Passive design uses the building’s orientation, form, windows, shading, insulation, ventilation and construction to respond to the local climate before mechanical heating and cooling systems are considered.
Within BASIX and NatHERS, these decisions influence the modelled heating and cooling demand of a residential design. A well-coordinated passive response can improve thermal performance, reduce pressure on later specifications and make the final commitments easier to deliver.
Passive design is not a checklist of universally beneficial features. Each measure affects the others, and the appropriate balance depends on the climate, site, dwelling form and way the home is expected to operate.
In Brief
Passive design is a climate-responsive approach that uses the building itself to manage heat, sunlight and air movement. Orientation, glazing, shading, insulation, thermal mass, ventilation and building form are coordinated so the dwelling requires less artificial heating and cooling. Within BASIX and NatHERS, these principles influence the modelled thermal loads, but no single feature guarantees a passing result. The complete design must be assessed for its location and dwelling type.
Knowledge Navigation
Assessment
How early design decisions influence heating and cooling results.
Design System
Orientation, windows, shading, fabric, air movement and thermal mass.
Performance Balance
Why an improvement to one seasonal result can affect the other.
Project Workflow
How passive decisions can be tested before the design is locked.
Mechanical systems respond to the heating and cooling demand created by a home. Passive design seeks to reduce or moderate that demand through the design of the building itself.
The approach considers how sunlight enters the home, where heat is gained or lost, how air can move through the rooms and how construction materials respond to changing temperatures.
A passive response may include useful winter solar access, controlled summer shading, well-positioned operable windows, continuous insulation and an appropriate balance between lightweight and thermally massive materials.
These features are most effective when they are considered together. Adding one nominally efficient product to a poorly coordinated design does not create a complete passive-design strategy.
Thermal Performance
Passive-design decisions primarily influence the thermal-performance section of BASIX. That section assesses the heating and cooling demand associated with the proposed dwelling.
The dwelling must remain within the applicable heating and cooling limits using the selected BASIX thermal-performance method. Depending on the project, this may be the BASIX DIY Method, NatHERS Simulation Method or Passive House Standard method.
Passive design can also influence the wider BASIX Energy result. Lower heating and cooling demand generally reduces the operational energy associated with maintaining indoor conditions. The equipment type and efficiency are assessed separately within the Energy section.
A strong passive response does not replace the BASIX assessment. It creates a better starting point for the project to be modelled, tested and documented.
Understand BASIX thermal performance and heating and cooling loads →
NatHERS software models the proposed dwelling across a standardised year using the project climate, geometry, construction, glazing, shading and other thermal characteristics.
The model calculates the heating and cooling demand of the assessed spaces. Those loads contribute to the overall thermal star rating and, for BASIX Simulation projects, are also compared with the applicable BASIX limits.
NatHERS therefore provides a way to test the combined effect of passive-design decisions. It can show that two visually similar homes perform differently because of orientation, exposure, glazing distribution or shading.
The assessment should be used as design feedback rather than treated only as a final compliance calculation. Testing the model while changes remain possible gives the team more opportunity to resolve the building form before relying on expensive specification upgrades.
Read how NatHERS and BASIX work together →
The principles below work as an interconnected system. Each has its own specialist considerations, but the project result depends on how they are combined.
Principle 01
The dwelling and its rooms are positioned in response to seasonal sun, prevailing weather, views and site constraints.
Principle 02
Window area, placement, operability, frame and glass performance balance heat transfer, solar gain, daylight, ventilation and views.
Principle 03
External shading controls unwanted summer heat while preserving useful light and, where appropriate, winter solar access.
Principle 04
The floors, walls, ceilings, roofs and insulation reduce uncontrolled heat flow between conditioned spaces and external or unconditioned areas.
Principle 05
Operable openings and internal airflow paths support natural cooling, while effective seals reduce unwanted air leakage when openings are closed.
Principle 06
Materials with heat-storage capacity can moderate internal temperature changes when they are exposed to useful solar gain and supported by appropriate ventilation and shading.
Principle 07
Insulation layers, framing and junctions should be resolved so heat does not bypass the intended thermal barrier through avoidable thermal bridges.
Principle 08
Roof colour, solar absorptance, roof-space conditions and external finishes can influence the amount of heat absorbed or transferred into the dwelling.
