HERE magazine have produced their first ever Guide to Building which focuses on the building process, detailing how a few of their favourite houses came to be and a few things on their want list. They also delve into some current issues with industry experts, including a Q&A with our very own senior design engineer.

Read the Q&A here or download the full guide below

Interview by Simon Farrell-Green. This piece was originally published in HERE magazine.

Last November, the first of a series of major changes to the building code came in: over the course of 2023, new buildings in every part of the country will be required to meet higher standards of thermal performance. In short, buildings in more temperate parts of the country are now required to perform better than the buildings in colder regions did under the old code – and those in cooler regions are now subject to considerably more stringent standards than before.

The impact of this cannot be overstated. For decades, New Zealand homes have been notoriously cold. Now, they’re required to perform at an international standard, which will make them warmer (or cooler), healthier and more energy efficient. The code ensures all that by requiring each aspect of a building to perform better – and windows are one of the most crucial elements in keeping a building warm. 

For homeowners and architects, it’s now not enough to just opt for double-glazing; a sophisticated suite of technology is required to make sure you comply with the code. So, we reached out to Dave Burggraaf, senior design engineer at window systems supplier APL Window Solutions – for a deep dive into the new rules.

Here: So what’s actually changing?
Dave Burggraaf: The New Zealand Building Code (NZBC) clause H1 provides for the efficient use of energy and sets physical conditions for energy performance of certain buildings. The changes to H1 that affect glazing are an increase to the minimum R value of the entire window or door unit. The R value is a measure of how well the building element (a window, for example) resists the conductive flow of heat from one side to the other. In winter, the heat wants to escape and in summer it wants to get in. A higher R value product provides more resistance to this heat flow.

H: How much more efficient do our homes have to be?
DB: The previous code set a minimum level of R0.26 and slightly higher for the colder parts of the country. The new regulations apply to all new homes, and require the minimum R values to be R0.46 in the more temperate areas and R0.50 in the colder areas. So we see a very large jump in requirements for specialty glazing and thermally improved window and door frames.

H: Why have the regulations changed?
DB: The changes are part of the larger initiative to get New Zealand to carbon neutral by 2050. There have been changes to NZBC H1 before, and we see future changes coming sooner and with bigger steps on the way to achieving carbon neutral.

H: Where does it place us now in global terms?
DB: The recent changes to H1 place New Zealand about in line with international standards. This is an impressive lift in performance, keeping in mind that we don’t see the extreme hot or cold of other countries.

H: Where do I start to work out what level of performance I’m going to need?
DB: Start with the NZBC clause H1/AS1: if your building is less than 300 square metres (which is the majority of new houses) and glazing is less than 30 percent of the total wall area, there are tables within the acceptable solution that set out minimum R values depending on where you live. If your building is larger than 300 square metres or glazing takes up more than 30 percent of the wall area, there are other ways to establish minimum performance levels, such as calculating or modelling where thermal performance levels are averaged over all joinery units.

We’ve developed an online tool that will tell you which zone you fall into. Climate zones 1 to 4 require a minimum of R0.46 and climate zones 5 and 6 a minimum of R0.50. There are special conditions for opaque doors, and skylights require a higher R value again.

H: What do we stand to gain?
DB: Any thermal-performance improvements to the building envelope help to reduce the energy required for heating and cooling, and the ThermalHeart+ products will certainly contribute to these savings.

H: How have you met those new requirements?
DB: We have produced larger platform frames capable of taking much thicker glazing units – up to triple glazing if needed. Within the window profiles, we have incorporated thermal isolator strips which prevent energy transfer across the frames, resulting in higher R values.

Previously, window performance has emphasised glass, or the frame: with ThermalHeart+ all the parts of the window including glass and frame work as a high-performance unit. The new system adds multiple innovations to achieve higher weather performance, better acoustics, improved airtightness, longer-term durability of materials and enhanced structural strength.

A key component to improving energy efficiency is airtightness. The ThermalHEART joinery ranges adopt new methods of sash and panel sealing to ensure the tightest fit for sashes and panels while remaining easily operable. Along with lower energy bills, benefits include enhanced internal surface temperatures (especially with the Centrafix installation option). Finally, The AGP System for glazing helps limit overheating in summer and retains heat in winter – this reduces the energy needed for heating and cooling.

H: What do they actually do?
DB: It’s quite simple: the combination of thermally improved frames and insulated glass units with low-emissivity coating; and a very efficient spacer system with the gap between panes filled with argon gas gets us across the compliance line easily – with the capacity to achieve higher R values if required. With Centrafix, we can do even better.

We’ve configured our new three-tier ThermalHEART product range to satisfy any code requirement – up to and including a Passive House variant. This demonstrates the breadth of capability of the new systems now and into the future.