Home Style Green - Sustainable Design and Building

The New Zealand Building Code does not guarantee performance in all areas that many homeowners might expect. Fortunately, Homestar is available to close the performance gaps.

Homestar Headline Benefits
•    Fresh air
•    Dry
•    Comfort
•    Carbon  

Homestar Design Checklist
This is a summary of the basic requirements over and above basic building code compliance for achieving 6 Homestar v5. Inclusion of everything here does not guarantee compliance but is a starting point for what should be considered.

  • Homestar Designer: This can be someone within the project team or an external consultant. Engage them in the process as early as possible.
  • Energy model: Homestar v5 uses predicted performance criteria rather than a schedule of allowable insulation levels. The performance criteria include estimated energy consumption, winter and summer internal temperature and likely carbon emissions and these can be calculated using the Energy and Carbon Calculator for Homes (ECCHO). Energy modelling used to be a highly specialised process and expensive process. ECCHO makes energy modelling accessible to Homestar Designers
  • Continuous mechanical ventilation: Internal moisture is a significant problem for New Zealand homes and there is adequate evidence that the building code requirements of openable windows is not reliable for providing enough fresh air and removing dampness. There are simple solutions available for 6 Homestar that are nearly silent, cost very little to run and will provide much more reliable benefits to homeowners.
  • Thermally broken windows: Pay attention to the window frames, not just the glass.
    Slab edge insulation OR above slab insulation: Junctions such as the connection between walls and floors are risk areas for condensation. Some additional insulation detail can help prevent this and can be easily incorporated when considered early.
  • Water efficient fittings: These are commonly available. Select the best WELS rated products. 

For more, visit https://nzgbc.org.nz/introduction-to-homestar

Direct download: Build_Aotearoa_13.MP3.mp3
Category:general -- posted at: 8:16pm NZST

Scott Fisher is the CEO of Offsite NZ. I caught up with him to discuss the history, current practice and future opportunities of offsite manufacturing in the building industry in Aotearoa. 


Direct download: Build_Aotearoa_12_Offsite_NZ_with_Scott_Fisher.mp3.mp3
Category:general -- posted at: 12:15pm NZST

While researching a presentation to open the NZGBC 2024 Housing Summit, I looked into the climate initiatives of Europe and the US. 

In Europe, over 83b has been recently been committed by the European Parliament as part of the Energy Performance of Buildings Directive. The ultimate goal is that the building sector will be climate neutral by 2050. Importantly, there are interim goals for 2030 and 2040, which encompass both new buildings and retrofitting existing buildings. 


Over in the US, there is the Inflation Reduction Act which will see a staggering $783b invested into energy security and climate change initiatives. 


Back here in Aotearoa, aside from recently updating H1 Energy Efficiency in our building code, MBIE has laid out a programme called Building for Climate Change. 


The implementation plan for BfCC has reporting requirements suggested for 2025. 

Direct download: Build_Aotearoa_11_Global_Climate_Progress.MP3.mp3
Category:general -- posted at: 3:53pm NZST

This week I attended a BRANZ seminar titled 'Building for our changing climate'. Tāmaki Makaurau Auckland was the last stop on the BRANZ seminar tour of the country and it's encouraging to think that rooms of designers, builders, product suppliers, building officials and others, were interested enough in this topic to take four hours out of their week. 

A key takeaway is that we're not prepared. We're already handicapped by having insufficient standards in our building code to deal with our current climate. With the forecast being 'warmer and wetter', the situation is set to get worse.


Direct download: Build_Aotearoa_10__Warmer_and_Wetter.MP3.mp3
Category:general -- posted at: 9:10pm NZST

Steve Penny is the founder and director at Honoris, a building services consultancy in Christchurch, New Zealand. He is also the host of his own podcast, A Penny for Your Thoughts.

Direct download: Build_Aotearoa__9_with_Steve_Penny.MP3.mp3
Category:general -- posted at: 10:27am NZST

Many people might be surprised to know that the New Zealand Building Code does not require any consideration of overheating in homes. The energy efficiency requirements in our code are based only on the ability of buildings to keep warm without excessive heat loss. There is nothing to prevent homes from being designed with large areas of unshaded north or west-facing glass.

Siân Taylor is an Architect and Passive House Designer based in Queenstown. She has experience creating homes that are designed to perform well all year round, in some of the most challenging and spectacular locations.

Follow Siân on Instagram and check out Team Green Architect's latest work at https://www.teamgreenarchitects.co.nz/.

Direct download: Build_Aotearoa__8.MP3.mp3
Category:general -- posted at: 4:15pm NZST

Stärke has been in the window industry in New Zealand since the 80s. They were at the forefront of supplying aluminium frames to the building industry but have recently made some big changes. With a focus on building performance, Benjy Simmons describes the new direction of Stärke as a 'once-in-fifty-year' change. While the company has a long legacy, they've experienced rapid change over the last few years. 

