Table of Contents
What is Passive Design?
Passive design is an architectural approach that leverages a building’s structure and materials to maintain comfortable indoor temperatures with minimal mechanical intervention. Integrating passive design principles into buildings enhances energy efficiency, thermal comfort, and long-term sustainability.
Occupants enjoy reduced reliance on artificial heating and cooling and improved year-round comfort. For builders, incorporating passive design from the outset helps ensure regulatory compliance and smoother project execution.
Passive design aligns with various assessment tools and regulations, including NatHERS (Nationwide House Energy Rating Scheme), BASIX (Building Sustainability Index – NSW), and more.
These tools evaluate a building’s energy efficiency, thermal comfort, and indoor environment quality, all of which are enhanced by passive design strategies.
By incorporating passive design principles, builders can create buildings that are not only energy-efficient but also comfortable, sustainable, and valuable. Thermal modelling complements this approach by providing data-driven insights that optimise design decisions and support regulatory compliance.
Benefits of Passive Design
Passive building design offers benefits that are both substantial and measurable.
According to YourHome.gov.au, good passive design can halve energy use and greenhouse gas emissions, resulting in savings of up to 40% on heating and cooling bills.
This significant reduction in energy consumption not only benefits the environment but also translates to substantial cost savings for building owners. Some of the key benefits of passive design include:
- Lower Energy Bills: Reduced need for heating and cooling means lower energy cost and bill savings.
- Improved Indoor Comfort: Passive design ensures a comfortable indoor temperature across seasons, enhancing occupant well-being and productivity.
- Environmental Benefits: By reducing carbon footprint and promoting sustainable construction, passive design contributes to a more environmentally friendly built environment.
- Increased Resale Value: Buildings designed with passive design principles can command higher resale values and attract buyers who value sustainability and energy efficiency.
- Easier Compliance: Passive design makes it easier to meet energy efficiency reports and sustainability ratings, streamlining the compliance process and reducing administrative burdens.
By incorporating passive design principles, builders can create buildings that are not only energy-efficient but also comfortable, sustainable, and valuable.
In the following sections, we’ll delve deeper into the key principles and strategies for achieving passive design in buildings.
The Role of Energy Efficiency Reports in Passive Design
NatHERS (Nationwide House Energy Rating Scheme)
NatHERS is a national star rating system that assesses a home’s thermal performance. It considers passive design elements such as orientation, solar access, insulation, glazing, ventilation, and thermal mass.
Achieving a high NatHERS rating is beneficial for homeowners and developers, as it indicates a building’s energy efficiency and thermal comfort.
BASIX (Building Sustainability Index – NSW)
BASIX is a mandatory sustainability certification for residential developments in New South Wales. It evaluates water, energy, and thermal comfort.
Passive design elements such as window-to-wall ratios, insulation levels, solar orientation, natural ventilation, and shading are crucial in meeting or exceeding BASIX compliance.
Other Relevant Tools
Green Star (Green Building Council of Australia)
A voluntary sustainability rating that includes credits for energy efficiency, thermal comfort, and indoor environment quality. Green Star ratings are based on a building’s design and performance, and passive design strategies can contribute to achieving higher ratings.
National Construction Code (NCC - Section J)
Sets minimum energy efficiency standards, which passive design helps buildings meet or exceed. By incorporating passive design principles, builders can ensure their buildings comply with NCC Section J requirements.
Passive House (Passivhaus) Certification
A globally recognised performance standard focusing on airtightness, high insulation, and minimal thermal bridging. Passive House certification requires buildings to meet strict energy efficiency standards, and passive design is a key component of achieving this certification. Visit the Australian Passivhaus Association website for more information.
Key Passive Design Principles
Climate-Responsive Design
Climate-responsive design is a cornerstone of passive design, focusing on tailoring building features to the specific climate in which the structure is located. Australia has eight distinct climate zones, ranging from tropical to cool temperate, each with its own challenges and opportunities for passive design strategies.
By analysing local factors such as temperature variations, humidity, wind patterns, and solar exposure, building designers can integrate strategies that naturally moderate indoor temperatures, reducing reliance on artificial heating and cooling.
Practical measures include adjusting building orientation, selecting appropriate insulation, optimising glazing, and implementing shading solutions that match the local climate zone.
