Existing homes present conditions that do not arise in the same way on new buildings. Orientation, structural junctions, floor levels, roof geometry, boundaries, heritage fabric and concealed construction may already be fixed before the retrofit begins.

EnerPHit accounts for these constraints while retaining a defined pathway for energy demand, envelope performance, airtightness, ventilation, documentation and construction verification. It should not be used as a general label for any renovation that adds insulation or improves windows.

This guide focuses specifically on the retrofit pathway. For the wider standard, five principles, Australian climate application and PHPP framework, see the Passive House in Australia Knowledge Hub.

Double glazing is frequently presented as a direct route to a higher NatHERS star rating. It can be an effective improvement, particularly where heat transfer through the windows is limiting the dwelling’s thermal performance. It is not, however, a guaranteed or identical solution for every project.

NatHERS does not assess the number of glass panes in isolation. The model uses the thermal properties of the complete window system, including the glass, frame, seals and other relevant components. Window size, location, orientation and shading also influence how that system performs within the dwelling.

This guide focuses specifically on when double glazing may improve the model, what the window performance values mean and which information should be coordinated with the assessor and supplier.

For the broader relationship between climate, orientation, shading, insulation and building form, see How to Design a 7 Star NatHERS Home.

The cost of reaching a 7 Star NatHERS target varies between projects. Some designs may require only focused refinements, while others may need wider changes to glazing, shading, insulation, construction or building form.

The difference is rarely explained by one product alone. A high-cost upgrade may provide limited improvement when it does not address the part of the dwelling creating the dominant heating or cooling load. Conversely, several smaller changes may produce a stronger result without unnecessarily increasing the specification across the entire home.

This guide focuses specifically on how project teams can prioritise expenditure when working towards the target. For the broader relationship between climate, orientation, glazing, shading and construction, see How to Design a 7 Star NatHERS Home.

For guidance on what the 7 Star benchmark means and when it may apply, see the 7 Star NatHERS requirements guide.

Green home loans are intended to support the purchase, construction or improvement of homes that satisfy defined environmental or energy-performance criteria. Depending on the product, the lender may offer a pricing benefit, additional finance for upgrades or another incentive.

NatHERS can provide recognised technical evidence about a new home. Its thermal star rating describes the modelled heating and cooling performance of the dwelling fabric, while a separate Whole of Home rating may record the broader modelled energy performance of household systems, solar generation and battery storage.

Whether either result is accepted for a particular green loan remains a lender decision. Applicants should confirm the lender’s current eligibility criteria before relying on a target rating, specification or certificate.

Indoor Environment Quality, commonly shortened to IEQ, is one of the categories assessed within BESS Buildings. The category does not provide a general rating of whether a building is healthy or comfortable. Instead, it applies defined credits to particular development types and requires project information or evidence to support the responses entered into the assessment.

The applicable IEQ credits change according to the project profile. An apartment development may be assessed for daylight access, natural ventilation, cross-flow ventilation and particular thermal-comfort measures. A non-residential development may instead require daylight, ventilation, shading, ceiling-fan or air-quality evidence relevant to its regular-use areas.

This guide explains how IEQ operates within BESS and what information may be required to substantiate the assessment. For the complete planning, scoring and report pathway, see the BESS Knowledge Hub.