A BASIX assessment for a new home is not approached in exactly the same way as an assessment for an alteration, extension or second-storey addition. Both project types may need to demonstrate residential water, energy and thermal performance, but the starting point and assessment boundary can be different.

A new home can generally be assessed as one complete proposed dwelling. An alteration or addition begins with an existing building and requires the plans and assessment to distinguish between what is retained, removed, changed and newly constructed.

Understanding that distinction early helps architects, designers, builders and homeowners prepare the right information and avoid conflicting assumptions between the BASIX Certificate and the approval drawings. For a broader overview of the framework, see What Is BASIX? →

Do Relocatable and Transportable Homes Need BASIX in NSW?

Whether a transportable, prefabricated or modular home needs a BASIX Certificate in New South Wales depends on how the dwelling is legally classified and how it will be installed—not simply on the name used by the supplier.

Under current NSW planning guidance, a dwelling that qualifies as a relocatable home is treated differently from a flat-pack kit home erected as a building. A relocatable home generally does not require a BASIX Certificate, while a flat-pack dwelling requiring a development application or complying development certificate generally does.

The approval pathway still needs to be confirmed with the relevant council or certifier before documentation is prepared. A project can require council approval even where BASIX does not apply.

Do Green Roofs Help with BASIX in NSW?

Green roofs are increasingly considered in sustainable residential and mixed-use developments across New South Wales. They can provide valuable environmental and design benefits, but their relationship with a BASIX assessment is often misunderstood.

A green roof does not automatically earn a BASIX credit or replace the roof, insulation, glazing and building-services commitments needed to satisfy the assessment. Its influence depends on which parts of the system can be represented through the applicable BASIX and thermal performance methodology.

Does AAC Improve BASIX and NatHERS Performance?

Autoclaved Aerated Concrete, commonly known as AAC, is widely used in Australian residential construction as wall panels, blocks and lightweight masonry cladding systems. Its air-filled structure can provide useful thermal resistance while remaining substantially lighter than conventional concrete.

AAC can form part of a well-performing BASIX and NatHERS design, but the material does not automatically produce a higher energy rating. The result depends on the complete wall construction, including the AAC thickness, frame type, insulation, cavities, internal lining, external finish and any thermal bridging through the assembly.