Groundbreaking Study Highlights How Design and Development Decisions Affect Embodied Carbon

The lessons of a study from Halifax, Canada can be applied anywhere.

Halifax Harbour
Halifax Waterfront.

Henryk Sadura/ Getty Images

Many booming cities are desperately short of housing and developers are responding with even taller buildings. Many urbanists believe this is a good thing, although studies have shown that life-cycle and operating emissions increase with building height. This is why I have always pitched what I called the "Goldilocks Density," making the case that you can get significant residential densities without tall buildings—just look at Paris or Montreal.

Much of this research was completed before the significance of embodied carbon—or what I prefer to call upfront carbon emissions—was fully understood. These are the emissions released during the materials production and construction phases, in the atmosphere before the building is even occupied. They matter because there is a carbon budget, a maximum amount of carbon dioxide (CO2) that may be emitted to stabilize warming.

As noted by researchers in Carbon Brief, it "originates from the approximately linear relationship between cumulative CO2 emissions and the warming of the Earth that they cause." Every ounce of fossil carbon dioxide added to the atmosphere counts against this budget.

Cover, Buildings for the Climate Crisis

Buildings for the Climate Crisis

A recent study, "Buildings for the Climate Crisis- A Halifax Case Study," looked at new residential developments in Halifax, Nova Scotia, Canada through the lens of embodied carbon. The study was prepared by scientist Peggy Cameron of Friends of Halifax Common and climate consultancy Mantle Developments.

It starts by trying to explain embodied carbon:

"In the building sector, embodied carbon is largely ignored and unregulated due to a focus on operational carbon, but its reduction must be a part of the solution. As operational energy efficiency is a proxy for carbon, retrofits or new builds don’t usually consider embodied carbon in materials used, wasted or land-filled. This omission is preventing us from reaching net zero carbon."

The study found: "Two proposed developments for four high-rise towers in the Carlton Street block will have a huge and unacknowledged cost to the climate, emitting approximately 31,000 tonnes of embodied carbon in global warming emissions or carbon dioxide (CO2e) equivalents. This number does not include the estimated 160T from associated demolitions."

summary of carbon emissions

Buildings for the Climate Crisis

Development Options Halifax, a citizens group, proposed an alternative nine-story infill project that retained most of the existing buildings. Its proposal said:

"This design follows the principle of distributed density; small-scale buildings that fit into empty areas in a city, keeping the existing structural resources and adding to the built environment’s diversity. This mid-rise building option, along with a renovation of the existing historic buildings, will result in approximately 18,000 tonnes of CO2e, which is 40% less embodied carbon emissions/m2 than the proposed new highrises."

Buildings are the carbon they ate

The report includes the latest thinking about embodied carbon, including work by the Architects Climate Action Network (ACAN)—we have covered the network and its work in Treehugger in the past. ACAN notes in the report that "as buildings become more energy-efficient and energy sources decarbonize so the operational carbon is lowered, the relative portion of carbon emissions associated with the embodied carbon becomes increasingly significant." Yet embodied carbon is not regulated and is studiously ignored.

Even the people who write the codes aren't taking it seriously. The Canadian Commission on Building and Fire Codes said that "until all levels of government agree on an approach for a national carbon-freeeconomy, the long-term performance goal for buildings should focus on energy—not carbon." The report correctly notes that this much change and that we need "a measurable commitment to reducing embodiedcarbon in building and construction."

Case study

Buildings for the Climate Crisis

The report then examines two projects, both of which involve the demolition of "missing middle" multiple-unit housing. Having calculated the embodied carbon released to build this project, it tries to explain how much this actually is with the usual comparisons, noting that 31,000 metric tons of CO2e is equivalent to "9,497 passenger vehicles; consuming 13,206,189L of gasoline; 414 tanker trucks of gasoline; 7,260 homes’ energy for one year; consuming 70,041 barrels of oil; or 1,291,667 propane cylinders used for home barbeques."

The report makes the case for reusing, rebuilding, and infilling:

"Assessing the carbon worth or value in existing buildings generally proves that extending their life through retrofitting, renovation, re-purposing, rehabilitation or adaptive reuse is a more cost-effective and sustainable choice when compared to new construction. The Life Cycle Analysis evidence is in—the assumption that building new, more efficient buildings is the only way to address climate change is unfounded. The greenest buildings are already built; it can take between 10-80 years for a new “green” building that is 30% more energy efficient than the existing one to make up for the upfront carbon emissions unleashed during construction."

The report also covers a lot of the ground we have discussed on Treehugger: how taller buildings have higher embodied carbon per unit area. "Ignoring the available evidence on the carbon cost of choosing the wrong building typology is a driving factor in the climate crisis," reads the report. "As noted from the case study, the structural complexity of increasing height causes embodied energy intensity to increase substantially."