For example, in hot climates, deep eaves or pergolas can block summer sun, while in cooler regions, north-facing windows can maximise winter solar gain.
This approach not only enhances occupant comfort but also aligns with NatHERS assessments of thermal performance and supports BASIX compliance by ensuring that building design is both climate-appropriate and energy-efficient.
To learn more about Australia’s eight climate zones and how to design effectively for each, visit YourHome.gov.au.
Passive Heating
Passive heating involves capturing sunlight to naturally warm indoor spaces, reducing the need for artificial heating systems.
By incorporating design features like north-facing windows, thermal mass materials, and effective insulation, buildings can harness and retain solar heat, enhancing year-round comfort.
In the NatHERS assessment, passive heating contributes to higher star ratings by improving solar heat gain and efficient heat retention, while BASIX requires that heating solutions do not rely excessively on mechanical systems.
For example, large north-facing windows can be paired with thermal mass elements like concrete or brick to absorb heat during the day and release it at night, supporting both occupant comfort and compliance with energy efficiency standards.
Passive Cooling
Passive cooling leverages natural ventilation and shading to maintain comfortable indoor temperatures, reducing dependence on artificial cooling systems.
Key strategies in passive cooling include:
- Facilitating cross-ventilation and stack ventilation
- Using shading devices to block direct sunlight
- Incorporating reflective materials to deflect heat
In warm and temperate climates, designing openings on opposite sides of a building encourages air movement, while adjustable shading helps manage seasonal changes in solar exposure.
In the NatHERS framework, passive cooling is assessed based on its effectiveness in managing ventilation and reducing overheating risks. For BASIX compliance, well-designed passive cooling helps manage cooling loads, contributing to a building’s overall energy efficiency and occupant comfort.
Building Orientation
Building orientation is a fundamental aspect of passive design, determining how a structure interacts with the sun’s path and prevailing winds.
By thoughtfully positioning the building – ideally with living areas facing north in the Southern Hemisphere – designers can maximise winter solar gain and harness natural ventilation. In addition, strategic placement of windows and shading devices can mitigate summer heat while maintaining daylight access.
Within NatHERS assessments, orientation directly influences a home’s star rating by affecting heating and cooling loads, while BASIX evaluates orientation as part of its solar access and energy efficiency requirements.
Incorporating optimal orientation strategies from the outset enhances occupant comfort and simplifies compliance with key energy performance standards.
Thermal Mass
Thermal mass refers to the capacity of building materials to absorb, store, and slowly release heat, moderating indoor temperatures throughout the day and night.
Materials like concrete, brick, and stone, when integrated into floors or walls, can absorb heat during the day and release it when temperatures drop, reducing the need for artificial heating and cooling.
In NatHERS assessments, the effectiveness of thermal mass is evaluated based on its placement and interaction with other design elements, while BASIX encourages using thermal mass to support stable indoor temperatures.
Thoughtful integration of thermal mass enhances occupant comfort, reduces peak heating and cooling demands, and contributes to long-term energy efficiency.
Insulation
Insulation plays a vital role in passive design by limiting heat transfer between the interior and exterior of a building, maintaining comfortable temperatures year-round.
Effective insulation reduces the demand for artificial heating and cooling systems, contributing to lower energy bills and improved thermal comfort. Common insulation types, such as bulk insulation, reflective foils, and rigid boards, can be used in walls, ceilings, and floors to create a continuous thermal barrier.
NatHERS assessments consider the R-values of insulation to evaluate its contribution to a building’s star rating, while BASIX sets minimum standards for insulation thickness and performance based on climate zone.
Careful specification and installation of insulation are key to achieving energy-efficient design outcomes.
Glazing
Glazing encompasses windows and other transparent elements that influence daylight, heat gain, and thermal comfort within a building.
Energy-efficient glazing strategies, such as double glazing, low-emissivity (Low-E) coatings, and optimised window placement, can significantly reduce unwanted heat transfer and improve the balance between natural light and energy performance.
Within the NatHERS framework, window size, orientation, and performance metrics like solar heat gain coefficient (SHGC) are critical factors in determining star ratings. BASIX guidelines require careful management of glazing ratios to optimise energy efficiency and thermal comfort.
By selecting appropriate glazing solutions and integrating shading, designers can enhance both occupant wellbeing and compliance outcomes.
