NatHERS Compliance
Renovations, alterations and additions can sometimes trigger residential energy compliance requirements. Whether NatHERS is needed depends on the scope of work, the state or territory, the approval pathway and how much of the home is being changed.
Not every renovation requires a NatHERS assessment. However, some alterations and additions may need thermal performance assessment where new work, changed building fabric or approval requirements trigger residential energy compliance. The requirement should be checked early, especially when the renovation changes glazing, insulation, roof form, floor area, conditioned spaces or the external envelope of the home.
NatHERS is most commonly associated with new homes, townhouses and apartments. In those projects, the whole dwelling is usually being assessed as part of the residential energy compliance pathway.
Renovations are more variable. One project may only involve internal changes. Another may add a new wing, change the roof, replace large areas of glazing or alter the thermal envelope of the home. Because the scope can vary so much, the energy compliance pathway can also vary.
This is why renovation projects should be checked rather than assumed. A small cosmetic update is very different from a major alteration that changes how the home performs thermally.
A renovation may need thermal performance assessment when it affects the parts of the home that separate indoor conditions from outdoor conditions. This includes walls, roofs, ceilings, floors, windows, doors, insulation and other elements of the building fabric.
An addition may also create new conditioned floor area that needs to comply with current requirements. In some cases, the new work may need to meet a particular energy standard even if the existing part of the home was approved under older rules.
The exact requirement depends on the approval pathway, jurisdiction and project scope. A certifier, designer or energy consultant can help confirm what applies before the documentation is finalised.
Renovation requirements are usually scope dependent.
The more a project changes the building fabric or creates new conditioned space, the more important it is to check the thermal performance pathway early.
Alterations and additions are often where NatHERS questions arise. A new bedroom wing, upper floor addition, rear extension or major reconfiguration can change the thermal behaviour of the home.
If the addition includes new external walls, roofing, glazing, floors and conditioned rooms, those parts of the project may need to demonstrate compliance with current energy requirements. Depending on the jurisdiction and pathway, NatHERS may be one way to support that assessment.
The existing home can also complicate the process. Older construction may have lower insulation levels, different glazing and more air leakage than a new home. The compliance approach needs to account for the actual project context.
Renovations often involve new windows, larger openings, sliding doors or altered façades. These changes can affect thermal performance because glazing has a strong influence on heat gain, heat loss and comfort.
If a renovation adds large areas of unshaded glass, especially on difficult orientations, it may increase cooling demand. If it uses low performance glazing in a cooler climate, it may increase heat loss. The right response depends on the home, climate and room use.
For more detail, see our guide to how window design affects NatHERS ratings.
• New conditioned floor area
• New or altered external walls
• New roof forms, raked ceilings or upper level additions
• Larger windows, glazed doors or façade changes
• Floor construction changes, suspended floors or floors over garages
• Insulation, shading or roof colour changes linked to compliance
Roof and ceiling changes can also affect whether a renovation needs thermal performance review. A new roof, raised ceiling, raked ceiling, attic conversion or upper level addition may change how heat enters or leaves the home.
These changes can make insulation depth, roof colour, ceiling construction and air sealing more important. A raked ceiling, for example, may have less room for insulation than a conventional ceiling under a roof space.
For more detail, see our guide to ceiling insulation and NatHERS outcomes.
Many renovation questions come down to what is being added or changed. A new conditioned room may be treated differently from an unconditioned garage, deck, porch or storage area.
Where the project adds rooms that will be heated or cooled, the new space may need to be assessed against current energy requirements. The boundary between conditioned and unconditioned spaces should be clear in the documentation.
This can be especially important where a renovation converts garages, verandahs, attics or undercroft areas into habitable rooms.
An existing home is not automatically exempt from energy requirements just because it was built under older rules.
New work may still need to satisfy current requirements, depending on the project scope and approval pathway.
In NSW, many residential renovation and addition projects need to consider BASIX. Depending on the project, NatHERS modelling may be relevant to the thermal performance part of the pathway.