Benjy credits some of the openness to change to him being from outside the industry. He's come in with a different perspective. "We're beginning to see ourselves as a building performance company not just a window and door company", says Benjy. 

Check out the full range of Stärke products along with their education pages and other resources.

Direct download: Build_Aotearoa__7_Starke_Windows_and_Doors.MP3.mp3
Category:general -- posted at: 3:36pm NZST

More is not always better, especially regarding the amount of timber in the frame of a house. The more timber there is, the less space there is for insulation. The way this is measured is called timber fraction.

Most homes in Aotearoa are designed using the assumption that timber will make up around 14% - 18% of the area in a wall. A 2020 BRANZ research study found that in reality, the average timber fraction is closer to 40%. This means there is considerably less space available for insulation.

Unfortunately, this is not always picked up during the consenting or pre-lining inspection process. H1 Energy Efficiency calculations are checked at the design stage, usually using the much lower default timber fraction assumption. The result of all this is that many consumers are effectively getting less insulation than they're paying for, and much more thermal bridging. 

PlaceMakers has recently launched a new service providing a detailed report of the actual timber content for any wall frame and roof truss they supply. This accurate figure can then be used to provide true H1 calculations. Alternatively, a designer might choose to adapt their plan to reduce the thermal bridging and increase the amount of insulation.

National Technical Resource Manager, Pete Hammond explains how Framology works. We also discuss the option of using external insulating products like RigidRAP-XT from IBS to eliminate thermal bridges.

Direct download: Build_Aotearoa_6__Framology_with_Pete_Hammond.MP3.mp3
Category:Building -- posted at: 11:06am NZST

Denise Martin has been involved with many of Aotearoa's Passive House projects. As one of the most experienced blower door testers in the country, she's been involved with verifying a range of residential and commercial buildings both in New Zealand and Australia.

I caught up with Denise to chat about how she got into building science in the first place and some of the challenges and opportunities facing the building sector in New Zealand. We also discuss the building code, energy modelling, thermal performance and air tightness.

If you don't already, I highly recommend following Denise on Instagram, TikTok and LinkedIn.

Direct download: Build_Aotearoa_5__BEO.MP3.mp3
Category:general -- posted at: 5:30pm NZST

I found it confronting listening to Tova O'Brien's guest this past week as she described the experiences of staying in motel emergency accommodation with a young daughter. From my relative privilege (of choosing the right parents and having things turn out ok for me so far), I find it hard to imagine being in this situation. But it's the reality for nearly 6,500 people across Aotearoa, half of whom are children. 

This is an emergency, and the problem is complex. The solution will require more than simply building more houses because the underlying issues are more complex than that.

Related to this is a proposal from the Ministry of Business Innovation and Employment (MBIE) to review the building consent process in New Zealand. This is something I'd like to look at in more detail because we must get the balance right.

In 2023, MBIE sought public submissions in response to an options paper on a review of the building consent system. This week MBIE published a summary of the 270 submissions received.

At the other end of the spectrum, I caught up with Jonathan Holmes about living in a Certified Passive House Premium home and working on assessing the embodied carbon in our buildings. 

Other links for this week's podcast episode:

Be sure to register for Reimagine Buildings '24

Direct download: Build_Aotearoa_4_Quality_and_Quantity.MP3.mp3
Category:general -- posted at: 1:01pm NZST

Last week, February 22nd rolled around. This was a significant date in the Cutler-Welsh household thirteen years ago when our house was located close to the Avon River in Christchurch. While it was a life-changing day for us, life has gone on. We ultimately lost our recently renovated home in Richmond as a result of the Canterbury Earthquakes, but many lost so much more. 

What would a moratorium on consenting new buildings in known floodplains, tsunami or fire risk areas, look like? How would the resulting plummet in land values impact the economy and further inflate the cost of housing?

But if not now, when? The risks are likely to get higher and ultimately we have to ask ourselves if we're prepared to keep making our stop-banks higher or retreat to higher, less shaky ground.

Direct download: Build_Aotearoa_on_Safeish_Ground.MP3.mp3
Category:general -- posted at: 8:43pm NZST

There are fundamental gaps in what the New Zealand Building Code covers and how well it covers the aspects that are included. These reasons should be enough to justify using standards like Passive House or Homestar to go above and beyond the building code.

In this series, I'll be looking at reasons why it's better to ask about the value and risk minisation resulting from higher performance standards rather than focussing only on perceived upfront cost. 

Direct download: Build_Aotearoa_2_Principles_and_Performance.MP3.mp3
Category:general -- posted at: 12:56pm NZST

As I draft this episode, there's a chorus of cicadas outside my window. The sun is shining and there's a faint breath of a breeze. It seems calm where I live, here in a relatively leafy part of Tāmaki Makaurau. 

But all is not calm everywhere in Aotearoa today, Waitangi Day 2024.

Direct download: Build_Aotearoa.mp3
Category:general -- posted at: 5:21pm NZST