Part J0 Energy efficiency

Where a solution is proposed to comply with the Deemed-to-Satisfy Provisions, J0.0 clarifies that compliance with Parts J1 to J8 achieves compliance with JP1.

Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2.2(3) and A2.4(3) as applicable. (See commentary on Part A2).

The Deemed-to-Satisfy Provisions described are limited to the most common forms of construction and the simplest forms of buildings. It is expected that the more innovative construction techniques and the more complex buildings will be designed and assessed using a performance approach.

The measures have been developed using a cost-effectiveness model.

A major consideration in developing the measures was the likelihood of a building being heated or cooled by an air-conditioning system, and whether the Deemed-to-Satisfy Provisions should assume this to be the case, or only apply the provisions if a heating or cooling system is installed. It is recognised that most Class 3, 5, 6 and 9 buildings and some Class 7 and 8 buildings are heated or cooled, and this is the basis of the provisions. Consideration was also given to the fact that although the first owner may be prepared to ‘manage’ their building in the appropriate manner, the next owner or tenant may not, and instead may install air-conditioning.

Because of the performance-based structure of the NCC, a Performance Solution may be proposed instead of the Deemed-to-Satisfy Provisions.

J0.1 explains which provisions need to be complied with for—

• a sole-occupancy unit of a Class 2 building or a Class 4 part; and

• all other classifications.

J0.1(a) explains that, for the thermal performance of the building fabric, there are two paths for compliance depending on whether the building contains dwellings (i.e. sole-occupancy units in a Class 2 building or a Class 4 part) or not. For the fabric of dwellings, compliance must be in accordance with J0.2 while for other building classifications, compliance must be in accordance with Parts J1 and J3. For services, all buildings must comply with Parts J5 to J8.

All buildings must comply with J0.1(b) to (e), including sole-occupancy units of a Class 2 building or Class 4 part, due to these matters not being assessed by house energy rating software.

The means of compliance is explained in Figure J0.1.

Figure J0.1 Flow chart of compliance with Section J0

In order to reduce the heating or cooling loads, the fabric of a sole-occupancy unit of a Class 2 building or a Class 4 part must achieve the required house energy rating and the separate heating and cooling load limits. Information about building modelling using house energy rating software is available at www.nathers.gov.au. The applicable heating and cooling load limits are published in the ABCB Standard for NatHERS Heating and Cooling Load Limits, which can be accessed at www.abcb.gov.au.

It must also comply with a few general Deemed-to-Satisfy Provisions relating to the insulation standard, installation of insulation, thermal breaks, sealing, etc.

The measures for a sole-occupancy unit of a Class 2 building or a Class 4 part of a building are similar to those adopted for Class 1 buildings in BCA Volume Two - Housing Provisions. There are several reasons for this, including:

• Many Class 2 and 4 buildings are very similar in thermal performance to Class 1 buildings.

• Being dwellings, there are similarities in their use with high occupancy at night.

• Having all types of dwellings achieving comparable performance provides a consistent approach.

Importantly, as per Class 1 buildings, a sole-occupancy unit of a Class 2 building and a Class 4 part of a building must satisfy both the required star rating and the corresponding heating and cooling load limits. The star rating is based on the combined heating and cooling load of the dwelling, whereas compliance with the heating and cooling load limits is dependent on the separate heating and cooling loads of the dwelling.

Further information about house energy rating and heating and cooling load limits can be obtained on the website of the Nationwide House Energy Rating Scheme.

A ceiling fan may be required to provide high air movement as part of a house energy rating software solution and two sizes of fans are described in terms of their diameter and the floor area they serve.