A simple guide to energy ratings, comfort and everyday living in Australian homes
When planning a new home, terms like Passive Solar Design, NatHERS and Passivhaus often come up early in the process. They can sound similar, but they describe different approaches to comfort, energy use and how homes are designed and built.
This guide explains what each term means, how they differ, and what they can mean for the comfort and energy efficiency of your home.
What is Passive Solar Design?
Passive Solar Design is an approach that works with the local climate to help maintain comfortable indoor temperatures, reducing the need for additional heating and cooling. It often relies on occupants interacting with the home, such as opening and closing windows, blinds or doors, to work effectively.
Passive Solar Design typically considers:
- building orientation
- natural ventilation
- passive solar heating
- passive cooling strategies
- thermal mass
- glazing selection
- shading
- insulation
Used well, these strategies can significantly improve comfort and reduce energy use, particularly when matched carefully to climate and lifestyle.
What is NatHERS?
NatHERS (Nationwide House Energy Rating Scheme) is Australia’s national home energy rating system. It gives homes a star rating out of 10 based on predicted heating and cooling demand.
NatHERS is the most common way new homes, townhouses and apartments meet minimum energy efficiency requirements under the National Construction Code (NCC) and has played an important role in improving the baseline quality of Australian housing.
NatHERS is particularly useful when:
- responding to Australian climate conditions
- supporting passive solar design strategies
- understanding comfort room by room
- meeting regulatory requirements
NatHERS does, however, rely on assumptions about how people live in their homes, such as when rooms are heated or cooled and how often windows are opened. In practice, homes are often used quite differently.
What is Passivhaus?
Passivhaus (Passive House) is a voluntary international building standard focused on delivering steady indoor comfort with very low energy use. It is based on clearly defined and measurable performance requirements rather than assumptions about how a home might be used.
Passivhaus focuses on:
- airtight construction
- a well insulated building envelope
- reduced thermal bridging
- high quality window glazing
- fresh air supplied through a heat recovery ventilation system
A key distinction is that Passivhaus homes are checked during construction, including post construction airtightness testing, helping ensure the home performs as designed, not just as modelled.
Key differences between NatHERS and Passivhaus
At a high level, the differences come down to how comfort, air quality and certainty are approached.
Airtightness
- Passivhaus requires the building envelope to be tightly sealed and verified on site.
- NatHERS assumes air leakage based on construction type and does not require testing.
Ventilation
- Passivhaus relies on a dedicated ventilation system that supplies fresh, filtered air while removing stale air. Windows can still be opened, but fresh air does not depend on them.
- NatHERS generally assumes fresh air is provided through opening windows.
Thermal bridging
- Passivhaus looks closely at all the places where heat can escape through the building, such as corners, junctions and structural elements, and requires these weak points to be carefully designed to reduce heat loss.
- The NCC sets minimum requirements to manage common problem areas, like metal wall framing, but does not assess every junction in detail.
Comfort
- Passivhaus aims for stable indoor temperatures throughout the home.
- NatHERS allows wider temperature variation depending on climate, room type and time of day.
Indoor air quality
- Passivhaus actively considers fresh air, humidity and moisture management.
- NatHERS focuses primarily on heating and cooling demand.
Thermal mass and passive design
- Passivhaus uses a fabric first approach, with insulation and airtightness prioritised over thermal mass.
- NatHERS places greater emphasis on thermal mass as part of its assessment process.
Certainty once built
- Passivhaus includes independent verification during construction.
- NatHERS is typically assessed at design stage, with limited verification after construction.
A note on cost
Homes designed to meet Passivhaus standards can involve a higher upfront investment in Australia, particularly where formal certification is pursued. The extent of this varies by project and is influenced by design decisions, detailing and construction experience.
For many clients, this is weighed alongside benefits such as comfort, indoor air quality, acoustic performance and confidence that the home will perform as intended once built.
Why this conversation matters
At the end of the day, NatHERS and the Passivhaus Standard are tools. What truly matters is how a home feels to live in.
A well designed home should be comfortable in all seasons, filled with fresh air, and supportive of health and wellbeing without relying on constant heating or cooling. It should use less energy, last longer and tread more lightly on the planet.
At Fluit Studio, Passive Solar Design sits at the foundation of our work. Whether a project is pursuing a NatHERS rating or aiming for certified Passivhaus, we use climate responsive design strategies to shape homes that are comfortable, efficient and suited to the way people actually live.
Both pathways are working toward the same outcome, sustainable, comfortable homes. They simply place emphasis on different aspects of how that comfort is achieved and verified. Our role is to help clients understand those differences and make informed choices that align with their goals, site and budget.
When comfort, health and efficiency are considered from the outset, homes become calmer and more resilient places to live, supporting everyday life now and into the future.
We use energy modelling to inform better decisions, but our focus is always on people first, creating homes that are comfortable, healthy and considered in their impact on the environment.
