Residential buildings

Building code changes

Increased energy efficiency measures are on the agenda for the Building Code of Australia, including changes for residential buildings.


Simon Croft

The Australian Building Codes Board (ABCB) has recently released the proposed changes to the 2019 edition of the Building Code of Australia (BCA) for both Volume 1 and 2.

The draft changes came out for comment in March this year and a large number relate to energy efficiency, along with more general changes to each of the parts of Volume 2 for housing.

The substantive changes to the code are proposed for the energy provisions. These changes will affect both residential buildings and commercial buildings, with commercial buildings subject to significant stringency increases beyond the current requirements.

For residential buildings, the changes are not as significant, but there are numerous changes that will collectively impact house designs in many parts of Australia.

By way of background on the proposed changes, in 2015 the Council of Australian Governments (COAG) developed a National Energy Productivity Plan (NEPP), which contained a package of measures aiming to improve Australia’s energy productivity by 40 per cent by 2030.

Measure 31 of the NEPP forecast productivity and emission reduction benefits from revising the National Construction Code’s (NCC) energy efficiency provisions for residential and commercial buildings.

However, in developing this measure, it was recognised that there is a need to gather more evidence on the effectiveness of the existing provisions, particularly for residential buildings.

On this basis, for NCC 2019 the ABCB was instructed to focus on increasing the stringency of the energy efficiency provisions for commercial buildings.

For residential buildings, the proposed changes for NCC 2019 involve improved interpretation and compliance with the current provisions, in preparation for possible increased stringency in the future.

Residential buildings
Changes impacting house designs in many parts of Australia will affect residential buildings
Commercial buildings will be subject to significant stringency increases beyond the current requirements

Commercial buildings

The draft of BCA Volume 1 Section J contains proposals to increase the stringency of the energy efficiency provisions for commercial buildings. Commercial buildings in this respect include Class 3 buildings (hotels and motels) and Class 5 to 9 buildings. The changes also affect the common areas of Class 2 buildings (apartments and units).

The amendment includes:

• changes to the energy efficiency performance requirement by attempting to prescribe a ‘quantified’ level of performance for buildings with a conditioned space
• adding new optional means of satisfying the performance requirement JP1 by using NABERS Energy or Green Star ratings. These will be listed as verification methods allowing their use as part of a performance solution
• introducing an optional means of meeting building envelope sealing requirements by using the ‘blower door test method’.

A range of other changes have also been made to the Deemed-to-Satisfy provisions, including the provisions for fabric and glazing, sealing, air-conditioning and lighting.

The impact these changes are expected to have on the commercial building sector and those supplying products for commercial buildings is extremely hard to gauge. The current Section J provisions are complex and the proposed changes would make them even more complex. HIA’s discussions with members suggest the changes will have a significant impact.

Residential buildings

Residential buildings are Class 1 buildings, the sole-occupancy units of Class 2 buildings and a Class 4 part of a building. The proposed changes have focused on enhancements to the current energy provisions and improving interpretation and compliance.

The proposed changes include:

• introducing separate heating and cooling load limits to supplement the Nationwide House Energy Rating Scheme (NatHERS) star rating requirements, to improve the performance of dwellings throughout the year, particularly in times of extreme heat or cold
• tightening the language for the reference building verification method and including more prescriptive modelling parameters
• including the blower door test method for building sealing via an optional verification method
• changes to the building sealing prescriptive provisions.

A range of other minor changes have also been made to Part 3.12 to improve the existing energy efficiency provisions.

Both BCA Volumes 1 and 2 have proposed the inclusion of a number of new measures to minimise the potential impact of condensation in buildings. This includes the use of vapour permeable membranes in certain climate zones, roof space ventilation and external ducting of exhaust fans and range hoods, under certain circumstances.

While these changes may not seem to be substantive individually, collectively they will impact the residential building industry. In fact the changes may mean a number of current building designs require changes or will no longer be accepted.

HIA participates on the ABCB’s energy efficiency residential working group that was consulted on these changes. As part of this process HIA raised the practical application of a number of the changes and the potential implications they may have on different building typologies across the country.

Next steps

The proposed changes were released for public comment throughout February and March and comments closed mid-April. Going forward the ABCB and its technical advisory committees will consider the public comments and endorse a final version of BCA 2019. This will be released as a preview early next year, prior to taking effect in May 2019, subject to any state and territory transitional periods.

HIA will provide further advice to members on the approved changes when the final version is released. Members are encouraged to review the public comment draft on the ABCB website to prepare for any changes your business may need to make to house designs or approval processes.

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