You may have heard about the highly anticipated updates to H1, a segment of the building code that focuses on energy efficiency. These updates primarily address insulation, windows, and other related details. H1 has long lagged behind international standards, leaving New Zealanders in perilously subpar housing conditions that have been proven to contribute to health issues. The minimum requirements set by the building code have been insufficient.
Architects, such as those affiliated with sips.network, are actively exploring various approaches to construct better homes. We rely on our expertise and strive to discover superior alternatives. Sharing knowledge is a key aspect of our efforts to continuously enhance the prevailing standards. However, this task has not been without challenges.
The stringent E2 section of the building code, which pertains to weather tightness and external moisture, dictates that windows be installed outside the building envelope. While windows play a critical role in insulation, being positioned outside the insulation layer significantly hampers their effectiveness.
For many years, it was considered a standard practice to install windows in this manner. I have included an image that illustrates the head detail of the window, with an arrow indicating the flow of heat.
The reason behind these installation details stems from the history of "leaky buildings." To address the issue of windows leaking, the building code mandated their placement outside the building envelope, which unfortunately prevents them from effectively retaining warmth. While it may sound complicated, it really isn't. Over the years, we have designed specific flashing details that allowed us to bring the window inward, aligning it with the insulation. However, as this approach becomes more challenging to implement and since each window performs differently, there can be resistance from both regulatory authorities and builders.
For the past decade, I have been advocating that this problem, unique to New Zealand's method of issuing building consents, needs to be solved by window manufacturers themselves. It should not be solely the responsibility of the building code, designers, or councils. All stakeholders should be able to rely on the product and its manufacturer to provide a dependable solution.
Fortunately, we have started to witness a gradual shift in this perspective. A few manufacturers have acknowledged the issue, and recent changes in the H1 regulations are likely to shake things up further.
Today, it is easier than ever to make the right choice and build windows that effectively fulfill their purpose. However, we are currently limited to only a few specific products.
Cladding like RK Intereset has come up with its specific set of details, flashings to work with any windows and enable fully recessed windows https://www.cedarscreen.co.nz/interset/overview/
There are another couple of cladding solutions that come close but not quite how these need to be. Some I don't think even know that they do. Like Specilised AAC cladding due to the special flashing system, actually gets windows in-line with the cavity, which is about 20-30mm deeper than most other claddings. With some deaper joinery you could almost get it right.
There is also Metalcraft with their so called recessed window details. Again much better, but not quite perfect.
In terms of thermal performance, PVC and timber windows typically outperform aluminum thermally broken windows. This is why they are generally easier to recess properly into the wall, aligning them with the insulation. However, due to the increasingly challenging consenting process, not all manufacturers possess the necessary testing and certification to substantiate their construction methods. As a result, various issues arise throughout the consent and building process, causing complications and delays.
One that solved recessed UPVC windows and has certified details is Stärke Ambiance Inline windows: https://starke.co.nz/suites/starke-ambiance-upvc-window/
Another good option is basically an independent flashing system, that allaws the use of most claddings and most windows, but with their flashing system windows are nicely recessed in the wall. Again proper details and certification make Eurotect Flashings a good option.
Personally I have been waiting to see something from the mainstream aluminum joinery. Massive industry, lots of products and recently thermally broken windows becoming more and more popular. But if this termal break sits so far outside the wall, that there is cold air on both sides of the break, it really doesn't make much sence to have the thermal break in the first place.
And finally we seam to have some movement in this area as well. APL came up with what looks like an adjustment to their thermally broken framing, that also includes deep flanges on all corners, enabling window to be recessed further into the wall, while flanges still divert water out and over the cladding.
It seams like an incredibly long wait but after years of hard work, lots of talking and pushing this industry to do better... we just might have some results heading our way.
This might just be the best thing since SIPs in NZ😁. Becouse if you know how to properly use SIPs, insulate foundation and now recess your windows... well... you just might have your building envelope sorted. Sounds easy but it took a long time and a lot of hard work!
As always, please comment below if you know of other options or if you have any experience with these products listed above. Nothing like sharing the knowledge with like minded comunity.