How to build more sustainably
Exploring ways to minimize construction and building waste is a passion for Dr. Terri-Ann Berry, Director of the newly formed Environmental Innovation Centre (EIC). Terri-Ann has partnered with experienced Master Builder Nigel Benton to develop practical environmental solutions for the construction industry. The team at the Environmental Innovation Centre (EIC) will write a monthly column in Building Today on practical advice for managing construction waste and other environmental issues builders might come across.
What is carbon and how does it impact our industry?
When building materials are created, ENERGY is required to make them. The energy may come from burning fuels like oil and coal, and in doing so, this creates carbon dioxide emissions. The problem with carbon dioxide is that when there is a lot of it in the atmosphere, it is very efficient at trapping heat from the sun close to the Earth. When the Earth’s surface gets hotter, things, such as our weather, get heated up worryingly. This can cause more floods, storms and generally more extreme temperatures on Earth.
Carbon dioxide is not the only culprit for heating the Earth's surface. Other gases like methane (which comes from livestock and landfills) also do the same thing. Together they are called Greenhouse Gases. When we talk about a building’s carbon footprint, we are referring to how much greenhouse gases are emitted while making a building. And of course, we would like to reduce our carbon footprint and carbon emissions as much as possible (which really means using as little energy as possible). The construction and operation of buildings account for about 20% of New Zealand's total carbon footprint (MBIE, 2020). New Zealand has committed to being zero carbon by 2050, which means we all must do our part.
Buildings use energy, which creates carbon emissions in two ways (Figure 1):
"Embodied carbon" - this considers carbon emissions coming from all the materials and energy required to create, maintain and dispose of a building. This covers the building's entire life cycle, from harvesting, importing, manufacturing and transporting materials, installing building components, maintaining and renovating the building, and finally, what happens at the end of its life. This is calculated using a life-cycle assessment (LCA).
"Operational carbon" - this carbon comes from using, working and living in a building (e g heating). It usually considers water and energy use.
In the past, a lot more attention has been paid to saving energy in a building to reduce operational carbon (which also saves the occupants money!). For older buildings, which tend to be inefficient, poorly insulated and poorly ventilated, operational carbon still plays a large part. For example, replacing electric heaters with a heat pump can reduce electricity use by up to 75 %. Operational carbon emissions can also be reduced by changing power supply, and changing how we work and live in a building.
However, over time, new buildings have become far more energy-efficient, resulting in less operational carbon emissions. As such, embodied energy now plays a larger part in a new building's carbon emissions. This difference in embodied and operational carbon emissions is more obvious in countries such as New Zealand, where our energy supply is predominantly renewable (hydroelectricity, geothermal, wind and solar) and low carbon. It is becoming more and more important to target and reduce embodied carbon emissions.
Unlike operational carbon emissions, embodied carbon cannot be reduced or optimised as it is mostly released upfront or during renovations. This means it is crucial to consider building materials and their life cycle before the construction of a building, at the design stage. You can reduce the embodied energy of the products or materials you use by:
Selecting products made from materials grown in NZ (e g wool or straw insulation)
Selecting products manufactured in NZ that don't have to be transported a long way
Choosing reused/repurposed or recycled products to save energy instead of throwing them away (Figure 2, a more circular approach)
Recycling your own construction waste so it can go to another use instead of being buried in a landfill
So now you have some simple steps that you can take to start reducing both operational AND embodied carbon emissions by designing energy efficient homes and choosing locally made products.
In next month's issue, we will be discussing one way that the Operational Carbon can be reduced - by improving the ventilation in a house through mechanical ventilation and/or natural ventilation.
If you have any questions for the team that you would like answered in this column, please contact us.
Resources:
Ministry of Business, Innovation and Employment (MBIE). (August 2020). Whole-of-Life Embodied Carbon Emissions Reduction Framework: Building for climate change programme.
Alwan, Z., & Jones, P. (2014). The importance of embodied energy in carbon footprint assessment. Structural Survey, 32(1), 49–60. https://doi.org/10.1108/SS-01-2013-0012
Strain, L. (2017, May). Time Value of Carbon. Carbon Leadership Forum. https://carbonleadershipforum.org/the-time-value-of-carbon/