The New Zealand Building Code now mandates thermally broken joinery in new homes. But what does this mean, and what are the benefits?
Double glazing has long been used to regulate indoor temperatures by capturing a layer of air or argon gas between two glass panes, interrupting heat transfer. A “thermal break” involves separating conductive materials like glass or aluminium with poor heat conductors to reduce this transfer.
A “thermally broken window” has a low-conductivity material creating a break between the interior and exterior aluminium frame and between the panes of glass. This means the aluminium frame is split into two parts, preventing one side from touching the other. Thermally broken windows offer several benefits.
Windows are a significant source of energy loss, with traditional aluminium frames allowing eight times more energy to escape compared to the same insulated wall area. Thermally broken frames with high-performance glass can achieve an R-value of up to 0.8, while traditional, non-thermally broken joinery offers an R-value of up to R0.33.
In winter, traditional aluminium window frames match the outside temperature, creating drafts when warm indoor air meets the cold frame. In contrast, thermally broken frames are less affected by the exterior temperature, staying warmer and improving temperature stability. In summer, thermally broken frames also work to minimise heat transfer into the room. Thermally broken frames with high-performance double glazing can achieve an R-value of up to 0.8, much higher than standard double-glazed frames. They also help reduce condensation by maintaining a similar temperature to the room interior, minimising moisture build-up.
Learn more about thermally broken joinery at wganz.org.nz
In winter, traditional aluminium window frames match the outside temperature, creating drafts when warm indoor air meets the cold frame. In contrast, thermally broken frames are less affected by the exterior temperature, staying warmer and improving temperature stability.
In summer, thermally broken frames also work to minimise heat transfer into the room. Thermally broken frames with high-performance double glazing can achieve an R value of up to 0.8, much higher than standard double glazed frames.
