Pathway to net-zero carbon design

This Issue This is a part of the Net-zero carbon buildings feature

By - , Build 182

Jasmax, one of New Zealand’s oldest architecture practices, is moving to tackle climate issues with the launch of a staged roadmap to designing net-zero carbon buildings by 2030.


JASMAX RECENTLY launched its Pathway to Net Zero Carbon Design. The project sets specific performance targets for non-domestic buildings for 2020, 2025 and 2030, with the aim of achieving carbon-neutral buildings by 2030.

UK guide an inspiration

The work draws heavily on the Sustainable Outcomes Guide published by the Royal Institute of British Architects (RIBA) in 2019 but translates it to apply better to New Zealand’s built environment and building industry. New Zealand buildings have seismic resilience requirements that don’t apply in the United Kingdom, and our materials delivery chains are different.

The RIBA document measures sustainable outcomes in eight areas, including embodied carbon in materials, carbon dioxide emissions in building operation, sustainable life cycle cost and human health, wellbeing and social values. There are separate targets for domestic and non-domestic buildings.

Performance targets for three areas

Jasmax is starting with performance targets for three areas – operational energy and carbon, whole-of-life embodied carbon and potable water use (see Table 1). Jasmax Principal Architect Chris Scott says other targets will be introduced in due course. ‘We are not losing sight of the others, but they are harder to set targets for and we didn’t want to wait.’

Embodied carbon is the amount of greenhouse gases, expressed as carbon dioxide equivalents, required to produce materials and maintain and demolish a building.Sometimes carbon is just measured to the point materials are delivered to site, but this doesn’t give the whole story.

The Jasmax measure is cradle to grave – the whole-of-life cycle. This includes the demolition/disassembly of a building at the end of its useful life. A lot of the carbon in this measure can be found at the end of a building’s life.

Table 1 Targets set for three metrics in non-domestic buildings

Assessing existing projects

The practice has already assessed a range of recent and current projects to see how they measure up. The results are encouraging. The 2017 Mana Hauora building at Auckland University of Technology (AUT), after some operational fine-tuning, meets the 2025 operational energy target of 65 kWh/m2/year.

One completed building using 4-storey timber framing, the University of Canterbury Beatrice Tinsley Building, included adaptive reuse of existing 1960s concrete foundations from an earlier building. ‘Calculations for the new structure showed that it is close to the targets we had set for 2025 (it was 630 kg CO2e/m2), so we know it can be done,’ Chris Scott says.

The measures involve looking at the serviceable life of all the different elements of a building. For example, one building with a photovoltaic system installed just missed complying with the 2030 target for embodied carbon because the photovoltaic system on the roof will need to be replaced before then.

Initially, targets will be applied to commercial and educational buildings where the metrics are easiest to measure. Some other types of building – such as hospitals or scientific facilities – have special requirements that make assessment more complex.

Small cost for big commercial benefit

‘We aim to eventually measure all our buildings. Cost is not really a barrier. As a proportion of the total cost of a project, doing these calculations is ridiculously small,’ Chris Scott says.

‘Some clients have a huge appetite to get this right – universities and some government agencies, for example, but also quite a few commercial clients. There can be a commercial benefit.

‘Developers can take the approach that, if the market is volatile or at risk of dropping, they can choose to have the better product. If they opt for the poorest-performing products in the market, they could end up stuck with them in a downturn. Anyone who just focuses on meeting minimum standards could be in trouble.

‘But this whole thing is not purely about numbers – we are working to develop an intuitive understanding of how to build lower-carbon buildings. We don’t want to end up with an over-reliance on calculations – we want to get a feel for what makes a difference.

‘We have already learned a lot quite quickly. It is a matter of getting the thinking right at the start. In many cases, carbon reduction is about leaving materials out as much as choosing the right materials.’

Good passive design is key

Jasmax architect Paul Jurasovich points out that a key element to better performance is getting the passive design right – something their larger projects share with small-scale domestic architecture.

Tackling overheating

‘Getting the envelope right, getting the glazing in the right place is crucial. A lot is about keeping the heat out or dissipating heat, especially in buildings with high human occupancy, large numbers of computers and so on, which create high heat loads. With education and commercial buildings, overheating can be a problem in winter too.’

The Mana Hauora building tackles the overheating risk in two ways. First, external fins on the high-performance façade exclude unwanted sun. Inside, a system of freshair displacement ventilation – distributed through raised access floors – provides passive cooling for much of the year. The system may pay for itself within 5 years thanks to savings in purchased energy plus savings in maintenance.

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Fine tuning once occupied

After occupation, tuning to eliminate unnecessary artificial lighting and better manage indoor temperatures can further reduce operational energy costs. At the Mana Hauora building, for example, tuning allowed AUT to reduce energy consumption from 77 kWh/m2 within 2 years of opening.

Good for large and small practices

Chris Scott and Paul Jurasovich say that the Jasmax initiative isn’t just an option for larger practices with their personnel numbers and resources. They are keen to see basic tools developed that allow smaller practices to do the same thing. The process needs to be flexible and appropriate for the scale and impact of the individual project.

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