Frequently asked questions on NZBC H1

An H1 report is an energy efficiency assessment used to demonstrate compliance with Clause H1 Energy Efficiency of the New Zealand Building Code. H1 reports are commonly required for: new homes architectural homes townhouses duplexes apartments some small commercial buildings The report assesses the thermal performance of the building envelope, including: insulation glazing performance thermal bridging roof, wall, and floor construction solar heat gain heating and cooling performance

Most H1 reports are completed within approximately 3–5 working days depending on project complexity and how complete the documentation is. Simple projects may be completed faster, while larger architectural homes or townhouse developments may take longer if multiple revisions are involved. Fast turnaround is one of the biggest advantages of early H1 coordination because it helps avoid consent delays and redesign pressure later in the project. For urgent projects, we can also provide same-day H1 reporting where possible. This is especially useful for projects facing consent deadlines, the build has already started and the wrong material has been installed, or situations where builders and architects need quick answers to keep the project moving.

The best H1 pathway depends on the design of the building. The H1 calculation method is generally suitable for: simpler homes standard glazing layouts conventional construction systems straightforward compliance pathways The H1 modelling method (H1/VM1) is usually better for: architectural homes townhouse developments high-glazing homes complex roof forms large window areas custom designs Customers who want to optimise build cost savings Many projects that fail under the calculation method can comply using the modelling method without requiring architectural redesign. This is especially common where clients want: less insulation larger glazing areas improved natural light cleaner architectural detailing We always get our H1 reports to comply while maintaining the original architectural intent.

To begin an H1 report, we typically require: architectural plans elevations and sections window and door schedules insulation specifications wall, roof, and floor build-ups project location or climate zone For preliminary H1 reports, early design information is often enough to begin optimisation before consent drawings are complete. We use EnergyPlus-based thermal modelling for H1 compliance reports.

The earlier H1 compliance starts, the easier and cheaper compliance usually becomes. We recommend starting during preliminary or developed design so issues can be identified before documentation is finalised. Early H1 compliance helps identify: overheating risk excessive solar gain poor glazing performance inefficient insulation strategies thermal bridging issues Late-stage H1 can sometimes force unnecessary upgrades if optimisation opportunities were missed earlier in the design process.

H1 modelling allows the building to be assessed as a complete thermal system (both heating and cooling) rather than relying only on heating, which is what the calculation method does. This creates opportunities when modelling to: reduce unnecessary insulation upgrades optimise glazing performance reduce overheating penalties minimise the need for expensive construction changes reduce reliance on high-cost thermally broken joinery in some projects Reducing overheating penalties is often one of the biggest opportunities for cost savings because overheating can drive additional insulation or glazing requirements. Careful glazing optimisation and passive performance analysis can significantly reduce compliance cost while still achieving strong thermal performance.

The biggest factors affecting H1 compliance are usually: glazing size and orientation window thermal performance (non thermally broken vs. thermally broken frames) solar heat gain coefficient (SHGC) thermal bridging in wall framing roof insulation slab edge detailing overheating risk shading design Large north & west-facing glazing areas are one of the most common causes of overheating and failed H1 modelling compliance. Modern H1 requirements now assess how a building is likely to perform in real-world conditions, including thermal bridging, glazing performance, overheating risk, and actual heat loss, rather than relying only on insulation product ratings. This leads to more comfortable, healthier, and energy-efficient homes while encouraging smarter design decisions instead of simply adding more insulation such as what was happening with the schedule method.

Not always. Many homes can comply with H1 requirements without thermally broken joinery, particularly when the glazing design, ventilation strategy, and thermal performance of the building are carefully optimised. However, thermally broken windows are generally recommended because they reduce condensation risk and improve thermal comfort compared to standard aluminium joinery. Even thermally broken joinery can still experience condensation under certain conditions, especially in homes with poor ventilation or high indoor moisture levels. A good continuous ventilation strategy is often just as important as the window frame type when managing condensation and indoor comfort.

If the design changes after the H1 report is completed, the report may need to be updated. Changes that commonly affect H1 compliance include: glazing size changes insulation changes wall construction changes orientation changes roof geometry changes floor area changes Minor changes can often be updated quickly, while larger design revisions may require the thermal model to be redesigned to match the updated plans. We regularly work directly with architects, builders, and homeowners throughout the design process and can provide as much support as needed during revisions and consent.

Yes. We regularly work with: architects architectural designers builders developers homeowners Some clients only require the final compliance report, while others want ongoing support throughout the design and consent process. We can provide as much involvement and technical support as needed during design development and council coordination.

Yes. In most cases, failed H1 compliance can be resolved without changing the architectural design. This is especially common for projects that initially fail under the schedule or calculation method due to: large glazing areas architectural complexity overheating penalties insulation trade-offs Thermal modelling often allows the design to be optimised in ways that maintain the original architecture while still achieving compliance. We regularly help projects comply where previous H1 assessments were unable to achieve compliance without redesign.

The cost of an H1 report depends on: floor area project complexity number of units glazing complexity modelling requirements level of support required Architectural homes and townhouse developments generally require more detailed modelling than simple residential projects.