NCC 2016 Volume Two
ACT 7.1 Energy Efficiency of Building Alterations

ACT 7.1 Energy Efficiency of Building Alterations



ACT Part 7.1 applies to work in relation to adding to or extending a completed building that can be lawfully occupied or used, where there is not otherwise a requirement to bring into BCA compliance the unaltered part of the building.

Certain substantial alterations or extensions to completed buildings can trigger a requirement under ACT law to bring the unaltered part of the building into BCA compliance. ACT Part 7.1 does not relate to any mandatory requirements to change the otherwise unaltered part of a building, but ACT Part 7.1 can apply to the addition or extension and to unaltered parts where permitted by this part.

The BCA’s provisions generally are intended to apply to construction of entire new buildings and are not inherently intended to apply to altering or extending completed buildings. Nevertheless, ACT legislation requires certain alterations and additions to existing buildings to be done only in a way that produces a building, or affected part, that complies with the BCA.

For the purposes of applying ACT Part 7.1, it is taken as providing additional BCA requirements that only apply in the case of relevant additions and alterations.

ACT 7.1.2(d) and ACT 7.1.2(c) prevent alterations and additions reducing the existing energy efficiency of certain buildings. Nothing in ACT 7.1.2(d) or ACT 7.1.2(c)necessarily requires an energy efficiency rating to demonstrate compliance. Compliance could be demonstrated, for example, through checking that the alteration or addition does not adversely impact on aspects of the existing building that contribute to assessment of its energy efficiency.



The ABCB publishes non-mandatory, non-regulatory information handbooks, about BCA energy efficiency provisions, which clarify that State and Territory legislation applies, or varies the application of, BCA provisions to existing buildings or to alterations or additions to buildings. Some State and Territory legislation permits hypothetical simulation of upgrading elements of existing buildings to facilitate the energy efficiency of new elements in a building extension, without requiring construction to match the simulation. For example, to suppose that glazing units in a dwelling will be upgraded to comparable performance levels of new glazing units in an extension to the dwelling, in order to reduce the burden on the new glazing that arises from having to compensate for the poorer performance of the old glazing. That is not the case in the ACT, and the older glazing’s actual performance must be assessed where applicable, unless a relevant law provides otherwise.

Explanatory information

Explanatory information:

ACT Part 7.1 is intended to help make designs for house extensions comply with the intent of P2.6.1 and P2.6.2. It provides a range of extra options to achieve, compliance, in addition to the BCA’s options. Some of the options cannot be used in combination with others, but others can be used in combination, as explained in the respective clauses. The options are summarised below, and provide for:

  • Allowing the extension to the house to be assessed using house energy rating software, rather than that software only being applicable to the whole of a house (see ACT 7.1.2).
  • Allowing the house extension to meet the elemental provisions (insulation levels, window performance, sealing, etc) of the BCA’s energy efficiency provisions, rather than the BCA’s house energy rating requirements (see ACT 7.1.3).
  • Allowing the effect of certain window treatments such as blinds, curtains, shutters or pelmets to be considered when assessing the thermal performance of existing windows (see ACT 7.1.4(a)).
  • Excluding assessment of thermal performance of an existing window if it is treated with a solar control film (see ACT 7.1.4(d) and the dispensation under the ACT’s Building (General) Regulation 2008, section 29 (1), which allows windows to not comply with the BCA if they have the prescribed film applied).
  • Excluding assessment of thermal performance of an existing window if it is thermally isolated from windows that must be assessed (see ACT 7.1.4(d) in addition to the dispensation under the ACT’s Building (General) Regulation 2008, section 29 (2), which allows windows to not comply with the BCA if they are separated from windows that have to be assessed, by prescribed separating walls, floors, ceilings and doors).
  • Allowing the use of the ABCB 2009 glazing calculator or later to determine window thermal performance compliance where northerly glazing is impractical to provide in a house extension (see ACT 7.1.4(c)).
  • Concessions on use of existing building services, such as reuse of and sealing of ducted air conditioning and reuse of hot water services (see ACT 7.1.6).

This is explained in the following flow chart.