COP26 is dedicating Nov 11 to the built environment, and has selected housing agency Kāinga Ora to exhibit its green-starred new development there – but NZ’s building industry has a long way to go, says carbon neutral housing manager Brian Berg
Opinion: The New Zealand Government has recently announced the goal to halve net greenhouse emissions by 2030. For the building and construction sector, a sector both responsible for a fifth of these emissions and currently in the middle of the largest construction boom in decades, there is both good and bad news.
The good news is this target is possible today – technologies, materials and systems already in the market today can deliver significantly better/lower carbon homes. A low carbon building does not need to rely on behaviour change to be successful and it does not have to disrupt how Kiwi want to live.
The bad news is it will take some effort to change the way the industry currently does things to deliver this future and that the time to do it is now.
Under current build standards, new residential builds emit more than five times the carbon a 1.5°C target allows – requiring an 80 percent reduction in carbon emissions to be climate safe.
Homes built today are not only releasing carbon during construction but are locking in emissions for the lifecycle of the building and the decades to come. Urgent action is needed by our building sector now, if it is going to do its part in decarbonising New Zealand by 2030 and beyond.
The carbon trifecta
A reduction in carbon emissions for the entire lifecycle of a building, needs a focus on three key areas: embodied carbon, operational carbon, and local renewable energy generation.
Embodied carbon refers to all the materials used over the full lifespan of a building. This includes manufacturing materials, transport and construction, the building’s maintenance and replacement of materials, as well as the end of life demolition/deconstruction. Solutions to reduce embodied carbon need to consider the impact over the entire building lifespan (anywhere from 50 to 90 years).
However, embodied carbon only accounts for the emissions of the physical house, not those required to ‘run’ or ‘operate’ the home. Operational carbon is the emissions associated with energy and water used by the home’s occupants, such as the electricity for heating and cooling, ventilation (such as extractor fans), hot water, and providing electricity to the wide range of appliances used on a day-to-day basis.
In a typical New Zealand home, operational carbon represents around 80 percent of the total carbon impact, whereas embodied carbon only 20 percent. However, this spilt does not account for when these emissions are released, or the impact that carbon-based decisions made today will have on the future.
Operational carbon emissions are spread out over a building’s 50 to 90-year lifespan, however they are essentially ‘locked in’ at the design stage, when building decisions such as structure, size and insulation, are made. Conversely, the majority of embodied carbon emissions, while small in comparison, are almost all released during the manufacturing and construction stages of a building’s lifecycle.
This means that for the current construction boom, the decisions being made right now will determine how ‘low carbon’ our homes, communities and cities are for the decades to come.
Local energy generation completes the carbon trifecta, with solar panels being the obvious choice in 2021 for homes. In the short term, solar panels can generate electricity at a carbon intensity lower than our national electricity grid’s annual average, and for public housing they can provide free electricity to people who need it most.
In the long term, solar panels can help reduce future electricity demand issues as other sectors turn to electricity to decarbonise (e.g. electrification of vehicles, manufacturing and industrial processes).
Nothing is emissions free when it comes to carbon, and while solar panels will reduce operational energy, they will have an embodied carbon impact that, along with demand/supply load matching, must be optimised on a whole of lifecycle perspective along with a two-way interaction with the national electricity grid and network.
Homes of the future
Kāinga Ora has a strong focus on this carbon trifecta in its new sustainability pilot, Ngā Kāinga Anamata (meaning ‘homes of the future’) in Auckland’s Glendowie, with very promising results so far.
Ngā Kāinga Anamata looks at embodied carbon in five different, but commonly used, structural materials used in each of its five near-identical buildings. High durability or low-embodied carbon has also been prioritised in the selection of other materials.
When it comes to operational carbon in the project, leading sustainability standards such as the New Zealand Green Building Council’s Homestar rating (like the Green Star rating but for homes) and Passive House, are employed.
Homestar is a national rating tool to evaluate homes in terms of their warmth, as well as their health, sustainability, energy and water efficiency qualities. In 2019, Kāinga Ora committed all its new builds to be built to 6 Homestar standard, meaning homes will exceed Building Code standards for warmth, dryness and health. Ngā Kāinga Anamata is on track to achieve 9 Homestar.
The Passive House Standard originated in Germany. It is recognised internationally as a best practice benchmark for low energy use, indoor environmental quality and health performance, especially when applied to social housing.
Features such as airtight construction, high insulation levels, high-performance windows and mechanical ventilation with heat recovery systems, mean active heating and cooling can be almost completely designed out of buildings. The energy required to heat water is reduced through the use of heat pump technology to only use one third of the electricity required by a conventional electric hot water system.
Finally, all five of these buildings will be installed with rooftop photovoltaic array, or solar panels, to power all homes in the development.
The late design-stage reports indicate these solutions will provide as much as a 74 percent reduction in lifecycle carbon compared to typical construction. It proves that very low carbon, healthy, net zero energy homes are possible with today’s technology, and are critical for Aotearoa to transition to a 50 percent emissions reduction within the next 9 years, and a net zero carbon economy by 2050.
Making changes today
The design of Ngā Kāinga Anamata has already proven the technology to achieve the Government’s targets is available in the industry today.
Construction of the project will now demonstrate New Zealand can build low carbon homes, and do so at scale. However, with all construction today affecting our carbon emissions for decades to come, it will take an all-of industry effort to build and protect our future.
New Zealand’s recent international commitment is to cut carbon emissions by 50 percent by 2030 to stop global warming exceeding 1.5 degrees Celsius.
However, the time for the building sector to act is now. Designs created today can reduce embodied carbon and slash operational carbon for the many years to come. The sector needs to ‘go fast and go hard’ in the adoption of low carbon solutions to play its part in New Zealand’s emissions reduction effort.
