• introduction of condensation management provisions, including the use of vapour permeable membranes in certain climate zones and external ducting of exhaust under certain circumstances;
• introduction of separate heating and cooling loads for NatHERS energy efficiency star ratings;
• revision of the existing reference building verification method (V2.6.2.2), including clarification of the software tools that can and cannot be used to undertake modelling for this method; and
• more prescriptive building sealing requirements and inclusion of a verification method (optional) for building sealing, that is the use of the ‘blower door’ test.

Individually, these changes may not seem substantial, but the cumulative effect may mean that many house designs will require some change.

In particular, the inclusion of separate heating and cooling loads will mean that buildings will need to meet the six-star standard (or equivalent) as well as the prescribed heating and cooling load limits caps. Conservative estimates suggest that this will impact 10 per cent of house designs in both cool and warm climates – but HIA believes that this number is likely to be much higher.

The inclusion of the condensation management provisions is in response to growing calls for this issue to be addressed, particularly for houses in Australia’s colder climates. The provisions are intended to be the first of a suite of changes to come in future editions of the code.

It should be noted that the provisions include measures to assist in ‘managing or minimising’ the impact of condensation in buildings, which acknowledges that the issue with condensation is as much about how people use the building as it is about designs and materials used in the construction.

The changes to the Reference Building Verification Method will impact house designs in Western Australia, in particular because this has been a common energy efficiency compliance path used due to the predominant use of cavity masonry construction.

On a positive note, the NCC will reintroduce into the code Deemed-to-Satisfy Provisions for masonry veneer construction and improvements to many other parts of Volume Two, resulting from the ABCB's Acceptable Construction Practice Review project.

HIA welcomes this approach to developing NCC provisions; for many years industry has sought the inclusion of content back into the NCC itself, rather than wholly relying on referenced standards.

Additionally, the new edition will incorporate revised and enhanced BCA product evidentiary requirements for determining a product’s fitness for purpose. This also includes the updating of the ABCB evidence of suitability handbook.

The major changes that will affect low- to mid-rise Class 2 buildings include:

• mandatory sprinkler protection for buildings four storeys and above (with offsets);
• the condensation and energy efficiency changes, mentioned above;
• energy efficiency stringency increases for commercial buildings which will affect common areas, shared services of apartments and mixed use buildings (apartments with ground floor cafés and shops).

The energy efficiency stringency increases for commercial buildings will impact those working on mixed use apartment buildings and commercial buildings and product suppliers to those buildings.

Other changes include retaining the bonded laminate materials clause from C1.9(e) – (formerly C1.12) – and permitting certain types of sarking materials that meet prescribed criteria to be used in external walls required to be non-combustible.

Yes, referenced standards have certainly not been missed. In addition to the NCC changes, an unprecedented amount of standards have been revised and updated.

Some of the affected standards more relevant to the residential building industry include:

• AS 3959 Construction in bushfire prone areas
• AS 1562.1 Metal roof and wall cladding
• AS 2050 Installation of roof tiles
• AS 4200 Parts 1 and 2 – Pliable membranes
• AS 3700 Masonry structures
• AS 4859 Insulation in buildings
• AS 5146 Autoclaved aerated panels
• AS 3500.3 Plumbing and drainage – stormwater.

In addition to being aware of the changes within the NCC itself, it’s equally important to ensure you are aware of the changes to the Australian Standards called up by the NCC, since they can significantly impact designs and installations.

In most states and territories the changes will take effect from 1 May 2019. However, some will be subject to a 12 month transition period, such as changes to the energy efficiency provisions.

HIA will be running a series of seminars in all capital cities from 19 March through to 27 April 2019 with ABCB participating at the Canberra event. These seminars will include a ‘deep dive’ analysis into the major changes (and more) affecting houses and low- to mid-rise residential buildings.

The views expressed in this report are those of the authors only and should not be construed in any way as having been endorsed, or as representing the views of the ABCB.