Warming and saving with windows
Benjy Simmons, from window system supplier STÄRKE, explores ways to comply with the new H1 standards in the Building Code and explains why windows are the most powerful lever to use.
“The H1 changes are about reducing heat loss across the whole building. Simply put, all of our buildings are losing heat all of the time, and it’s costing us money and electricity to keep them warm. This is impacting our collective pockets and the nation’s carbon footprint,” says Benjy.
“It’s important to state that the building envelope should be considered as a whole system, rather than individual elements and that there is more than one way to calculate the new requirements,” adds Benjy.
How do the H1 changes impact windows?
The construction R-values for windows have increased relative to the climate zone you live in. Warmer places like Auckland will see a smaller increase than colder places like Queenstown, for example. This change is gradual through to November 2023. (See Note 3 in the table in the previous feature, Building changes for a healthier New Zealand).
This means that the standard of frames and glass will improve, and there will be more discussion around window construction with terms like “thermally broken”, “PVC”, “argon filled”, “low emissivity” and “recessed” becoming part of the Kiwi vernacular.
Where is the most heat lost, and where can we save the most?
In a word – windows! As the diagram from Ministry of Business, Innovation and Employment (MBIE) shows, under the old requirements, windows are responsible for up to 50 per cent of the heat loss of a current new-build home.
Improving your window values saves you a significant amount of energy because windows are positively pouring out heat, having the lowest R-value of any element. Because this is the first step on the journey, Stärke would always recommend exceeding the minimum requirements, as this is where the biggest bang for buck is.
I’m looking at new windows. Should I spend my money on better glass or better frames?
Thinking long-term, definitely better frames. Consider PVC or timber over standard thermally broken aluminium for best results. Glass can always be upgraded over time, but frames are fixed to the building envelope, so much more difficult to upgrade. Be careful of poorly thermally broken aluminium frames as they are likely to have highly insulating glass to offset the poor insulation of the frame. This could cause the perverse outcome of actually increasing your winter heating bills, although the same glass could reduce overheating in summer.
What are your thoughts on the H1 clause in the Building Code?
We here are Stärke are very excited; it’s a long overdue revision of the standards, bringing significant change to a market that was somewhat stagnant. As admitted by the MBIE, the previous requirements had less than half the performance of internationally accepted standards.
To calculate whether your new build will meet compliance standards using the calculation or modelling methods, plans and data can be sent to Stärke, and we can do this for you.
09 279 8617 | starke.co.nz
