Sydney’s New Homes Just Got a Lot Harder to Heat and Cool — On Purpose
Australia’s largest city is quietly running one of the country’s biggest experiments in green building, and almost none of it is visible from the street. Since October 2023, every new house approved in New South Wales has had to meet a materially tougher energy standard — a 7-star thermal performance rating, up from the 5.5 to 6 stars that was typical before. The change arrived through the state’s Sustainable Buildings SEPP, which lifted the long-running BASIX scheme to align with the National Construction Code 2022.
It sounds like a bureaucratic footnote. In practice it is one of the most effective decarbonisation levers a city has, because a house built badly in 2026 will still be leaking energy in 2086.
What a star actually measures
The Nationwide House Energy Rating Scheme (NatHERS) scores a dwelling from 0 to 10 based on how much energy it needs to stay comfortable across a full year, adjusted for local climate. A 10-star home needs essentially none. A 0-star home is a tent with a mortgage.
The jump from 6 to 7 stars is worth more than the single-digit increment suggests: in most locations, a 7-star home requires 20 to 25 per cent less energy for heating and cooling than a 6-star equivalent. Given that space conditioning is the single largest slice of household energy use in most Australian homes, that reduction flows straight through to bills and to grid demand at exactly the moments the grid is most stressed — summer afternoons and winter evenings.
NSW paired the thermal uplift with a tighter BASIX energy target, worth roughly a 7 to 11 per cent additional cut in greenhouse emissions depending on the type and size of the development. There are carve-outs — apartment buildings up to five storeys and parts of the North Coast were exempted where the cost-benefit case didn’t hold — but for detached houses across greater Sydney, the new floor is the floor.
The unglamorous engineering behind it
What’s interesting about the 7-star standard is how little of it depends on expensive technology. The cheapest path to compliance is orientation: putting living areas on the northern side of the block and shading them properly from high summer sun. It costs nothing at the design stage and it is nearly impossible to retrofit later.
From there the levers are familiar to anyone who has followed passive house design — ceiling, wall and underfloor insulation matched to the climate zone; high-performance glazing that resists winter heat loss and summer heat gain; careful window sizing on poorly oriented lots; and air sealing to stop conditioned air escaping through gaps. Sydney’s mild winters mean the binding constraint is usually summer overheating rather than heating load, which pushes designs toward eaves, external shading and thermal mass rather than the heavy insulation that dominates colder markets.
Alongside the thermal rating sits a separate “whole-of-home” energy budget covering fixed appliances — hot water, heating and cooling, lighting, pool pumps — with credit for on-site solar. That second test makes all-electric, solar-ready homes the path of least resistance, and is steadily pushing new gas connections out of the Sydney market without anyone having to ban them.
Why the build matters more than the retrofit
Retrofitting an existing house to 7-star equivalence is possible but expensive and disruptive; getting there in a new build costs a fraction as much because the decisions are made on paper. It is the core argument for treating construction standards as climate policy rather than housing policy. Sydney will add tens of thousands of dwellings over the next decade, in greenfield release areas and through knockdown-rebuild in established suburbs. Each one is a fifty-to-eighty-year commitment to a level of energy consumption.
For households, the standard also changes what’s worth asking about. Volume builders now compete partly on how they hit the target — whether through genuine passive design and better glazing, or through the minimum-compliance route of bolting on a bigger air conditioner and more solar panels. The difference doesn’t show up in the star rating, but it shows up in comfort and in running costs. Most establishedhome builders in Sydney now publish how their designs handle BASIX, orientation and sloping sites, and that documentation is worth reading closely before anyone signs a contract.
The wider lesson
Sydney is a reminder that green building progress rarely arrives as a headline technology. It arrives as a revised code, a thicker wall, a window facing the right direction, and a compliance certificate nobody reads. Multiplied across a city of five million, those unremarkable decisions add up to one of the largest emissions reductions available to any metropolis — locked in at construction, and paid back every year the house stands.