The National Construction Code (NCC) is a performance-based code which sets the ‘deemed to satisfy’ (DTS) requirements for the construction of all buildings and is given legal effect by relevant legislation in each State and Territory.
The legislation consists of an Act of Parliament which provides the States and Territories with the powers to regulate building, plumbing and drainage works within their jurisdiction.
Volume two of the NCC sets out the requirements for residential and non-habitable buildings and structures. (NCC | Australian Building Codes Board, 2020).
In 2003 the NCC introduced sections on Energy Efficiency for houses and residential construction into Volume Two in line with adopted strategies to improve energy efficiency in buildings by Commonwealth, State and Territory legislative bodies.
In 2009, the Council of Australian Governments (COAG) asked the Australian Building Codes Board (ABCB) to increase the requirements of all building for the NCC 2010 version, including the requirement for housing to be 6 star or equivalent rating.
Between 2010 and 2019 only minor updates were made to the energy efficiency requirements within the NCC.
In 2015 COAG released its National Energy Productivity Plan (NEPP) which found that the current NCC could achieve energy savings of up to 53% in commercial buildings but only 18% for residential buildings and so, requested the ABCB update the energy provisions in NCC Volume One and Two. (Energy Efficiency NCC Volume 2 Handbook, 2019)
The requirements for compliance for energy efficiency have been updated significantly for both Class 1 and Class 2 buildings with the means for improved interpretation and application of the provisions. These changes include;
· Separate heating and cooling load limits have now been included which results in buildings taking the deemed to satisfy approach will need to meet the six-star standard or equivalent. (HIA, 2020). This supplements the National House Energy Rating Scheme (NatHERS) star rating system.
· Reinforcing the reference building Verification Method.
· Introducing a Verification Method for building envelope sealing, and
· Clarifying building sealing requirements under the Deemed to Satisfy (DTS) method. (Energy Efficiency NCC Volume 2 Handbook, 2019)
In Western Australia and other areas which commonly use cavity masonry construction, changes to the Reference Building Verification Method, which can be used as part of complying with energy efficiency requirements will impact the design of houses. (HIA, 2020).
The Reference Building Verification method involves modelling the thermal performance of the proposed building against a reference model heating and cooling loads. When both the proposed and reference building have been modelled, the heating and cooling loads are compared. If the proposed buildings loads are equal to or less than the reference building heating and cooling loads, then the building has achieved deemed to satisfy compliance. If not, then adjustments to the design are to be made, which may be increased insulation, solar shading, a change to a building fabric material, less glazing or more efficient building services.
Under NCC 2019 previously accredited software provided by NatHERS is no longer permitted to undertake the reference building verification modelling. (Australian Building Codes Board, 2021)
To summarise, the changes to the 2019 NCC Energy Efficiency requirements mean that houses and residential buildings need to comply both from a heating and cooling load perspective, meaning the installed systems must be energy efficient both in summer and winter and, along with, improved building fabric performance which results in less leakage and improved insulation which in turn means less heat loss in winter and heat gain in summer, as well as causing less condensation.
As six-star standard has been regarded as the base norm for residential construction for some time, most house designs already meet or exceed this standard. However, the changes in NCC 2019 mandate this standard for all houses and some designs will need to be updated to comply.
As well as more efficient buildings the benefits also include greater comfort and economic benefits to the inhabitants.
Study is well underway for future and further changes to energy efficiency provisions for NCC 2022 with an emphasis on residential buildings. (Energy efficiency - NCC 2022 and beyond scoping study - Australian Building Codes Board - Citizen Space, 2021)
References
NCC.abcb.gov.au. 2020. NCC | Australian Building Codes Board. [online] Available at: <https://ncc.abcb.gov.au/> [Accessed 20 March 2021]. HIA, 2020. NCC 2019 Changes. 2020 Housing Industry Association Limited.
Australian Building Codes Board, 2021. Reference Building Verification Method. [video] Available at: <https://www.youtube.com/watch?v=vvwtzd3pYV8> [Accessed 28 March 2021].
2019. Energy Efficiency NCC Volume 2 Handbook. 4th ed. Canberra: Australian Building Codes Board.