Winnipeg — Construction practices, policies, building and energy codes and other regulations need to change if Canada is to meaningfully reduce GHGs from the building sector, a new report finds. Emission Omissions: Carbon accounting in the built environment, a new peer-reviewed study conducted by the International Institute for Sustainable Development (IISD), examines Life-cycle Assessments (LCA) — the primary analysis tool used by industry and researchers to account for GHGs and other impacts of building products at each phase of their “cradle-to-grave” lifespan (i.e., production, use, end of life).

The report finds while they are the best-available tool for evaluating GHG performance of alternative building products and designs, current LCAs have limits that may misdirect efforts to reduce GHGs from the built environment – one of Canada’s largest sources of emissions. Major findings include:

LCAs may produce very different accounting of carbon for similar projects because data can be missing, while built-in assumptions and uncertainties are not disclosed.

LCAs do not track or account for “biogenic carbon” from the extraction and end-of-life stages of wood building products. For example, carbon losses related to soil disturbance in logging operations, variable regeneration rates of forests, and conversion of primary to secondary forests are not counted. This may represent up to 70 per cent of total lifecycle emissions. These impacts challenge the prevailing assumption wood construction materials are less carbon intensive than steel or concrete and should be favored.

Existing LCA models may misrepresent embodied emissions from materials, exaggerating their importance while ignoring embodied emissions from other building systems or the contribution of other significant lifecycle emissions, such as from a building’s energy use.

Important regional factors are often overlooked. For example, while production intensities and related emissions can vary significantly from site to site, LCAs typically use average national, continental or global data.

According to the researchers, LCAs need to become more robust and transparent. They should include more data and full disclosure of research assumptions if they are to guide GHG reduction strategies and reduce other environmental harms from buildings and infrastructure. Building efficiency and longevity as well as optimizing material use should also be priorities for decarbonizing the built environment.

The study was commissioned by the Cement Association of Canada and conducted under the guidance of an advisory group comprised of university affiliated academics, notable environmental organizations and architects/designers from the green building community.

The report is available at https://www.iisd.org/sites/default/files/publications/emission-omissions-en.pdf.

A backgrounder is available at https://www.iisd.org/sites/default/files/publications/emission-omissions-backgrounder-en.pdf.

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