Frequently Asked Questions

NatHERS stands for the Nationwide House Energy Rating Scheme. It is Australia''s national system for rating the energy efficiency of residential buildings on a scale of 0 to 10 stars. The rating measures how much energy a home''s building envelope (walls, roof, floor, windows and doors) needs for heating and cooling to maintain comfortable indoor temperatures. A higher star rating means less energy is required, resulting in lower energy bills and greater comfort.

Yes, in most Australian states and territories a NatHERS assessment (or an equivalent compliance pathway) is required for all new residential buildings as part of the building permit process. The National Construction Code references NatHERS as one of the approved methods for demonstrating energy efficiency compliance. Some states, such as New South Wales, have their own systems (BASIX) that may incorporate NatHERS assessments as part of the approval process.

A NatHERS assessment for a standard single-storey home typically costs between $300 and $600. Double-storey homes generally range from $500 to $800, while complex or large custom homes may cost $700 to $1,200 or more. Prices vary depending on the assessor''s location, experience, and the complexity of the design. Most assessors include one to two rounds of design revisions in their quoted fee.

Under the National Construction Code (NCC) 2022, new homes across most of Australia must achieve a minimum NatHERS rating of 7 stars, up from the previous requirement of 6 stars. This increase took effect from 1 October 2023 in most jurisdictions, though some states had transitional arrangements. The NCC 2022 also introduced Whole of Home energy provisions that consider the total energy use of fixed appliances in addition to the building envelope.

There are four NatHERS-accredited software tools: FirstRate5 (widely used in Victoria and other states), AccuRate (developed by CSIRO), BERS Pro (popular in Queensland and northern Australia), and Hero (a newer cloud-based tool). All four use the same underlying Chenath calculation engine developed by CSIRO, so they produce comparable results for the same design. Assessors typically specialise in one or two tools.

A typical NatHERS assessment takes 3 to 7 business days once the assessor receives complete architectural plans and specifications. The actual modelling work usually takes a few hours, but turnaround time depends on the assessor''s workload and the complexity of the design. If design revisions are needed to achieve the target star rating, additional time is required for each iteration. Providing complete and accurate plans upfront is the best way to minimise delays.

Yes, there are many ways to improve the energy performance of an existing home. The most cost-effective upgrades include adding or topping up ceiling insulation, draught sealing around doors and windows, installing ceiling fans, and adding external shading to west-facing windows. More significant improvements include upgrading to double glazing, adding wall insulation, and improving sub-floor insulation. While you are not legally required to meet current NatHERS standards for an existing home, these improvements will reduce energy bills and increase comfort.

A NatHERS assessor evaluates the thermal performance of the building envelope using your architectural plans and specifications. Key factors include building orientation relative to the sun, insulation levels in the ceiling, walls and floor, window sizes and glazing types, shading from eaves and external structures, construction materials and their thermal mass, and airtightness. The assessor models all of these elements in accredited software to calculate the predicted heating and cooling energy loads for your specific climate zone.

NatHERS is a national scheme that rates the thermal performance of the building envelope on a 0 to 10 star scale. BASIX (Building Sustainability Index) is a New South Wales-specific planning tool that sets targets for water, energy, and thermal comfort. BASIX uses NatHERS-accredited software to assess the thermal comfort component, so the two systems are complementary rather than competing. In NSW, you need to meet BASIX requirements to obtain development approval, and the thermal comfort component aligns with NatHERS methodology.

It depends on the scope of the renovation. Generally, a NatHERS assessment is required when you are adding an extension that increases the conditioned floor area, undertaking major renovations that significantly alter the building envelope, or converting an unconditioned space into a habitable room. Minor renovations such as kitchen or bathroom fitouts that do not change the building envelope typically do not require an assessment. Requirements vary between states and councils, so check with your local building surveyor.

NatHERS divides Australia into 69 distinct climate zones, each representing a geographic area with similar weather patterns. Each zone has its own set of hourly climate data that the assessment software uses to calculate star ratings. Climate zones account for differences in temperature, humidity, solar radiation, and wind patterns across Australia. The same house design will receive different star ratings in different climate zones because the heating and cooling demands vary significantly between locations.

You can find your NatHERS climate zone by entering your postcode or suburb into our climate zone lookup tool. Each suburb in Australia is mapped to one of the 69 NatHERS climate zones. You can also check the official NatHERS website at nathers.gov.au, or simply ask your NatHERS assessor — identifying the correct climate zone is one of the first steps they perform when starting an assessment.

Whole of Home (WoH) is a new requirement introduced in the NCC 2022 that goes beyond the traditional NatHERS star rating. While the star rating assesses only the thermal envelope (heating and cooling), the WoH provisions set an overall energy budget for the home that includes fixed appliances such as hot water systems, lighting, HVAC equipment, and pool pumps. Rooftop solar PV can provide a credit against the energy budget. This encourages a holistic approach to home energy efficiency rather than focusing solely on the building shell.

Yes, all NatHERS assessors must hold current accreditation from one of three Accrediting Authority Organisations (AAOs): the Australian Building Sustainability Association (ABSA), Design Matters National (DMN), or the House Energy Rating Association (HERA). Accreditation requires completing approved training, demonstrating competency in NatHERS-accredited software, and maintaining ongoing professional development. Only assessments performed by accredited assessors are accepted by building surveyors and councils for compliance purposes.

Major changes to NatHERS requirements typically occur when the National Construction Code (NCC) is updated, which happens on a roughly three-year cycle. The most recent significant change was the NCC 2022, which raised the minimum star rating from 6 to 7 stars and introduced Whole of Home provisions. Between major NCC updates, the NatHERS scheme may update climate zone data files, software accreditation requirements, or technical protocols. State and territory governments may also adjust their adoption of NCC provisions on their own timelines.

A 7-star home uses approximately 25 to 30 percent less energy for heating and cooling than a 6-star home. In practical terms, achieving 7 stars typically requires better insulation (especially in walls and floors), double glazing in most climate zones, more careful window placement and shading design, and improved airtightness. The additional construction cost is generally estimated at $3,000 to $7,000 for a standard home, which is typically recovered within 5 to 10 years through reduced energy bills.

Yes, NatHERS assessments can be performed on apartments and multi-unit dwellings. Each individual unit within a development is assessed separately, as different units may achieve different star ratings depending on their position in the building, orientation, and exposure to the elements. Corner units and top-floor units, for example, typically have more external wall and ceiling area, which affects their thermal performance. The NatHERS-accredited software tools can model apartments within larger building structures.

If your home design does not achieve the minimum 7-star rating required under NCC 2022, you will not receive a compliance certificate and your building permit may not be approved. However, this is rarely a dead end. Your NatHERS assessor can identify specific design changes to improve the rating, such as upgrading insulation, improving glazing specifications, adjusting window sizes or adding shading. Most designs can be brought up to 7 stars through targeted modifications without major cost increases. Engaging an assessor early in the design process is the best way to avoid this situation.