01.10.2020 : Scott Smith

Accelerating building decarbonisation

Just over a week ago, Cabinet issued a press release on their procurement priorities to “promote jobs, Māori and Pasifika businesses and sustainability”. One sentence has wide ranging implications for the design of buildings in New Zealand. 

“Cabinet has also agreed that when constructing new buildings, mandated departments and agencies will be required to assess the greenhouse gas emissions resulting from the materials and construction processes used. Agencies should choose those which have the lowest upfront carbon emissions” 

This directive provides a game-changing opportunity for our industry to focus on low carbon building materials and construction practices. On the other hand, there is a risk it could drive investment away from more impactful de-carbonisation opportunities such as energy efficiency, and co-benefits such as occupant health and wellbeing.  

We provide our thoughts on how this directive can proactively support industry to transition to new ways of designing, building and operating vertical infrastructure for a low carbon future. 

Firstly, some background. 

The built environment, by some accounts, contributes up to 20% of NZ’s Greenhouse Gas emissions. At a macro level, about half of these emissions are “embodied emissions” – i.e. the emissions associated with the extraction and production of building materials, transport to site, and construction activities. The other half is “operational emissions’ – i.e. emissions associated with in use activities such as heating, ventilation, lighting, computers and other building systems. A small proportion of emissions are also associated with end-of-life, demolition activities. 

This directive specifically talks about the embodied or “upfront” carbon emissions. 

The requirement to assess embodied emissions will capture a significant emissions source that is often not considered in New Zealand. Until recently, the industry’s focus has been on operational emissions. This is because the most cost-effective carbon reduction opportunities relate to operational efficiency improvements and the displacement of fossil fuels (e.g. removing reliance on coal or gas heating). 

The Government’s directive to deliver the “lowest upfront carbon emissions” will require the building industry to shift its focus towards embodied carbon. 

There are good reasons to prioritise embodied emissions. Not only does it address a missing piece of the carbon puzzle, it also positively disrupts high carbon supply chains, creates new employment opportunities in New Zealand for Māori and Pasifika, supports the interests of Iwi investment in forestry, and positively reframes the building design process around carbon reduction. 

But there is a risk. 

The proportion of emissions associated with upfront, operating and end-of-life stages are different depending on the type of building being considered. For example, a highly serviced building, such as a hospital, generates a much higher proportion of carbon emissions associated with operations. 

If you targeted the lowest upfront carbon emissions, then you may direct capital away from the greater opportunities associated with operational emissions. Further, the lowest capital carbon option is not always the lowest overall carbon option. For example, the use of double glazing increases the carbon footprint of the building envelope, but decreases the building’s operational carbon footprint.  

The intent of this directive, to accelerate the industry’s focus on embodied carbon emissions, is much needed, but it should be broadened to ensure the most significant emissions associated with each building type are addressed. 

The best way to do this is to target the lowest “whole-of-life carbon” emissions. This is analogous to a financial whole-of-life cost analysis as it reconciles both embodied and operational carbon emissions. This enables the best allocation of investment and maximises the carbon reductions achieved.  

How the design of buildings is approached must also change. Early decisions on building form are not usually informed by carbon analysis. Opportunities, such as the use of a timber structure, are often lost due to the default application of traditional design solutions. The ideal design process integrates specialist experience before a designer’s pen hits the paper. This will help capture carbon reduction opportunities early on. 

You also need clear targets. We have the knowledge and ability to design low carbon buildings, but there is very little consensus on what is “good enough” in the built environment. We know that by 2050, whole-of-life carbon for a new development must be zero. But what about a building being constructed today, or one built in 10 years’ time? Targeting the lowest upfront carbon is a good philosophy, but there really needs to be a science-based carbon budget for each building design, aligned with New Zealand’s future emissions trajectory. 

Many organisations want to play their part, but often don’t know how they contribute to the bigger picture. The ideal situation is to be able to cascade New Zealand’s national carbon targets down to carbon budgets for individual projects. To help meet this challenge, Beca is developing an interim methodology that can be used to set carbon targets for our buildings projects and drive designers to innovate. 

With Government’s commitment, a whole-of-life carbon perspective, an integrated design process, and clear emissions targets, we can deliver the change that New Zealand needs. 

You may also be interested in Episode 6 of our 'Getting to Carbon Positive' series, which covers the opportunities the COVID-19 recovery presents to decarbonise the Built Environment.

About the Author

Scott Smith

Senior Associate – Building Services

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