What 7-star BASIX means for your new home

If you are planning a new home or a dual occupancy in NSW, the energy and thermal requirements are no longer an afterthought. They shape the design from the start, including window sizes and positions, insulation, and the choice of materials.

What changed

The NSW Government's BASIX (Building Sustainability Index) standards were increased for new residential development from 1 October 2023. According to the NSW Department of Planning:

• The thermal performance standard rose from an average of 5.5 to 6 stars to 7 stars on the Nationwide House Energy Rating Scheme (NatHERS).
• Greenhouse gas emissions are reduced by 7 to 11 per cent, depending on location and the type of development.
• A materials index was introduced to measure embodied emissions, meaning the greenhouse gases generated in producing and transporting construction materials.
• The higher standards do not apply to homes in climate zones 9, 10 and 11, or to apartment buildings up to five storeys.

Homebuyers who had signed a building contract before 1 October 2023 were given a time-limited transition period. The Department indicated it would end by 30 September 2024, so a new project today should expect to be assessed against the current standards.

What a NatHERS star rating measures

NatHERS rates the thermal performance of the building's shell, which is how much heating and cooling energy a home needs to stay comfortable. A higher star rating means a home needs less energy to stay at a comfortable temperature. It is a modelled result based on the design, so it depends on decisions made on paper, before construction starts.

Where the biggest decisions are

Every home is different, but the same design factors tend to matter most:

• Orientation and layout. Living areas that take advantage of northern sun (in the southern hemisphere), with well-shaded west-facing glass.
• Windows and glazing. The size, position and performance of glazing, and whether it is shaded by eaves or screens.
• Insulation. Ceiling, walls and floors, and, just as important, installing it properly without gaps or compression.
• Air sealing. Reducing unwanted air leaks so that the thermal envelope actually performs the way it was modelled.
• Materials. Thermal mass, cladding and roof colour, and now the materials index.

What this means for owners and developers

• Budget for it early. Meeting the standard can affect the design, the glazing and the cost. It is far easier and cheaper to plan for it at concept stage than to redesign later.
• Get the assessment done early. A NatHERS assessor can test options while the design is still flexible.
• Build what was modelled. The rating assumes specific products and details. If the windows, insulation or details change on site, the result may change too. Any substitution should be checked against the assessment first.
• Ask about running costs. The Department of Planning states that the new standard cuts thermal energy use by at least 20 per cent. Whether that saving justifies a particular upgrade for your home is worth discussing.

How we approach it

We treat energy and thermal performance as part of the brief, not something to check off at the end. That means raising it during design, confirming that the products specified match the assessment, and checking the installation of insulation and glazing on site before it is covered up.

Requirements differ by project type and location, and they are updated from time to time, so check the current BASIX requirements with your certifier. If you are planning a new home, get in touch and we can talk through your options.

Sources

• Sustainability standards for residential development (BASIX), NSW Department of Planning, Housing and Infrastructure
• BASIX pause to help home buyers and builders, NSW Department of Planning
• Nationwide House Energy Rating Scheme (NatHERS)

This article is general information, not advice for your project. Confirm current requirements with your certifier and the NSW Planning Portal. Full website disclaimer