What Happens if a VURB Assessment Does Not Meet the Required Criteria?

Residential Performance Verification

An unfavourable reference building comparison does not necessarily mean a residential design must be abandoned. It means the proposed building has not yet demonstrated compliance through the selected verification method.

When a Verification Using a Reference Building (VURB) assessment does not satisfy the applicable heating or cooling load criteria, the next step is to understand the result before deciding how to respond. This may involve checking modelling inputs, reviewing the proposed specifications, considering design refinements or evaluating another appropriate compliance pathway.

In Brief

An Unfavourable VURB Result Requires Review, Not Assumptions

Under the national NCC 2022 H6V2 method, the proposed dwelling is compared with a compliant reference building using prescribed modelling conditions.

The required heating and cooling comparisons depend on the NCC climate zone. In climate zones 2 to 7, both loads must be no greater than the corresponding reference building values.

If a required comparison is not satisfied, H6V2 has not verified the proposed building's compliance with H6P1 on the assessed basis.

The appropriate response depends on the cause, the extent of the difference, the available design options and the compliance requirements applicable to the project.

Understanding the Outcome

What Does It Mean When a VURB Assessment Does Not Meet the Criteria?

An unfavourable VURB result means that one or more required thermal load comparisons have not been satisfied for the assessed design.

For example, a proposed building may have a heating load below its reference value but a cooling load above the corresponding reference value. Where both comparisons are required, the favourable heating result does not compensate for the cooling result.

The result should be distinguished from a broader conclusion that the project cannot comply with the NCC. It establishes that the current evidence does not demonstrate compliance through the relevant H6V2 comparison.

Further investigation may identify modelling issues, potential design improvements or another suitable way to demonstrate compliance. None of these outcomes should be presumed before the relevant assessment has been completed.

These are the national NCC 2022 H6V2 criteria. Jurisdictional variations must be checked separately. A combined heating-and-cooling total cannot replace an individual comparison required by the method.

Initial Technical Review

What Should Be Checked Before Changing the Design?

The first response should be to confirm that the modelling comparison accurately represents the proposed building and the required reference building.

This includes checking whether the correct drawings and specifications were used, whether common model assumptions have been applied consistently and whether the reference building satisfies the prescribed Deemed-to-Satisfy provisions.

Particular attention may be needed where architectural revisions, glazing substitutions or construction specification changes occurred during the assessment.

An input correction is not a design optimisation measure. Its purpose is to establish an accurate and defensible comparison before considering whether the proposed dwelling itself needs to change.

Potential Design Responses

What Design Changes Might Be Considered?

Where the original model is accurate but does not satisfy the required comparison, the project team may investigate changes to the proposed building's thermal characteristics.

Potential measures include alternative glazing specifications, external solar control, improvements to relevant construction assemblies or other adjustments supported by the modelling results.

The appropriate response depends on whether heating demand, cooling demand or both are contributing to the unfavourable outcome. A measure that reduces cooling demand may also affect useful winter solar gains, and the reverse may apply.

These options should be treated as matters for investigation, not guaranteed remedies. Any revised design must be reassessed against the applicable comparison and retained compliance requirements.

This table outlines practical assessment considerations. It does not prescribe a particular design remedy or guarantee a compliant outcome.

Reference Building Integrity

Can the Reference Building Be Adjusted to Improve the Comparison?

The reference building cannot be modified arbitrarily to produce a more favourable benchmark.

Under H6V2, the reference building must satisfy the relevant Deemed-to-Satisfy provisions and share prescribed characteristics with the proposed building. These include orientation, floor plan, glazing location and size, and other specified inputs.

If a genuine design revision changes a characteristic that must be common to both models, the reference building may also need to be updated. That is different from selectively weakening the benchmark to achieve a passing result.

A defensible assessment must maintain the prescribed relationship between the proposed building and its reference building throughout the modelling process.

Compliance Pathway Review

What if the Proposed Design Still Does Not Meet H6V2?

If the proposed design continues to exceed the applicable reference building load after an appropriate review, H6V2 has not demonstrated compliance on that basis.

The project team may need to consider further design changes or review whether another compliance approach is available and appropriate for the project.

The NCC provides different ways of demonstrating compliance with Performance Requirements, including Deemed-to-Satisfy Solutions and Performance Solutions assessed using appropriate Assessment Methods.

However, an unsuccessful H6V2 comparison does not itself establish compliance through another pathway. Any alternative must independently satisfy the applicable regulatory requirements and be supported by suitable evidence.

For the broader distinction between approaches, see VURB vs DTS: Understanding the Reference Building Pathway.

Assessment Documentation

How Should the Revised Assessment Be Documented?

Where modelling inputs or design specifications are revised, the technical record should make clear which design version has been assessed and which assumptions support the final comparison.

This may include revised architectural drawings, updated glazing or construction schedules, model input records and the resulting heating and cooling load comparisons.

A previous unsuccessful result should not be presented as evidence of compliance. Equally, a revised result should not be relied upon until the relevant criteria and additional requirements have been checked.

The extent of reporting and any required approval documentation depend on the applicable Performance Solution process, project stage and regulatory authority.

Practical Next Steps

A Structured Response to an Unfavourable VURB Result

01 — Confirm the Applicable Criterion

Identify which heating or cooling comparison is required for the relevant climate zone and which criterion has not been met.

02 — Validate the Modelling Basis

Review the calculation method, common assumptions, reference building construction and current project inputs.

03 — Investigate the Thermal Drivers

Determine which aspects of the proposed building contribute to the unfavourable comparison.

04 — Evaluate Appropriate Options

Consider supportable design changes or another applicable compliance pathway without assuming either will achieve compliance.

05 — Reassess and Document the Outcome

Undertake the necessary reassessment and ensure the final technical evidence aligns with the design being submitted or constructed.

This is a practical review framework, not a separately prescribed five-step NCC procedure.

Residential Performance Review

Need to Understand an Unfavourable VURB Assessment Result?

Share your project location, current drawings and available assessment results. Certified Energy can review the applicable compliance requirements and advise on appropriate technical next steps for your residential project.