Design Considerations / Comfort & Energy / Approvals & ratings
NSW BASIX explained
In NSW, every new home and most significant renovations need a BASIX certificate before they can be approved. BASIX sets targets for water, energy and thermal comfort, and records the materials used. The commitments on the certificate then become part of the approval, and they're checked before you can move in.
Design ConsiderationsComfort & EnergyAt a glance
BASIX is NSW's sustainability requirement for homes. A certificate sets targets for water, energy and thermal comfort, and records the embodied emissions of the materials. Its commitments must be shown on the plans, built as listed, and confirmed before you can move in.
- You need one for every new home, alterations of $50,000 or more, and pools of 40,000 litres or more.
- Thermal: seven NatHERS stars for most new homes since October 2023, plus heating and cooling caps.
- Energy and water targets are percentage cuts from a benchmark home, and they vary by location.
- The Materials Index reports embodied emissions, with no target yet.
- Thermal compliance can be shown three ways: DIY for simple houses, a NatHERS simulation, or Passive House certification.
- Any design change needs a revised certificate, which is free if the original is lodged or still valid.
- The certifier confirms the house matches the certificate before the occupation certificate is issued. Late substitutions are the usual problem.
The basicsWhat BASIX is and when you need it
BASIX, the Building Sustainability Index, is NSW's own system for making homes use less energy and water. It has applied since 2004, and in NSW it takes the place of the National Construction Code's energy rules for homes.
You need a BASIX certificate for:
- every new home, including houses, dual occupancies, townhouses and apartments
- alterations and additions costing $50,000 or more
- swimming pools of 40,000 litres or more
Since it began, more than 500,000 BASIX homes have saved an estimated 12.3 million tonnes of greenhouse emissions and 340 billion litres of drinking water.
The partsWhat BASIX measures
| Section | What it measures | Target |
|---|---|---|
| Thermal performance | How much heating and cooling the building shell will need | Seven NatHERS stars for most new homes since 1 October 2023, plus separate heating and cooling caps for the climate zone |
| Energy | Greenhouse emissions from hot water, heating, cooling, lighting, cooking and pool pumps, less on-site solar | A percentage cut from a benchmark of 3,292 kg of CO2 per person per year, set by location and building type |
| Water | Drinking water used for showers, toilets, washing and gardens | A cut of 0% to 40% from a benchmark of 247.5 litres per person per day, depending on climate zone |
| Materials Index | Embodied emissions in the floors, walls, roof and glazing | Reported only, with no target yet |
The energy and water targets vary by location because climates, rainfall and grid supply differ across the state. The calculator on the NSW Planning Portal shows the exact targets for any site.
ThermalThree ways to comply
- The DIY method is built into the BASIX tool. You enter the construction, insulation, window sizes, glass and shading, and BASIX checks them against fixed rules. It suits simple single houses only, and is limited to 40 windows.
- The simulation method uses a NatHERS assessment by an accredited assessor. The house must reach the seven-star standard and stay under the heating and cooling caps for its climate zone. It works for any design, and gives far more freedom than DIY.
- The Passive House method uses certification under the international Passive House standard, with a certified designer and a blower door test after construction. It's available in some locations.
For anything other than a simple house, the simulation method is usually the better choice. It credits good orientation and design rather than prescribing a fixed specification.
Energy and waterWhat usually gets committed
To meet the energy target, a BASIX house typically commits to some combination of:
- an efficient hot water system, such as a heat pump or solar
- efficient heating and cooling, such as reverse-cycle air conditioning, with ceiling fans
- efficient lighting
- rooftop solar panels, which offset energy use
- an efficient pool pump, if there's a pool
The October 2023 update recalculated energy using a grid emissions factor 37% lower than before, reflecting cleaner electricity. That makes all-electric homes with solar easier to get through.
To meet the water target, common commitments are water-efficient taps, showers and toilets, a rainwater tank connected to toilets, the laundry or the garden, and low-water landscaping. The size of the tank and what it connects to are written onto the certificate.
Every one of these is a commitment. If it's on the certificate, it must be installed.
The same house either side of the border
| ACT | NSW | |
|---|---|---|
| Thermal standard | Seven stars under the NCC, with NCC heating and cooling limits | Seven stars under BASIX, with BASIX heating and cooling caps |
| Energy | NCC Whole of Home score of at least 60 | BASIX energy target, a percentage cut in emissions |
| Water | No equivalent target | BASIX water target of up to 40% less |
| Embodied emissions | Not measured | Materials Index, reported only |
| Ways to comply | NatHERS rating, deemed-to-satisfy, or a performance solution | DIY, NatHERS simulation, or Passive House |
| When it's checked | Building approval and final certification | Development consent or complying development, construction certificate, and a completion receipt before occupation |
The design response is the same either side of the border. The paperwork is not.
The processFrom design to occupation
- Assess and generate the certificate once the design meets every target. It's valid for three months before it's lodged.
- Lodge it with the development application or complying development certificate. Once lodged, it lasts for the life of the application.
- Show the commitments on the plans. The construction certificate drawings must show every BASIX commitment.
- Revise it if the design changes. Any change to the design, such as a bigger window, a different hot water system or a smaller tank, needs a revised certificate. Revising a lodged or still-valid certificate for the same project costs nothing extra.
- Build to it. The certifying authority inspects during construction.
- Get the completion receipt. Before the occupation certificate is issued, the certifier confirms that what was built matches the certificate.
The common failure is a late substitution: a cheaper window, a different water heater or a smaller tank that no one checked against the certificate. It's found at final inspection, when it's expensive to fix.
RenovationsAlterations and additions
Alterations and additions costing $50,000 or more need a BASIX certificate too, usually covering the new work rather than the whole existing house. That typically means commitments for new windows, insulation in new walls and ceilings, and any new fittings or hot water system.
A renovation is also a chance to fix the existing house. Ceiling insulation, sealing and new windows in the old part aren't always required, but they're cheapest to do while the builders are already on site.