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.

Windows are one of the most influential parts of a residential thermal-performance assessment. They provide daylight, views and ventilation, but they can also transfer heat more readily than insulated walls, roofs and floors.

Within BASIX and NatHERS, window performance is determined by more than whether the glass is single or double glazed. The complete window system—including the frame, glass, opening type, size, orientation and shading—affects the modelled heating and cooling demand of the dwelling.

The final assessment may establish maximum U-values, acceptable Solar Heat Gain Coefficient ranges and dwelling-specific window requirements. Those values must then be coordinated with the architectural plans, window schedule, supplier information and installed products.

Thermal performance is the part of BASIX that assesses how much artificial heating and cooling a proposed dwelling is expected to require. It considers how the building envelope responds to the local climate before the efficiency of the installed heating or cooling equipment is taken into account.

The result is influenced by the dwelling geometry, orientation, glazing, shading, insulation, construction systems and exposure to external conditions. BASIX compares the estimated or simulated heating and cooling loads with the maximum loads allowed for the project.

A project must satisfy the applicable heating and cooling requirements using an accepted assessment method. Depending on the dwelling and project pathway, this may be the BASIX DIY Method, NatHERS Simulation Method or Passive House Standard method.

BASIX targets are the minimum performance outcomes a residential project must satisfy for water use, operational energy and thermal performance in New South Wales.

The term “target” is widely used by project teams, although NSW planning requirements formally refer to BASIX standards. The BASIX Tool compares the proposed development against the applicable standards and produces separate water and energy scores, together with heating and cooling performance results.

There is no single statewide BASIX score that applies to every project. The required outcomes vary according to factors such as location, dwelling type and development configuration. Each applicable assessment area must satisfy its own requirement before the BASIX Certificate can be generated.