When a company insists that they deliver ‘low carbon construction’ it’s a good idea to ask a few questions.
The first might be, ‘What do you actually mean’? Low carbon construction is a wonderfully vague term. Lower compared to what? Is it just operationally lower in carbon or is embodied carbon lower too?
What you really want to see are hard numbers. How much embodied carbon will there be associated with the building? What are the specified u-values and air permeability figures, and how will these be guaranteed in practice?
Numbers don’t Lie – Neither do Materials
You’ll find further important clues (particularly related to embodied carbon) by looking at the specified materials.
There are materials that claim to have a lower impact on the environment. Fossil-free steel and low carbon concrete, for example. These are significant developments. Where the use of steel or concrete is unavoidable, lower carbon alternatives will help.
But they still have a carbon footprint. Even a material that generates zero net carbon emissions in production will have embodied carbon associated with transport and onsite assembly.
Given the current transport and power generation infrastructure, for every construction project there are multiple entries into the plus column of the carbon account.
What’s needed is something to go into the ‘minus’ column. Ideally this won’t be offsetting. By definition offsetting doesn’t reduce carbon emissions.
Timber has a negative value for embodied carbon. Trees absorb carbon from the atmosphere and store it as biogenic or sequestered carbon. The carbon is locked away until the wood decomposes or is burned.
So, structural timber incorporated into a new building will reduce the overall level of embodied carbon. You could argue whether the term ‘low carbon’ should be used for any construction project that doesn’t have a high structural timber content.
In the absence of agreed definitions or standards the best options are to use a tool such as the Innovaré Carbon Calculator, or simply to look at the material specifications to discover the overall timber content. These will tell you more than the term ‘low carbon’.
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