H1 Updates and What They Mean
The New Zealand Building Code’s H1 clause — Energy Efficiency — has been progressively strengthened over recent years, requiring builders to achieve higher levels of thermal insulation and energy performance in new buildings. The updated H1 requirements represent the most significant change to residential construction specifications in many years, and understanding what they require — and how to achieve compliance cost-effectively — is important for every residential builder.
The key change is the requirement for higher R-values in roof, wall, and floor insulation across all climate zones. New Zealand is divided into six climate zones, ranging from the warm north (Zone 1) to the cold South Island interior (Zone 6). Higher insulation requirements apply in all zones, but the step-change is most significant in the middle and southern zones where previous requirements were lowest relative to the climate.
Roof Insulation
Ceiling insulation requirements have increased substantially under the updated H1. Achieving the required R-values in standard ceiling spaces typically requires thicker insulation batts or a combination of batts and reflective sarking. For builders working in attic spaces with limited depth — particularly in renovation work — achieving the required R-values while maintaining ventilation and avoiding thermal bridges requires careful detailing.
Wall Insulation
Wall insulation requirements have increased significantly, and the standard 90mm framing with R2.2 glasswool that was the previous norm does not meet the new requirements in most climate zones. Builders have adopted various approaches to achieve compliance: higher-performance insulation products, increased framing depth (140mm studs), exterior rigid insulation layers (adding depth to the wall build-up), and advanced framing techniques that reduce thermal bridging through timber framing.
Windows and Glazing
Windows are the biggest source of heat loss in most buildings, and H1 compliance for windows focuses on the whole-of-window thermal performance (U-value) rather than just the glass performance. Double glazing has become standard in new residential construction, and triple glazing is increasingly specified in colder zones. The framing material and edge spacer in double-glazed units significantly affects the whole-window performance, so specification decisions need to look beyond the glass alone.