Buildings 20% of NZ’s carbon footprint, We need to do better – Jasmax

We need to do a lot better.

Sarah Leggett, a building scientist from Jasmax responds.

Currently almost everything we do is polluting, inefficient and wasteful of resources on some level. But, as a society, we’re seeing the shift across all fronts to net zero impact in everything from food wrap to fuel. As designers our responsibility is to drive change for greener buildings.

Disrupting the construction industry to reduce carbon impact is a big challenge. Production and transportation of building materials, architectural design, structural design, and construction method, would all be impacted. Do you go hard and advocate for transformative change, or do you tackle the challenges step by step?

In 2015, alongside Ngāi Tūhoe, Jasmax achieved New Zealand’s most advanced sustainable building– currently one of only 23 Certified Living Buildings in the world, and the only example outside of the US. It generates its own clean energy sources and collects its own water, processing all of its own waste naturally, and is wholly constructed from non-toxic materials. Going one step further, it was required to offset all the embodied energy and carbon required to build it. It proves that change is possible. However, what we have to understand is that this degree of transformation or positive impact isn’t currently possible for every project or in every situation. That said, what can be done?

Part of my role as a building scientist is to run simulations on buildings in the early design stages to predict their performance. Everything is quantified from energy efficiency, to lighting and thermal efficiency, and the comfort of the occupants. By modelling these simulations, we can estimate for example, how much a building will cost to run and provide return on investment of sustainable design for our clients. A recent project, the new three storey 6400m2 architecture and engineering school Kahukura at the Ara Institute in Christchurch, was designed based on feedback from this type of early performance modelling. It was predicted to run 65% more efficiently than if it was designed to Building Code. The building is ‘Net Zero Energy Ready’ and the net total annual energy savings compared to an existing block on the site equates to approximately $130,000 and a respective CO2 reduction.

Pegasus Primary School, also in the Canterbury region, used building modelling early in the design for a Net Zero Energy school. The modelling assisted in designing an efficient base building, optimising efficiency through high levels of insulation, double glazing, good solar management and well considered light capture.

The building is fitted with 560m2 of solar electric panels. The efficient construction systems complement the solar panels. In addition, energy monitoring is displayed on visual dash boards for the school to consciously manage their energy use. It’s estimated 60% of energy use within the building is attributed to occupant behaviour; use of plugs, efficiency of equipment and behaviours. The solar panels feed electricity and hot water into the school and any excess ‘stored’ goes to the national grid. They generate about $28,000 of power per year (at 18c/kwh) and reduce carbon emissions by nearly 30 tonnes per year.

To put that into perspective, one tonne of carbon emissions takes 15 trees over a 30-year period to sequester. The reduction in carbon emissions made by the green design of Pegasus School is equivalent to 450 trees planted in the ground for 30 years.

We have been using this type of analysis for the last 10 years. Jasmax’s goal is to achieve 75% greater efficiency than Building Code requires. With early performance modelling it is not too difficult to explore how we can streamline operational efficiency for our clients over the 30-50 year life span of their buildings.

Currently, I’m working on modelling strategies to reduce energy use in a number of large scale residential projects. There are some important conversations happening around affordable, comfortable and healthy homes with low energy consumption.

Passive design strategies, those that capitalise on natural ventilation, heat gain, daylight, shading, orientations and site response, are of minimal cost and yet their effect can significantly reduce electricity and energy costs within a building.

There are many factors key to designing as high a performing building as possible. Early performance modelling to inform design, careful selection of materials, and finally, ensuring that we communicate the potential of these buildings.