This can be confusing because BASIX and NatHERS are connected but not identical. BASIX is the NSW sustainability certificate pathway. NatHERS is a thermal performance assessment method that may support part of that pathway.
For a clearer comparison, see our guide to NatHERS vs BASIX.
A renovation can involve two related but different conversations. One is compliance for the proposed building work. The other is the broader performance of the existing home.
NatHERS for new homes and new work is generally about demonstrating thermal performance for the design being approved. Existing home performance may involve different assessment types, depending on whether the goal is compliance, advice, retrofit planning or understanding comfort issues.
For renovation projects, it is useful to separate the compliance requirement from the wider opportunity to improve comfort, insulation, glazing, draught control and heating or cooling efficiency.
Where NatHERS or thermal modelling is relevant, it can help identify how design decisions affect heating and cooling demand. This can be valuable in renovations because existing homes often have known comfort issues that the new work may either improve or worsen.
For example, a renovation may add better insulation and shading, but also introduce large glazing areas. Modelling can help test whether the overall thermal pathway is improving or whether new performance issues are being created.
The best renovation outcomes usually come from treating energy compliance and comfort as part of the design process, not as a final check after the drawings are complete.
• Existing and proposed plans
• Scope of works and approval pathway
• New conditioned floor area
• Existing and proposed construction details
• Window, glazing, insulation and shading information
• Any BASIX, NCC, council or certifier requirements already identified
Renovations should be checked early, especially if the project adds habitable rooms, changes the roof or glazing, alters the external envelope or requires formal approval. Early review can help confirm whether NatHERS, BASIX or another energy pathway is likely to apply.
If energy compliance is left until the end, the project may need late design changes. This can affect window selections, insulation specifications, roof colour, shading details or construction documentation.
Early review gives the project team more time to resolve the pathway calmly and keep the design, approval documents and construction details aligned.
If NatHERS is required for a renovation or addition, the assessment may help demonstrate that the new work or relevant parts of the project meet the applicable thermal performance pathway. The exact scope should be confirmed for the project.
For NSW projects, this may connect with BASIX. For broader residential energy requirements, it may also connect with Whole of Home where applicable. For new homes and some major new work, the 7 Star Rating pathway may also be relevant.
Because renovations involve existing conditions, the correct pathway should always be confirmed against the actual scope and jurisdiction rather than assumed from a new home project.
Australian renovations often involve older homes with lower insulation levels, leaky construction, single glazing, dark roofs or layouts that were not designed around passive comfort. A renovation is an opportunity to improve these conditions, not just add more space.
The most effective changes are usually those that respond to the specific climate and home. A cool climate renovation may focus on heat retention, glazing and draught control. A warm climate renovation may focus more on shading, ventilation and reducing heat gain.
The aim is to make the new work comfortable, compliant and coherent with the existing home, rather than treating energy performance as an afterthought.
Certified Energy provides NatHERS assessments and residential energy compliance support for homes, townhouses, apartments, alterations and additions across Australia. Our team can review the project scope and documentation to help identify whether NatHERS is likely to be part of the required pathway.
Where relevant, we can help connect the renovation pathway with related requirements such as NatHERS, BASIX, 7 Star Rating and Whole of Home.
For the broader assessment framework, visit our NatHERS Knowledge Hub.
Some renovations, alterations or additions may require NatHERS or another thermal performance assessment, depending on the scope of work, jurisdiction and approval pathway.
Do all renovations need NatHERS?No. Not all renovations need a NatHERS assessment. The requirement depends on the project type, extent of new work, state or territory rules and the compliance pathway being used.
Can an addition need NatHERS even if the existing home is old?Yes. New work may need to satisfy current energy requirements even if the existing home was built under older rules. The exact pathway depends on the project scope and jurisdiction.
Is NatHERS the same as a renovation energy audit?No. NatHERS is usually used for thermal performance modelling in a compliance context. A renovation energy audit or existing home performance review may have a different purpose and assessment method.
When should NatHERS be checked for a renovation?NatHERS should be checked early for renovations, especially where the project changes the building fabric, glazing, floor area, roof form, insulation or conditioned spaces.