The report also notes: "When rising from five storeys and below to 21 storeys and above, the mean intensity of electricity and fossil fuel use increases by 137% and 42% respectively, and mean carbon emissions are more than doubled." With a name like Treehugger, this site is not considered a good academic source, but we have seen a lot of this before.

It then covers the questions of density done right, of distributed density, of the Missing Middle, of how different building forms and typologies can create housing with much lower buildings and less embodied carbon.

Policy guidance

The report concludes with a series of admirable policy recommendations and suggestions. A few of my favorites include:

  • Create a conceptual path forward to regulate embodied and operational carbon emissions in the building and construction industry using a Life Cycle Assessment (LCA) methodology.
  • Include legally-binding targets, year-by-year timelines, policies and accountability measures with audits to achieve net-zero embodied and operational carbon GHG emissions.
  • Develop and enforce scientifically-based, consistent standards on what actually constitutes net zero.
  • Adopt zoning practices, including height restrictions that encourage land use patterns that
    control/reduce/eliminate demolition and increase distributed density.
  • Promote less carbon/resource-intensive, secondary or recycled materials (reduce/avoid
    aluminum, cement, petrochemical-based materials and steel).
  • Set building codes, planning and specification requirements, rules, regulations, taxes, etc. to create incentives for reducing carbon intensity, with sectoral targets for building and construction that include interim two-year targets en route to final goal of 50% GHG reduction
    by 2030—treat carbon like we did cancer-causing cigarettes.
  • Set requirements for product labeling for building and construction materials.
  • Set requirements for the building and construction industry to measure, report and reduce embodied carbon emissions beginning 2022 for building permitting—this is needed to identify opportunities for reducing GHG emissions in the initial phase, develop capacity and assist
    future policy development and standardization.
  • Set strict absolute limits on embodied carbon emissions for all developments by 2024.
  • Set real, legally-binding government targets for net-zero GHG emissions reduction in building and construction sector by 2030, with annual reporting and audits on progress. Make stringent life cycle assessment mandatory prior to issuing building or demolition
    permits with the intent to disincentivize demolitions.
  • Design building codes to transform the building sector, not for minimum standards, that is to
    mitigate emissions, increase resiliency and durability.
  • Require carbon budgets for all renovation or new construction permits at the application stage that includes embodied carbon and operational carbon accounting and targets whole life net-zero carbon.

So what was the response?

As someone who has been writing about this for years, I believe this is a very important report, with excellent recommendations that should be studied by everyone in the business. But I couldn't help thinking about how it would be received. Would it be brushed off as the work of a bunch of NIMBYs or taken seriously?

I asked Peggy Cameron, a scientist and vice president of a renewable energy company, about this and she was blunt, starting by describing her background and credibility:

"I’ve been involved in climate change research and advocacy for decades. My first real immersion was working with a couple of people to develop an educational workshop on climate change for Atlantic Canadian Environment Canada employees. That involved a lot of reading of dense, fact-based climate change science, which in 1999 stunned and scared the bejesus out of me."

A city councilor said she "should stop making things up and stick to the facts."

"People are unaware or in denial. Developers are sophisticated- they hire PR firms, build websites, buy coffee or more for politicians and paradigms often take an abrupt crisis to shift. Like stomach ulcers and h pylori and Nobel prizes."

This is where we are with the issue of embodied carbon and upfront carbon emissions. The Carbon Brief researchers will say:

"For the 1.5C target, we estimate a range of 230-440bn tonnes of CO2 (GtCO2) from 2020 onwards, which corresponds to a two-in-three to one-in-two chance of not exceeding 1.5C of global warming since pre-industrial times. This is equivalent to between six and 11 years of global emissions, if they remain at current rates and do not start declining."

"Buildings for the Climate Crisis" may have bombed in Halifax, Canada, which is going through a development boom and doesn't want to hear this stuff. The report was, as I suspected, seen as a NIMBY effort, and it does come off in places as being anti-growth and anti-development.

But the over-arching theme is we have to deal with the issue of upfront carbon and we have to do this right now. We have to change our building codes, our official plans, and our zoning bylaws to accommodate and encourage low-carbon construction. This report should be studied and its lessons applied in every city—it's Halifax's loss but everyone else's gain.

Download the report at Friends of Halifax Common.

View Article Sources
  1. Matthews, H. Damon, et al. "The Proportionality of Global Warming to Cumulative Carbon Emissions." Nature, vol. 459, no. 7248, 2009, pp. 829-832., doi:10.1038/nature08047