While discussions to reduce operational carbon emissions work their way through provincial and federal building code development processes, embodied carbon remains harder to pin down and ranks lower among regulatory targets.
However, municipalities are demonstrating they can provide leadership.
Take Toronto as an example. In May, the city upgraded its Toronto Green Standard to TGS version 4. Included in the new provisions are whole-building embodied carbon caps on new city-owned facilities. That makes Toronto the first jurisdiction in North America to take such definitive action.
“New city-owned buildings must now be constructed with lower carbon materials and ensure their upfront embodied emission intensity associated with major structural and envelope materials is below 350 kg CO2e/m2,” writes Toronto energy efficiency consultancy Mantle Developments. They note at the present time, these caps cover major structural and envelope materials, although policies may expand to other portions of a building life cycle.
The TGS v4 consists of three tiers of performance measures, the city explained in a media release.
“Tier 1 is mandatory through the planning approval process. Tiers 2 and 3 are higher level voluntary standards associated with financial incentives verified post construction.
Toronto is proud of its standing as a leader in sustainable new construction.
“Since its introduction in 2010, the TGS has resulted in annual GHG emissions reductions of 169,383 CO2e (carbon dioxide equivalent), which equates to taking 52,000 cars off the road every year,” the city says.
In fact, the TGS v4 goes beyond the tracking of building materials. Not only does it call for newly constructed city buildings to be net-zero, TGS v4 provisions also call for electric vehicle charging in parking spaces and enhanced storm water management and landscaping requirements.
Up to 80 per cent of upfront embodied carbons occurs pre-occupancy but can be fully managed through lower carbon decisions in design, procurement and construction, Mantle writes.
On the other hand, “Post-occupancy embodied emissions associated with the use phase (B) and the end-of-life phase (C), although essential to manage long term, are a lesser source of embodied emissions, are spread over many decades, and involve much uncertainty since future assumptions are required.”
Past study of embodied carbon in construction leads Mantle to conclude the construction industry already acknowledges the availability of low-carbon materials in the Toronto market.
“Industry leaders have noted experience of around 30 per cent embodied carbon reductions are easily achievable without major changes to design or primary structural material.”
Therefore, switching to them would result in little impact on either project cost or schedule.
The City of Toronto is not finished addressing embodied carbons. Future versions of the TGS will be released in 2025 and 2028. By 2028, the city will mandate very low emissions in buildings by requiring all new development to meet what is now the highest tier of performance.
“Looking ahead, TGS v4 and future versions that come into effect in 2025 and 2028 will result in 30.5 metric tonnes of cumulative emissions reductions by 2050, which equates to removing more than nine million cars from our roads,” it says.
Toronto is putting its shovels where its standards are, announcing a new affordable rental housing project in the downtown, designed to the highest tier of TGS v4 using MTC and other low-carbon materials.
With no onsite fossil fuel and maximizing onsite renewable electricity, the result will be a near-zero GHG emissions structure. This project joins a number of other new municipal projects with zero emissions objectives, including a community centre, a child care facility and a paramedic station.
Mantle advises the construction industry to be prepared for the next level of the TGS v5 that will likely contain a broader application of mandatory embodied carbon caps.
“Developers and construction material manufacturers would be wise to expect similar mandatory low-carbon design and materials requirements on private buildings soon. Developers take note: the time is now to develop a low-carbon materials strategy and inform your design and procurement teams that lower embodied carbon is a priority.”
John Bleasby is a Coldwater, Ont.-based freelance writer. Send comments and Climate and Construction column ideas to email@example.com.