The prescriptive pathway for energy efficiency is on its way out for buildings in New Zealand. The clock is ticking (and nearly done!) on a one-year transition period to phase out the H1 Schedule Method. By November 2026, teams must be ready to demonstrate how a building performs as a total system rather than a collection of parts.
The removal of the Schedule Method reflects a broader issue raised during public consultation – prescriptive compliance does not always lead to good building performance.
For many projects, this is a challenge, particularly where H1 compliance has been addressed late as part of building consent. Without a simple prescriptive pathway, teams now need to demonstrate how the building performs as a whole system. This shift aims to balance upfront construction costs with long-term efficiency, introducing more consistent measurement rules and updated modelling methods to better reflect modern building practices.
Moving beyond prescriptive design
The old approach applied fixed R-values to individual elements – for example walls, roofs and floors – regardless of building orientation, glazing design or local context beyond the climate zone the building was in. While simple, it often led to:
- overly conservative or expensive material selections
- limited architectural flexibility
- poor consideration of solar gains and overheating risk.
Previously compliant buildings have demonstrated that meeting insulation requirements alone does not guarantee performance. In some cases, it has contributed to overheating, particularly where large north-facing glazing allows excessive solar radiation into a highly insulated envelope, trapping heat.
The new whole-building approach
The updated H1/AS1-2 and H1/VM1-2 frameworks shift toward greater flexibility in design to demonstrate compliance by the mandatory use of either the Calculation or Modelling Methods. The Calculation Method provides a simplified system-level assessment, while the Modelling Method (H1/VM1 & VM2) enables more detailed simulation of real building behaviour.
While the Calculation Method still largely ignores the context of the building – i.e. dynamic solar exposure or local shading from the building form – it does provide flexibility for the design team to focus insulation in areas that would lend itself to better buildability.
The best method to demonstrating compliance with the energy efficiency clause H1 would be to use the Modelling Method. This is also the only option for compliance if the building design contains curtain walls.
Importantly, the modelling pathway compares designs against:
- a base case aligned with the old Schedule Method, such as R6 roof insulation in Climate Zone 5 (e.g. Christchurch)
- defined solar heat gain coefficient (SHGC) requirements for glazing.
This creates an opportunity: if the design responds well to solar orientation and building form, it can outperform the base case and demonstrate compliance more efficiently.
This aligns with the Ministry of Business, Innovation and Employment (MBIE)’s intent to move toward performance-based design where energy efficiency is assessed on how buildings actually behave.
A new approach to compliance
A sustainability consultant can guide you through the following:
- Will the use of the calculation or modelling method increase design time and cost?
- How do we avoid overdesign or unnecessary material spend?
- How do we manage overheating risk while still meeting insulation targets?
There is also delivery risk. Without a clear strategy, projects may default to conservative design to play it safe or face late-stage redesign if the building does not meet H1 requirements at consent.
Practical steps to compliance
At NDY, we favour the use of the modelling method as we strongly advocate the use of digital, data-driven tools to provide the best results for our clients. Here’s our step-by-step pathway:
1. Site-specific climate response
We model the building in its actual location, from Northland’s humidity to Otago’s colder climate, ensuring the design responds to both heating and cooling demands using NIWA’s latest weather file.
We also ask our clients if they’d like us to use NIWA’s latest weather files which include future prediction files, allowing us to accommodate worst-case hot summer days, to really stress-test a design. This is not part of H1 but it enables us to use the generated model beyond compliance and offer greater value.
2. Solar orientation and shading
We assess how solar radiation interacts with building form and glazing. This allows us to maximise passive heating in winter and reduce overheating risk in summer.
Orientation and building form become active contributors to compliance.
3. Cost vs performance trade-offs
We move away from rigid R-values to achieve the same performance outcome by test combinations of building elements, including:
- increasing insulation in key areas whilst allowing other areas that have buildability constraints to be reduced
- adjusting glazing performance and SHGC.
This identifies the most cost-effective solutions while still meeting the overall energy targets.
4. Thermal bridging accuracy
Clause H1 puts a significant emphasis on the consideration of thermal bridging when calculating the overall thermal resistance of the building thermal envelope. Often, the presence of a thermal bridge within a wall – due to construction detail – can devalue large amounts of insulation, making the design costly and potentially problematic as a condensation risk.
We understand where these crunch points are during a design and help aid the design team towards a compliant wall construction without sacrificing insulation. We account for real construction conditions, to ensure the design performs as intended.
5. Leveraging the base case
Because the reference building reflects the old schedule, there’s a clear pathway to demonstrate compliance through better design. Solar gains, glazing and form can be used strategically to outperform the baseline using the modelling method.
Key differences between compliance methods
| Schedule method (being phased out) | Calculation method | Modelling method |
|---|---|---|
| Set R-value minimums that must be achieved by the respective building thermal envelope element, i.e. R6 for the roof | Flexibility on what R-values could be targeted per respective building thermal envelope if traded off with another element, i.e. less insulation in the walls but more in the roof | Flexibility on what R-values could be targeted per respective building thermal envelope, considering ALL elements of the design of the building.
Some trade off may occur, depending on exposure to sun or building use, i.e. less insulation may be needed overall if glazing and shading were optimised. |
| No consideration of building context (other than climate zone) | No consideration of building context (other than climate zone) | Considers building context |
| No consideration of external or internal shading | Small consideration of shading with glazing solar admittance but no dynamic consideration of changes throughout a day or year | Considers shading and full solar exposure throughout the year |
| No consideration of weather | No consideration of weather | Uses latest NIWA weather files of typical ambient conditions for the building location. |
| No consideration of thermal storage / mass | No consideration of thermal storage / mass | Can include passive techniques such as thermal mass (e.g. concrete) to reduce heating and cooling requirements, potentially reducing the need for insulation or better performing elements. |
Applying this pathway on your project
For a typical project, we would integrate modelling at concept stage and throughout the design process to reduce risk and avoid redesign at consent.
1. Review the concept design
- Assess building form, orientation, glazing and envelope strategy against H1 requirements.
- Develop a baseline model.
- Compare the proposed design against the H1 reference building to understand the compliance gap.
2. Iterate targeted options
- Test adjustments to insulation levels, glazing performance and shading strategies to optimise both performance and cost.
On a recent project, this approach allowed us to increase roof insulation and refine glazing performance, reducing wall insulation requirements while still achieving compliance. This avoided unnecessary material cost while improving thermal .
3. Confirm compliance pathway
Document modelling outcomes to support building consent under H1/VM1 or VM2.
4. Support delivery
Work alongside the design and construction team to ensure the built outcome aligns with model assumptions.
Let’s deliver better performing buildings
The shift away from the Schedule Method is a move toward better-performing buildings. By integrating modelling early, projects can achieve a warmer, drier and more energy-efficient outcome while maintaining buildability and controlling cost.
