Why Your New WA Home Needs a 7-Star Energy Rating (And What That Means for Your Design)

A single design decision made at concept stage can add/cost $20,000 to your build. Nowhere is that more true than in energy performance, where getting the fundamentals right from the start costs nothing, and fixing them later costs a great deal.

All new homes in WA are now required to achieve a minimum 7-star energy rating under the Nationwide House Energy Rating Scheme (NatHERS). This is a significant step up from previous standards, and it affects far more than just your insulation choice.

A 7-star rating assesses the entire thermal performance of your home — how it heats up, how it cools down, and how much energy you need to keep it comfortable year-round. Design decisions you might consider cosmetic or minor can have a major impact on your score.

What the 7-star requirement affects

•      Insulation - ceiling and wall insulation R-values must meet higher standards. The specification matters more than ever.

•      Window placement and size - north-facing glazing captures winter sun; east and west-facing windows create heat load in summer. Your window layout must be deliberate.

•      Shading - eaves, pergolas, and window hoods are now functional design tools, not just aesthetics. They manage solar gain and reduce cooling burden.

•      Materials - thermal mass (brick, concrete) regulates internal temperatures naturally, reducing reliance on mechanical systems.

A real example of the difference good design makes

A recent four-bedroom home in Busselton initially modelled at 6.4 stars. By adjusting glazing ratios — reducing west-facing glass by 30% and increasing north-facing glazing — and extending eave depth to 600mm on the north elevation, the same floor plan achieved 7.2 stars. No change to insulation specification. No change to construction cost. Just better design decisions.

This is why we consider NatHERS compliance a design exercise, not a compliance checkbox at the end.

The cost of getting it wrong

Retrofitting a home to improve its energy rating after construction is significantly more expensive than building it correctly the first time. Replacing windows, adding external shading, or upgrading insulation post-build costs multiples of what those decisions would have added at the design stage.

Whether you're building in Bunbury, Margaret River, or anywhere in the South West, the climate zone considerations are similar, hot dry summers, mild winters, and the need to manage both solar gain and overnight cooling.

Frequently Asked Questions

What is a NatHERS energy rating?

NatHERS (Nationwide House Energy Rating Scheme) uses thermal modelling software to predict how much energy a home will need for heating and cooling. It rates homes on a scale of 0–10 stars, with 10 being passive, needing no mechanical heating or cooling at all. WA now requires a minimum of 7 stars for all new homes.

Does the 7-star requirement apply to renovations?

The 7-star NatHERS requirement applies to new homes. Additions and alterations are subject to different NCC provisions, but significant extensions may trigger energy compliance obligations. Always check with your building designer before starting.

How much does improving from 6 to 7 stars typically cost?

In most cases, very little, if the design is approached correctly from the start. Orientation, eave depth, and window placement cost nothing to get right. Where additional insulation or glazing upgrades are required, the cost is typically $2,000–$8,000, which is generally recovered in reduced energy bills within a few years.

Want to design a home that meets 7 stars and actually saves you money on bills? Send us your Block details and we'll talk through what's possible, fastlane.drafting@gmail.com