Shading
Shading strategies are essential for managing solar heat gain and controlling indoor temperatures, particularly during the warmer months.
External shading devices such as eaves, pergolas, and adjustable louvres can block high-angle summer sun while allowing beneficial winter sunlight to penetrate and warm interior spaces.
Effective shading design reduces the need for artificial cooling, enhancing occupant comfort and energy efficiency.
NatHERS assessments model shading effectiveness in influencing cooling loads and overall performance, while BASIX provides guidance on shading design tailored to different climate zones.
By integrating responsive shading solutions, designers can strike the right balance between comfort, energy use, and regulatory compliance.
Ventilation and Airtightness
Ventilation and airtightness are interrelated aspects of passive design that together enhance thermal comfort, energy efficiency, and indoor air quality.
Effective natural ventilation strategies, such as cross-ventilation, stack effect, and operable windows, allow fresh air to enter and stale air to exit, reducing reliance on artificial systems and improving occupant wellbeing.
Meanwhile, airtight construction prevents uncontrolled air leaks that can undermine insulation and heating or cooling performance, ensuring that the building envelope performs as intended.
NatHERS evaluates ventilation and airtightness to balance fresh air needs with energy efficiency, while BASIX outlines measures to maintain appropriate indoor air quality without compromising the building’s thermal envelope.
A well-designed balance of controlled ventilation and airtightness helps buildings achieve optimal energy performance and comfortable indoor conditions.
Condensation Management
Condensation management is critical in passive design to maintain healthy indoor environments and preserve building integrity. It involves strategies that prevent moisture accumulation on interior surfaces, which can lead to mould growth, material degradation, and poor air quality.
Techniques that can effectively reduce condensation risks include:
- Ensuring continuous insulation,
- Managing indoor humidity levels, and
- Integrating controlled ventilation systems
While not a direct component of NatHERS assessments, condensation management supports BASIX compliance by addressing moisture control requirements to protect occupant health and building durability.
By proactively managing condensation, designers and builders can ensure passive buildings remain comfortable, safe, and energy-efficient throughout their lifespan.
Passive House Standard
The Passive House standard is an internationally recognised benchmark for energy-efficient building performance, focusing on creating highly insulated, airtight, and thermally bridge-free envelopes that minimise the need for active heating and cooling.
Adopting Passive House principles, such as advanced insulation systems, meticulous airtight construction, and optimised window and shading design, results in buildings that maintain comfortable temperatures with very low energy use.
While separate from Australia’s NatHERS system, Passive House designs often exceed NatHERS star ratings and align with, or surpass, BASIX requirements for thermal comfort and energy efficiency.
By pursuing Passive House certification, designers and builders can demonstrate a commitment to exceptional building performance, occupant comfort, and sustainability.
Thermal Modelling
The Passive House standard is an internationally recognised benchmark for energy-efficient building performance, focusing on creating highly insulated, airtight, and thermally bridge-free envelopes that minimise the need for active heating and cooling.
Adopting Passive House principles, such as advanced insulation systems, meticulous airtight construction, and optimised window and shading design, results in buildings that maintain comfortable temperatures with very low energy use.
While separate from Australia’s NatHERS system, Passive House designs often exceed NatHERS star ratings and align with, or surpass, BASIX requirements for thermal comfort and energy efficiency.
By pursuing Passive House certification, designers and builders can demonstrate a commitment to exceptional building performance, occupant comfort, and sustainability.
Putting Passive Design into Practice
Passive design is a cornerstone of energy-efficient and sustainable building practices. By incorporating passive strategies, such as climate-responsive design, effective orientation, and thermal mass, builders can significantly reduce energy consumption, enhance occupant comfort, and meet regulatory standards like NatHERS and BASIX.
Green Choice Consulting offers expert guidance in NatHERS energy assessments and BASIX certification, ensuring your project aligns with both performance and compliance requirements.
Engaging our expertise early in the design phase helps architects and builders create buildings that are not only environmentally responsible but also cost-effective and comfortable.
Contact Green Choice Consulting today to discuss your project’s energy efficiency and explore how passive design can transform your building’s performance.
Albert Burton is the founder of Green Choice Consulting, leading a national team that delivers fast, accurate ESD reports for residential and commercial projects. With expertise in sustainability and business, he leverages advanced technology to streamline compliance and reduce costs for clients.