Climate Response
New South Wales contains a wide range of thermal conditions. A strategy suited to a warm coastal location may not be appropriate for an inland, elevated or cold-climate site.
| Climate Pressure | Design Priority | Typical Coordination Question |
|---|---|---|
| Heating-dominated | Retain heat, control heat loss and capture useful winter solar gain. | Can glazing, insulation and orientation reduce winter heating demand without creating summer overheating? |
| Cooling-dominated | Limit unwanted solar gain and support controlled air movement. | Can shading, window placement, roof response and ventilation reduce summer heat accumulation? |
| Mixed or temperate | Balance useful winter gain with protection from summer and shoulder-season heat. | Which elements should be fixed, adjustable or seasonally operable so both heating and cooling loads remain controlled? |
The correct NatHERS climate file and project address are therefore fundamental to the assessment. A specification that performs well for one site should not be transferred to another project without testing.
Passive design should also respond to site-specific conditions such as neighbouring buildings, vegetation, topography, prevailing winds, noise, bushfire requirements and available solar access.
Many passive-design decisions improve one seasonal result while potentially placing pressure on another. The assessment must therefore test both heating and cooling demand.
Larger or higher-SHGC windows can admit useful winter heat, but poorly controlled solar access can increase summer cooling demand.
Deep fixed overhangs can protect glazing in warm conditions but may also block useful winter sunlight where the geometry is not seasonally responsive.
Thermal mass can moderate temperature changes, but it may retain unwanted heat where it is exposed to excessive summer sun or cannot release stored heat overnight.
Openable windows can support deliberate cooling, while unintended gaps and poorly sealed elements can increase heat loss or heat gain when the building is intended to be closed.
BASIX can apply separate heating and cooling limits. A favourable combined NatHERS result does not necessarily mean that each seasonal outcome is satisfactory.
Integrated Design
Orientation determines when and how sunlight reaches each façade. Window design determines how much of that light and heat can enter or leave the home. Shading determines when direct solar exposure is controlled.
These elements should not be resolved in isolation. A window specification cannot fully correct inappropriate glazing area, and a large fixed overhang may not provide the same seasonal response as well-positioned or adjustable shading.
The project should consider:
Understand SHGC and U-values in BASIX assessments →
Insulation reduces conductive heat transfer through the building fabric. Airtightness reduces uncontrolled air leakage through gaps and junctions. Ventilation deliberately replaces indoor air through openings or mechanical systems.
| Element | Primary Function | Design Question |
|---|---|---|
| Insulation | Slows heat flow through floors, walls, ceilings and roofs. | Is the insulation level and installation continuous and suitable for the construction system? |
| Airtightness | Limits unintended air movement through the closed building envelope. | Are doors, windows, penetrations and junctions capable of being sealed when required? |
| Ventilation | Provides controlled fresh air and can support cooling and moisture management. | Can occupants introduce or remove air intentionally without relying on uncontrolled gaps? |
A tightly sealed dwelling still requires a ventilation strategy. Likewise, operable windows do not remove the need for the closed building envelope to be reasonably sealed.
Understand how airtightness relates to BASIX →
Heat Storage
Thermal mass describes the capacity of materials to absorb, store and later release heat. Concrete, masonry, stone and some floor systems can provide useful thermal mass when they are positioned and exposed appropriately.
In a climate with useful winter sun and cooler nights, mass can absorb daytime heat and release it as temperatures fall. During warm periods, it may help stabilise internal conditions where the stored heat can be removed through night cooling or ventilation.
Thermal mass can be less beneficial where it is permanently shaded in winter, exposed to excessive summer solar gain or prevented from releasing accumulated heat. Floor coverings and internal linings can also change how effectively the mass interacts with the room.
The value of thermal mass should therefore be assessed as part of the complete climate, solar-access, shading and ventilation strategy rather than inferred from the material alone.
An efficient residential design must manage both cold and warm conditions. Increasing insulation or solar access without reviewing summer performance can create high internal temperatures or excessive cooling demand.
Overheating pressure can be increased by:
Passing the BASIX cooling requirement is an important compliance outcome, but it should not be interpreted as a guarantee that the completed home can never overheat under unusual weather, operational or urban conditions.
Explore overheating risk in NSW homes →
Design Workflow
Confirm the project climate, true north, topography, neighbouring development, available solar access and relevant breeze or exposure conditions.
Position living areas, bedrooms, circulation and service spaces in response to solar access, views, privacy and daily patterns of occupation.
Review window area, orientation, performance and operability together with the proposed external shading geometry.
Select construction, insulation, thermal breaks, roof response and sealing provisions that suit the dwelling form and climate.
