NZIA publishes their results of Energy Modelling Practices for Design and Compliance Survey
“Unlocking Better Building Performance and Healthier Homes
We are excited to release the results of the Energy Modelling Practices for Design and Compliance Survey. Thank you to all those that participated and special thanks to Joe Lythe and Elrond Burrell for their contributions!
As Aotearoa moves toward a net-zero carbon future by 2050 energy modelling remains underutilised despite its potential. Most building projects still use prescriptive methods or basic calculations rather than advanced modelling. While Clause H1 permits energy performance verification, it’s not mandatory for all projects. This creates a gap where compliance-focused approaches dominate over performance optimisation.
H1 compliance modelling tends to use simplified assumptions that don’t match real-world energy use patterns, leading to buildings that technically meet code but underperform operationally. Predictive energy modelling, by contrast, enables better design decisions – optimising insulation, allowing for strategic ventilation system design, and material selection balancing embodied carbon and thermal performance to reduce energy bills, cost, and improve comfort. These capabilities directly support both energy savings and improved occupant comfort, making it crucial for achieving climate goals while maintaining living standards.
In Australia, around 90% of new homes are assessed using energy modelling under the Nationwide House Energy Rating Scheme (NatHERS), which ensures minimum thermal performance standards. Similarly, the UK mandates energy modelling for all new residential developments, with the upcoming Home Energy Model set to further improve accuracy.
Concerns about cost are often overstated. A study in Australia found that increasing energy ratings from 5.9 to 7.1 stars added just $37 on average to build costs. Meanwhile, the long-term savings in energy bills and material efficiency far outweigh the initial investment.
The results reveal that traditional compliance methods still dominate, with the Calculation Method being the most used pathway. Adoption of energy modelling in the design process remains limited, with just 38% of respondents incorporating it – often relying on external consultants rather than in-house expertise. A significant skills gap persists. Additionally, performance risk assessments – such as evaluating thermal bridging, heat loss, and moisture risk – are rarely conducted, despite their importance for building durability and occupant health.
The Institute has urged the government to modernise design standards – phasing out outdated methods, introducing predictive energy modelling for townhouses as a starting point, and introducing absolute performance targets. Upskilling architects are key to success. Energy modelling isn’t only about compliance, it is about building better, healthier, and more resilient homes for the future.”
