Recent changes to H1 Energy Efficiency requirements in the New Zealand Building Code have sparked a wave of discussion about compliance methods.
Matthew Cutler, New Zealand Green Building Council Impact Manager – Residential, says the energy modelling route offers much greater value for both designers and homeowners.
With the removal of the schedule method, there is some promotion of the “calculation method” as the next-best and quickest route.
If you’re building or renovating, you’ll hear about three ways to show your home meets H1 requirements:
1: Schedule method
Think of this as a simple checklist. It sets minimum insulation levels for walls, roofs, floors, and windows based on your climate zone.
It’s quick and easy, but rigid — there’s no flexibility if you want to trade off one element for another. It also overcompensates in some areas such as requiring very thick roof insulation to make up for thinner wall insulation, which doesn’t always provide for a great home.
The schedule method is being removed in 2026.
This compares your design to a “reference building” using a formula. If your home performs as well or better than the reference, you comply. It allows some trade-offs (e.g., better windows for less insulation elsewhere), but it’s still based on assumptions, not real-world performance.
3: Energy modelling
This is the most detailed approach and uses software to simulate how your home will actually behave — hour by hour, season by season.
It considers your exact design, orientation, glazing, shading, and even local climate data. The result? A realistic picture of energy use, comfort, and risks such as overheating.
Benefits of modelling
Tools like ECCHO (Energy and Carbon Calculator for Homes) don’t just tick the necessary compliance box, they provide insights that can really transform the performance and comfort of a home.
Here’s why modelling is worth it:
Running cost estimates
Energy modelling simulates real-world performance, giving an indication of how much energy a home will use. This means homeowners can make informed decisions about long-term costs, rather than just relying on generic assumptions.
Greater design flexibility
Unlike rigid calculation methods, modelling allows designers to explore different combinations of materials, insulation levels, and glazing options. This flexibility can lead to smarter, more cost-effective solutions without compromising comfort or compliance.
Comfort beyond compliance
The Building Code focuses on minimum standards—but homeowners should demand more than “just compliant.” Modelling enables a focus on thermal comfort, helping to create homes that can be warm in winter and cool in summer.
Overheating risk assessment
Overheating is becoming a major issue in new homes, yet H1 and the Building Code are silent on this risk. Energy modelling can identify overheating potential early, helping designers mitigate it before construction begins.
Homeowners should demand more than a simple calculation. Energy modelling provides transparency, flexibility, and peace of mind—delivering homes that are not only compliant but comfortable, efficient, and future-ready.
In the industry and want to know more?
Check out Better by Design: Residential Energy Modelling Masterclasses being run across New Zealand throughout 2026.
Matthew Cutler