Decoding Sustainable Homes: BASIX, NatHERS, Passive House and Passivhaus Explained
The terminology around sustainable homes can feel complex. Terms like BASIX, NatHERS, and Passive House, often confused with Passivhaus, the European standard, often come up when people start exploring sustainability standards and guidelines. While they’re not interchangeable, the overlap in their use can cause confusion, what does each one mean, and which should you follow? Understanding the distinctions is key to making informed choices about comfort, energy efficiency, and long-term performance in your home.
BASIX: New South Wales’ Compliance Gateway
BASIX (Building Sustainability Index) is a mandatory framework for all new residential developments and many renovations in New South Wales. Its focus is compliance with minimum sustainability targets in three areas: water use, energy consumption, and thermal comfort.
It works as a pass/fail system. You enter the details of a proposed design, and BASIX confirms whether it meets the legislative requirements. While straightforward, it’s also limited in flexibility.
One notable aspect is that BASIX can draw on other systems, such as NatHERS or Passive House, for its thermal comfort calculations. In fact, its thermal comfort assessment draws on the NatHers rating system to mark compliance.
NatHERS: Australia’s Star Rating System
NatHERS (Nationwide House Energy Rating Scheme) is a national framework that evaluates the thermal performance of homes, expressed through a star rating from 0 to 10. The higher the rating, the better the home design performs in maintaining comfortable indoor temperatures with minimal energy use.
It estimates the amount of energy needed for heating and cooling considering the home’s design features such as orientation, window glazing and insulation.
In New South Wales, a 7-star NatHERS rating is needed to satisfy the thermal comfort component within BASIX. Where BASIX is rigid, NatHERS provides greater flexibility and insight. Designers can model and compare multiple design options, providing a more detailed picture of how a home will behave thermally.
Passive House vs Passivhaus
In Australia “Passive houses” are commonly referred to as houses that employ passive environmental heating and cooling design principles and a design approach that aims for high energy efficiency and comfort by using passive solar heating, thermal mass, insulation, orientation and ventilation
It can also be used loosely — for example, people might describe a well-insulated, low-energy home as a “passive house” even if it hasn’t been formally tested or certified.
Passivhaus which of course is German for “Passive House”, refers specifically to buildings that meet the official Passivhaus Institute (PHI) standard, developed in Germany in the 1990s.
This is a rigorous, measurable certification system with strict criteria for:
Heating and cooling demand (≤15 kWh/m² per year each)
Primary energy demand
Airtightness (tested with a blower door test, max 0.6 air changes per hour)
Thermal comfort requirements
Certification is audited by accredited Passivhaus designers/consultants and ensures the building meets a globally consistent benchmark. Although not a common standard in Australia it does have a dedicated user group.
Passivhaus: A Global Benchmark
Passivhaus is a voluntary, international building standard recognised for its uncompromising focus on comfort, health, and performance. Unlike NatHERS, which primarily measures energy efficiency, Passivhaus encompasses a wider set of principles designed to create highly controlled, predictable, and healthy indoor environments.
Key aspects of Passive House include:
Precision and Accuracy. Performance modelling is highly detailed, delivering predictions that closely match real-world results, provided construction follows the standard.
Air Tightness Testing. Every certified Passivhaus must undergo a blower door test to measure how much air leaks in and out, a critical factor for energy efficiency and comfort.
Healthy Indoor Air. Homes use heat recovery ventilation systems (HRV) to continually deliver filtered, fresh air while maintaining indoor temperatures and removing pollutants, allergens, and even bushfire smoke.
Climate Adaptability. The principles of air tightness, insulation, and controlled ventilation work in all climates, with specific details tailored to local conditions.
Cost and Design Considerations. Building to Passivhaus standards is always going to cost significantly more than a project home, but it can be comparable to a custom architectural build. Compact, efficient forms work best, though larger homes with expansive glazing are possible with higher investment in specialised systems. Importantly, Passivhaus requires collaboration from the earliest design stages between architects, energy assessors, and builders.
How They Relate: Compliance vs. Performance
BASIX – The compliance requirement in New South Wales, focused on minimum standards.
NatHERS – A national star rating system that offers flexibility and a deeper look at thermal performance.
Passive House – A term commonly attributed to a house that uses passive heating, thermal mass and natural ventilation for a more comfortable home but not a standard as such
Passivhaus - A gold standard for health, comfort, and predictability, which exceeds compliance requirements.
Together, they form a spectrum: BASIX ensures legal compliance, NatHERS provides detailed thermal insights, and Passivhaus Accreditation delivers a holistic, performance-driven outcome and a high-performance product.
For homeowners, the choice depends on priorities and what they can and want to invest. It may simply come down to meeting regulations or there might be a desire to achieve higher efficiency and comfort for environmental and health concerns.
Ready to explore the right pathway for your project? Get in touch with us today to discuss how we can help shape your sustainable home.
Want to understand how upcoming regulations will impact property owners and investors? Check out our blog: Energy Efficiency Rules for Rental Properties are Changing, here’s what you need to know.