Provide appropriate operable openings, internal flow paths, ceiling fans or other strategies while maintaining control when the building is closed.
Use the relevant BASIX or NatHERS pathway to identify heating, cooling and dwelling-specific performance outcomes.
Determine whether the project is constrained by heating, cooling or both before selecting a design or specification response.
Coordinate the assessed windows, insulation, construction, shading and ventilation assumptions with the approval and construction information.
Passive-design decisions are usually easier to adjust while the building form, room layout and openings remain under development.
Early assessment can help the project team identify:
This allows the project to resolve fundamental design issues before relying on higher-performing glazing, additional insulation or other late specification changes.
Can a BASIX assessment begin before the plans are finalised? →
A glazing, shading or insulation strategy transferred from another region may respond poorly to the project’s actual heating and cooling conditions.
Useful orientation still requires appropriate glazing area, shading, room planning, insulation and air movement.
Windows provide light, outlook and ventilation but can also increase unwanted heat transfer and solar gain.
Shading that controls summer sun may also increase heating demand where it blocks useful seasonal gain.
Nominal insulation values do not fully describe performance where framing and junctions interrupt the thermal layer.
Passive ventilation should be controllable. Unintended gaps can undermine comfort when the home needs to retain or exclude heat.
Mass must be coordinated with solar access, shading and a reliable way to release stored heat.
Late assessment can leave only product upgrades available when changes to orientation, form or glazing distribution would have been more effective earlier.
Framework Boundaries
No. Passive design is a broad architectural approach to climate-responsive building performance.
Passive House is a defined international building-performance standard with specific modelling, heating, cooling, airtightness, ventilation and quality-assurance requirements.
A home can use passive-design principles without being designed or certified to the Passive House standard. Conversely, a Passive House project will usually use passive principles but must also satisfy the formal requirements of that framework.
Where an eligible NSW project uses the BASIX Passive House Standard method, the Passive House documentation supports the thermal-performance pathway. The project must still complete the other applicable BASIX assessment sections.
A passive strategy only becomes part of the approved and constructed dwelling when its relevant elements are documented clearly.
The plans, schedules and specifications may need to identify:
If the design or specification later changes, the thermal assessment should be checked before the substitute is accepted. A product that appears similar may have different thermal properties or may affect another part of the passive-design balance.
Why the BASIX Certificate must match the plans →
Frequently Asked Questions
Passive design uses the building’s orientation, form, windows, shading, insulation, thermal mass and ventilation to respond to the climate and reduce the need for artificial heating and cooling.
Passive-design decisions influence the modelled heating and cooling loads assessed in the BASIX thermal-performance section. Lower demand can also support the wider BASIX Energy result.
It can. NatHERS models the combined effect of the design and construction. A climate-responsive arrangement can reduce heating and cooling loads and improve the thermal star rating.
No. North-facing solar access can be useful in many NSW climates, but the appropriate response depends on the site, dwelling form, glazing, shading and seasonal heating and cooling requirements.
Not in every project. Window performance must be considered together with glazing area, frame type, orientation, solar gain, shading, climate and the rest of the building envelope.
No. Thermal mass is most effective where solar access, shading, insulation and ventilation allow stored heat to be useful or released when required.
No. Passive ventilation should occur through controlled openings. Airtightness addresses unwanted leakage when the dwelling is intended to be closed.
Not necessarily. Passive design aims to reduce heating and cooling demand. The need for equipment still depends on the climate, project performance, occupancy and desired operating conditions.
They are most useful when assessed during concept and design development, while orientation, form, windows and shading can still be adjusted without major redesign.
No. Passive design is a broad climate-responsive design approach. Passive House is a formal performance standard with defined modelling, airtightness, ventilation and quality-assurance requirements.
Related Knowledge
BASIX and Building Orientation in NSW →
Window Performance and BASIX →
Shading Design and BASIX in NSW →
Natural Ventilation and BASIX →
BASIX Insulation Requirements Explained →
Assessment note: Passive-design responses are climate- and project-specific. Their effect on BASIX and NatHERS outcomes depends on the complete dwelling design, assessment pathway and applicable heating and cooling requirements.
For regulatory guidance, refer to the NSW Planning Portal BASIX design principles.
Last reviewed: July 2026.
Passive Design Review
Certified Energy can review the proposed orientation, building envelope and glazing strategy and prepare coordinated BASIX and NatHERS assessment documentation for the project.
Send Your Plans for Review →