What Changed in H1
MBIE’s 2022 update to the H1 energy efficiency provisions of the Building Code raised minimum window performance requirements substantially across all New Zealand climate zones. In the Northern Region, the minimum window R-value increased from R-0.37 to R-0.46. Southern zones face even stricter requirements. Modelling suggests the new standards, applied across a complete building envelope, can reduce heating energy requirements by up to 40 percent compared to the previous minimum standard.
For most new residential and commercial construction, meeting these requirements means using thermally broken window systems. Standard aluminium frames — where the outer and inner aluminium sections are connected directly — conduct heat rapidly through the frame, creating cold spots that trigger condensation and undermine the overall thermal performance of the building envelope regardless of the glass unit’s performance.
How Thermal Breaking Works
A thermally broken aluminium frame incorporates a polyamide (nylon) strip or other low-conductivity material between the outer and inner aluminium sections, breaking the continuous metallic path through which heat would otherwise transfer. The result is a frame that maintains the structural properties and workability of aluminium while dramatically reducing its thermal conductivity.
The practical consequence is a warmer internal frame surface — one that stays above the dew point under most winter conditions, preventing the condensation that encourages mould growth on and around window frames. Combined with a high-performance double-glazed unit, a thermally broken frame delivers a window assembly that contributes meaningfully to the building’s thermal envelope rather than creating a weak point in it.
The Market Challenge
Many builders continue to default to standard aluminium windows on cost and familiarity grounds. The upfront cost premium for thermally broken systems is real, though it has narrowed as local manufacturers have expanded production. The long-term case — lower heating bills, reduced condensation and mould risk, improved occupant comfort, and demonstrated compliance with current code requirements — is strong, but it requires someone in the procurement chain to make it to the client.
Builders who specify thermally broken windows without being asked are providing value beyond compliance — they are delivering a building that performs better, causes fewer problems, and supports the client’s long-term satisfaction. In a market where defect claims and follow-up work are significant costs, the specification choice pays for itself in ways that do not show up on the material cost comparison.
Supply Chain Status
New Zealand manufacturers are increasing thermally broken frame production, but regional availability varies. Lead times for some profiles remain extended, particularly in smaller cities and rural markets where the supplier network is thinner. Building programmes that require thermally broken windows should factor procurement lead times into their scheduling rather than treating window specification as a detail that can be resolved at the last moment before installation.
