Designing the net-zero carbon homes of the future

Decisions made today about the look and feel of new houses will affect the many people who live in them in the decades to come.

drawing of housing units with solar panels
Master of Building Science graduate Brian Berg, now Kāinga Ora’s Manager of Carbon Neutral Housing, is more aware of that than many.

Brian is a New Zealand leader in designing low-carbon homes and buildings with sustainability strongly in mind.

He was recently the driving force behind Ngā Kāinga Anamata (homes of the future), which featured in the United Nations Climate Conference COP26 in its “Build Better Now” virtual pavilion.

The ground-breaking project aims to cut carbon emissions in New Zealand’s building industry, and was selected from more than 900 global entries to be one of 17 initiatives on show at COP26.

Brian came to Te Herenga Waka in 2009 to study building science, having already completed studies and worked as an architectural draughtsmen. This is where he realised that successful buildings are far more than how they look.

During his Bachelor and Master of Building Science degrees, he learnt buildings could and should be so much more, by focusing on the comfort of people living in them and their impact on the planet.

At the time, Brian’s supervisor Associate Professor Michael Donn of the postgraduate building science programme was researching net-zero energy buildings as part of the International Energy Agency’s work.

This was an international collaboration of universities and research agencies on how to design buildings that were comfortable for people, used very little energy, and what energy they did use was generated by onsite renewable energy sources, such as photovoltaic solar panels.

“I wanted to be part of this work, but I also thought to myself, all this research is focusing on the energy and carbon impact of buildings during their operation, but what about the energy and carbon emissions from their materials?

“The manufacturing of concrete, steel and other building materials are all significant contributors to global warming and resource use. As all our buildings progress to net-zero energy status, the carbon emissions associated with building materials, called lifecycle-embodied carbon, will be an emerging challenge.

Brian’s Master’s and subsequent research career saw him develop a methodology and tool for architects, engineers and other building designers to calculate the carbon impact of buildings and their design decisions. “The aim of this tool is to help experts reduce the carbon impact of building below a 1.5°C carbon budget of about 10.6 tonnes per occupant, which is about an 80 percent reduction compared to most new homes.”

Brian considers homes as social infrastructure for all Kiwis, “just like our roads, electricity network, and three waters”.

“The homes we build now we will pass down for future generations—both the good and the bad ones. The decisions we make during the six months of building design will leave a legacy for decades.

“Think how many different families live and play in a home over its 70- to 90-year lifespan? That is why we need to design and build healthy, comfortable, sustainable, affordable homes today. We need to maximise the largest residential construction building boom for generations, and set future generations up for success.”

As our lifestyles become more sustainable, homes and buildings can play a significant role in decarbonising New Zealand, Brian says. “I think of buildings as resource hubs for our net-zero carbon world.”

In his role managing the carbon-neutral housing programme at Kāinga Ora, Brian aims to speed up the development and adoption of sustainable and decarbonising designs and technologies within the agencies’ state/social housing construction programme.

This involves pilot and innovation projects such as the Bader Ventura and Harvard Passive House apartment buildings in Māngere, as well as Ngā Kāinga Anamata.

Ngā Kāinga Anamata will see Kāinga Ora build 30 state/social homes within five, three-level apartment buildings in Auckland. Each building is near-identical but uses a different construction technology, enabling comparisons on sustainability benefits across a range of building materials,structural systems, and offsite manufacturing.

“This project marks the start of a national response to climate-change mitigation in the built environment,” says Brian. “About 74 percent of the lifecycle carbon was designed out by using solutions we already have, such as the Certified Passive House (Passivhaus) Standard, net zero energy technology, and low-carbon materials like cross-laminated timber.

The project is the culmination of research into building and design carbon impact which Brian began at the University on his Master’s course and continued while a building environmental scientist at the Building Research Association of New Zealand. “Nga Kāinga Anamata’s carbon impact is approximately 14.5 tonnes or 1.4 times the carbon budget, so it is a case of job started, albeit a very good start, but not job done.

“It’s both a professional and personal highlight to be leading the carbon and building physics/performance aspects of Ngā Kāinga Anamata, and it’s wonderful seeing the work I first envisioned at the University manifesting itself in a world-leading project that will help transform the building sector towards its net-zero carbon future.”