Net-Zero Buildings : Carbon Neutrality
Building related carbon emissions are among the highest across all industries. Operational and embodied carbon emissions account for a total of 39%. In this regard and to meet green buildings and the Sustainable Development Goals, the construction sector has become increasingly committed to carbon neutrality and has been working to develop building designs which result in negative energy buildings.
Numerous definitions are out there to define what a net zero or negative building is and they are not always aligned. All in all carbon negativity or net-zero carbon is “the reduction of an entity's carbon footprint to less than neutral, so that the entity in question has a net effect of removing carbon dioxide from the atmosphere rather than adding it.”
So in relation to buildings; a net-zero building is one that through the balance between the emissions and the absorption of carbon during the planning, the construction, the life and the demolition of it, have a net total (or negative balance) of removing carbon dioxide from the atmosphere rather than adding it.
What are the causes of carbon emissions in buildings?
Most carbon emissions come from the manufacturing of some building materials, such as concrete, steel, and masonry. Actually, when taking materials lifecycle into account, embodied carbon emissions in buildings account for 11% of the total greenhouse gas emissions emitted worldwide. A number of other factors contribute to these emissions, including chemical reactions, materials transport, end-of-life materials, and the incineration of plastic among others.
As such it is imperative that in the design process of buildings we consider how to facilitate future modifications and flexibility of space usage, reuse, dismantling and recycling of components and materials in a sustainable way. Additionally, by using low-carbon materials that will not produce carbon emissions during their manufacturing process and end of life, the various stakeholders in the construction industry can contribute to producing more sustainable buildings.
How can we reduce carbon emissions in buildings?
First, the design of the building is very important to reduce energy demand and consumption by selecting low carbon materials, considering design choices in their whole life cycle and relying as much as possible on non energy reliant technologies to heat, cool or light the building, such as passive design strategies that use natural air flow, fans, or heat pumps, over fossil fuel reliant technologies.
It’s also important to optimize the use of daylight which allows us to limit artificial light and thus energy consumption.
Net-zero carbon buildings must also integrate renewable energy production and storage of energy.
Lastly, but most important, to achieve zero net emissions, gas emitted during the building construction and life will have to be offset by carbon sequestration.
As a general note, it is important to consider both not just operational carbon but embodied carbon emissions as well when designing low carbon.
How to achieve carbon negativity or neutrality?
Decarbonization is the process of reducing carbon emissions. We talk then about carbon sinks to offset the emissions produced during the building phase. The term carbon sink refers to the concept of absorbing more carbon than it emits. In nature, the main carbon sinks are the soil, forests and oceans but these are now threatened by global warming. In fact, carbon stored in natural sinks, such as forests, is released into the atmosphere through forest fires, land use changes or logging. This is why it is essential to reduce carbon emissions to achieve climate neutrality as soon as these emissions are emitted.
These carbon sinks are mostly integrated to buildings by selecting materials which provoke photosynthesis such as algae walls and vegetation within or around the building. We can also speak about carbon sequestration when selecting biobased materials which are carbon negative through their own biology and composition where they had the ability to act as carbon sinks throughout their growth.
To learn more: Join Our Event "The Green Real Estate: Beyond Net Zero" on February 9th 2023!
