Landmark Study Shows How to Change the Building Sector From a Major Carbon Emitter to a Major Carbon Sink

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Updated December 10, 2019

When made from the right materials, buildings can be a solution, not a problem.

We recently called Chris Magwood a TreeHugger hero for his work on the embodied carbon of building materials. He has been a voice in the wilderness about the subject for a while, and just completed his university thesis on the subject. Now he has put his thesis into an accessible graphic form, which is available through a new organization, Builders for Climate Action.

Chris Magwood at the Green Building Show/ Lloyd Alter/CC BY 2.0

The study complains that "the response to building-related emissions has been to focus solely on energy efficiency, but this may result in initiatives and policies that will raise emissions rather than lower them." We have covered Magwood's work on this before, but it has never been more clear: Building a highly energy-efficient structure can actually produce more greenhouse gases than a basic code-compliant one if carbon-intensive materials are used.

When in fact, if designed out of the right materials, "we can feasibly and affordably capture and store vast amounts of carbon in buildings, transforming the sector from a major emitter to a major carbon sink."

The first, very important lesson is that we have to stop equating energy with carbon. So where now we have people talking about net-zero energy buildings or net-zero carbon, they are very different things. You can build a net-zero energy building that still puts out a lot of carbon, either upfront or through operating energy if it uses natural gas for heating.

© Builders for Climate Action

So we used to talk about embodied energy, but now we call it embodied carbon. And like me, Chris doesn't like that term; I use Upfront Carbon emissions (UCE), while he uses up-front embodied emissions (UEC). And where people never paid much attention to this, it's now a very big deal. If we are going to keep the temperature rise below 1.5°C, we have to stop building out of materials with high UEC right now. I am not crazy about this graph he used where the upfront emissions in gold are shown as not increasing (they do, because we build more buildings each year), but the point made is still true – between now and 2030, the vast majority of CO2 emissions from new buildings is from upfront carbon, not operating emissions.

© Builders for Climate Action

That means we should be building out of low-carbon materials at higher densities. Magwood's sweet spot is a four-storey multi-family building, which could be built out of materials that store carbon rather than emit it – straw, wood, linoleum, cedar.

© Builders for Climate Action

If you look at the volume of residential construction from 2017 and compare your standard residential construction to carbon storing building, there is an incredible difference.

There are many findings in this report that are counter-intuitive and that will be controversial.

Reducing upfront carbon emissions is more important than increasing building efficiency. "Up-front embodied emissions for buildings materials must be measured and policies enforcing caps developed for fast reductions."
Switching to clean or renewable energy is more important than increasing building efficiency. "Clean energy is critical for the building sector to meaningfully reduce its carbon footprint and policy efforts must be focused on this goal."
Net-zero energy codes will not significantly reduce emissions in time. "Policy makers and regulators must aim for true net zero carbon buildings, not net zero energy buildings."

Others are incredibly positive and give hope that we can actually use buildings for carbon capture and storage.

Available, affordable material options can reduce net up-front carbon to zero, eliminating this large source of emissions. "Building sector leaders should be ambitiously moving to make buildings with zero up-front emissions."
Material selection is the most impactful intervention at the individual building level, with reductions of up-front emissions of 150 percent. "Designers and builders can completely transform the carbon footprint of their buildings through carbon-smart material choices."

We also need to stop thinking about energy efficiency on its own; Magwood proposes the term Carbon Use Intensity (CUI): a mix of Upfront Carbon Emissions plus (energy use intensity x energy source emissions) = CUI

The results of this study demonstrate that we are capable of making low-rise residential buildings with a net zero embodied carbon footprint, and that we can even surpass this threshold and create buildings that actually have net carbon storage rather than net emissions. Plant-based materials STORE more atmospheric carbon than was emitted in harvesting and manufacturing. This opens a whole new category of building materials with CARBON REMOVAL AND STORAGE POTENTIAL!

Combining upfront and operating emissions

Magwood and his report make it very clear: buildings don't have to be part of the problem. They don't even have to be net-zero. They can actually become part of the solution to the climate emergency. They can be seriously carbon negative. There is no reason that we couldn't build much of our low-rise housing this way; many others have also noted that the "missing middle" housing is the most economical option for building affordable housing quickly.

Chris Magwood and the Builders for Climate Action have demonstrated a path that can make low-rise, missing middle buildings into a climate change solution. They have laid out the steps that we need to follow. It's doable, and we have to start right now. Read the entire report and support Builders for Climate Action.