Sep 1

Sep 1 Warmer windows await

abode Magazine

Energy Efficiency, Expert Advice, Innovation, Services, Materials

Damien McGill of the Healthy Home Cooperation explains upcoming changes to the requirements for windows that will help make your new home more comfortable, healthier and energy efficient.

Last November, a change to insulation standards came into effect.

Known as H1, this is optional until May 2023 for building materials other than windows.

For windows, a staged change to window R-Values commences from 3 November 2022.

What is the change, and how does it relate to the windows in your new home?

Firstly, you need to understand that New Zealand has been divided up into six climate zones, pictured on the right.

Secondly, what are R-values? R-values are a measure of how much heat a material layer resists. So the R-value of a window measures how much heat is stopped by your window and therefore doesn’t escape outside. The higher the R-value, the warmer your house stays for longer.

The R-value of a standard continuous aluminium frame, double-glazed, with air-filled glass is R0.26. This isn’t great when your wall is R2.0, hence the long overdue changes.

From 3 November 2022, the R-value for windows will increase across all six zones to R0.37. Then from 1 May 2023, this will increase to R0.46 in Zones 3 and 4 and R0.5 in Zones 5 and 6. Then to R0.46 in zones 1 and 2 from 2 November 2023.

Windows are made up of two main components; the frame, made from aluminium, uPVC, or timber, and the glass. Double-glazed units have a spacer that holds the panes apart at the edges and a gap between each pane that can be filled with air or inert gas. The glass can also have a film or coating applied. All these individual items contribute to the R-value of the window.

Martin Ball of NK Windows, based in Christchurch and Cromwell, assures me that their standard uPVC double-glazed window already has an R-value of R0.39 and, in conjunction with the use of Low-E glass and argon gas filling the space between each pane, can reach R0.77. Not that I need assuring, as I’ve installed triple-glazed uPVC units in my home for R1.0+!

Rahul Jain from Metro Performance Glass explained to me that Low-E glass stands for “low emissivity”. This high-tech coating on the glass reflects heat back inside to improve its insulative properties, making the window warmer and reducing the likelihood of condensation in winter. Rahul says that it’s important to ensure argon gas is specified and that the spacer should be made of something other than aluminium, to further improve window performance. So request “warm edge” spacers in your new build.

To see high-performance windows in action and talk to the experts, join us at the Superhome Movement tours, on 25-26 September, nationwide.