NZCEL has been looking into how we as a company can reduce our impact on the environment. According to the Ministry of Business, Innovation and Employment (MBIE) the Building and Construction Sector is responsible for 20% of New Zealand’s carbon emission. This includes operational energy (lights, heating, appliances etc.) and embodied carbon from the construction, maintenance, and demolition of buildings.

While we as structural engineers have very little to do with the operational energy usage of a building, our choices can have a large impact on the embodied carbon of a building. And as more efficient appliances are made, and greener sources of energy are harnessed the onus on the embodied carbon to be reduced will increase.

MBIE is in the process of creating a framework for reducing the carbon emission of the Building and Construction Sector. The planned implementation of this framework begins with requiring the calculation of the embodied carbon of all new buildings . This will lead into a cap on the allowable embodied carbon of a building, that will decrease overtime until net zero buildings is reached. While no timeframe for implementation has been decided on, we as a building community already have the tools currently to measure the embodied carbon, and the options to reduce our embodied carbon.

At NZCEL we have been using Institution of Structural Engineers’ “How to Calculate Embodied Carbon” to assess the embodied carbon of some of our projects, along with the affect some changes in designs we have made. In some of our recent projects we have used Cross Laminated Timber (CLT) panels as a part of our flooring system. We compared the embodied carbon of two similarly sized recent designs, one with a traditional concrete floor and one with CLT flooring system, to see the difference CLT makes. In comparing these two projects we found that using CLT as a part of the flooring system saved around 70 tons of CO2e for a floor area of roughly 1,250 m2. This is roughly equivalent to driving 350,000 km or driving from Bluff to Cape Reinga 170 times.

While CLT flooring systems are an excellent way of reducing a buildings carbon footprint and building weight (and therefore earthquake loads), there are still challenges in designing and using CLT. As it is a relatively new product there are few “accepted solutions” that will allow for fast design and consenting, and steel diaphragms are often used in tandem with CLT to simplify construction and design.

Manufactured timber products will become more common place in design as we look at how we can reduce our carbon footprint. An increased focus on our impact on the environment as an industry is leading to more research and alternative solutions to simplify design and construction.

At NZCEL we are increasing our competency in timber design so that we can provide high quality designs with lower impacts on our planet. As we are continuing to increase our understanding of how to calculate and reduce the embodied carbon of the structures we design, we will be able to provide a running start when the new framework is implemented.

For more information on MBIEs proposed framework for embodied carbon reduction follow the link below

https://www.mbie.govt.nz/dmsdocument/11794-whole-of-life-embodied-carbon-emissions-reduction-framework

For more information on how to calculate embodied carbon follow the link below

https://www.istructe.org/IStructE/media/Public/Resources/istructe-how-to-calculate-embodied-carbon.pdf

To calculate your own carbon footprint have a look at the toitū calculator

https://calculator.toitu.co.nz/