Energy efficiency matters
The objective of energy efficiency provisions in the Building Code of Australia (BCA) is to reduce greenhouse gas emissions, and for a dwelling, this requires compliance with the minimum energy efficiency Performance Requirements that relate to the building envelope and its fixed domestic services.
When applying these provisions for residential dwellings, building surveyors, designers and building industry practitioners should be aware of the following energy efficiency matters:
Separate heating and cooling load limits do not apply in Western Australia
The Building Amendment Regulations (No. 2) 2020 inserted new regulation 15C into Part 2 of the Building Regulations 2012 to dis-apply the heating and cooling load limits that are specified in Parts J0.2 and 188.8.131.52 of the 2019 edition of the BCA..
As part of the overall changes to the energy efficiency provisions of the BCA 2019, the Australian Building Codes Board introduced additional and separate heating and cooling load limits that were intended to enhance the NatHERS (Nationwide House Energy Rating Scheme) compliance pathway for residential buildings.
Following consultation with industry, the State Government agreed that the separate heating and cooling load limits should not be applied to energy assessments in Western Australia. For example; a new house (following a deemed to satisfy solution under the NatHERS compliance pathway) that would have been required to achieve 6 stars and the assigned separate heating and cooling load limits, does not need to comply with the separate heating and cooling load limits.
Use of renewable energy as part of Performance Solution for P2.6.1
It has been brought to Building and Energy’s attention that some practitioners may be attempting to trade the thermal performance of a new house with the adoption of renewable energy sources such as PV panels. They may also be attempting to trade Performance Solution P2.6.2 for services with the requirements in P2.6.1 for buildings.
The performance requirement P2.6.1 sets out the minimum requirements and relates only to facilitating the efficient use of energy for artificial heating and cooling appropriate to various listed matters. Importantly the energy source is not an appropriate matter for the performance requirement P2.6.1. It is therefore inappropriate to take into account a renewable source of energy when determining compliance with P2.6.1.
While the source of energy is a consideration for determining compliance with the performance requirement P2.6.2 for domestic services, the performance requirements P2.6.1 and P2.6.2 are independent from each other and must be evaluated accordingly. It is not appropriate to trade-off between the two requirements.
Use of NatHERS software with the Verification Method V184.108.40.206
Industry is reminded that it is inappropriate to use house energy rating software NatHERS when modelling the heating and cooling loads that are required by the Verification Method V220.127.116.11 – Verification Using a Reference Building.
Further to the DMIRS Industry Bulletin IB 89 from August 2017, amendments to the provisions of V18.104.22.168 in the NCC 2019 act to specifically preclude and discontinue the use of NatHERS software for determining the thermal modelling calculations required by the reference building method.
Despite the ongoing transitional arrangements that allow practitioners in WA to continue using the provisions that are specified in the 2016 edition of the NCC; energy efficiency assessments that are conducted using verification method V22.214.171.124 should be using an appropriate calculation method that is capable of assessing the heating and cooling load by modelling the items listed in the provisions under V126.96.36.199 and be vigilant on the concerns over the erroneous use of NatHERS house energy rating software for this.
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