Is Climate Emergency Incentive Enough?
Our team at Builders for Climate Action (B4CA) has been coalescing since 2019 with the idea of bringing a strong, data-driven understanding of the full carbon footprint of buildings to the industry and to help facilitate a transformation to carbon storing buildings in an equitable world.
There has always been an urgency to this work, and our ambitions have increased from simply drawing attention to embodied carbon to fully advocating for carbon storage. In July this year, the urgency increased with the release of the IPCC Working Group’s new report which is, according to UN Secretary-General António Guterres, nothing less than "a code red for humanity. The alarm bells are deafening, and the evidence is irrefutable".
At B4CA, we know there is some good news here in the construction sector: we have the ability to stop creating emissions and making carbon storing buildings today—at least in the low-rise sector—and that we can accelerate the pace of getting all buildings to at least zero carbon emissions and then to net carbon storage.
But there’s no time to dawdle. This will take our full attention as an industry. Regulators need to first encourage and then enforce real zero carbon limits. Manufacturers need to engage in full transparency and move forward with innovations in low-carbon and carbon-storing products. Designers need to understand how to reduce and reverse emissions in their buildings through climate positive design and material selection. Builders need to procure low-carbon and carbon-storing materials and understand how to install them properly. And citizens need to demand that all of us adhere to an ambitious schedule.
Unlike many other sectors, a climate-positive construction industry need not fear for its very existence. We need buildings, we need to renovate older buildings, and we can do all of this while reversing our climate impact.
Do any of us have anything better to do? Let’s get to work!
Trent University Forensic Crime Scene Building is a Zero Carbon Leader
To date, most efforts to achieve zero emission buildings have focused on operational emissions. Such is the case with the International Living Future Institute’s Zero Carbon Certification, which ensures that a building produces as much energy from renewable sources as it will consume each year. The program also establishes an embodied carbon cap of 500 kg CO2e/m2 and a reduction of embodied carbon by at least 10% from a base case scenario.
Endeavour Centre joined Trent’s design team for the project to create a new teaching facility for their Forensic Science department, and was able to use the BEAM tool to establish that a base case scenario for this building would come in with a material carbon footprint of 498 kg CO2e/m2, just under the maximum threshold for the Zero Carbon Certification.
But the team had much higher aspirations than just getting under the wire. The intent was to design a building that stored as much carbon in its materials as was emitted in making all the materials, and ideally getting the project into net carbon storing territory.
To that end, each material was examined in BEAM to understand the emission implications. The materials with the highest impacts in the base case scenario were targeted for improvement or replacement.
Exterior walls moved from CMU with spray foam insulation to hempcrete blocks and hemp batt insulation; concrete for the slab and foundation was specified for the highest amount of slag to replace Portland cement; attic insulation moved from mineral wool to cellulose and; sub-slab insulation became foam glass gravel instead of XPS foam.
These choices, among other smaller modifications, enabled the building to get very close to zero net embodied carbon. In total, these changes reduced over 185 tonnes of total carbon emissions, with the building having a minimal carbon intensity of just 60 kg CO2e/m2.
The estimation above did not include any carbon storage in the timber products in the building, which included wall, roof and floor framing and the charred wood siding. After securing local and/or certified wood for the project, we calculated the carbon storage using the methodology and calculator from World Wildlife Fund’s Biogenic Carbon Footprint Calculator for Harvested Wood Products. This tool does more than just reckon the actual amount of carbon atoms in wood, but accounts for carbon emissions and forest regrowth to come closer to a real understanding of the climate impact of using different types of wood products. It’s not a perfect methodology (much work is being done in the sector to close in on a better understanding of forest carbon flows), but we used it as the best available and transparent resource available. With a percentage of the wood carbon storage recognized, the Trent Forensic Crime Scene facility tips over into net carbon storage.
In addition to material choices, the design team pursued a high degree of energy efficiency, with insulation levels upgraded (R-100 attic, R-42 walls, R-28 foundation and slab) and a highly air-tight enclosure (meeting the Passive House requirement of 0.6 ACH50). Heated and cooled with an air source heat pump and with a 43 kWh solar array on the roof, the building has very low energy consumption requirements and is able to meet these on an annual basis with on-site generation.
Trent University and the design team achieved a unique result: a real zero carbon footprint building, or as close to the goal as is possible with today’s data and materials.
With the exception of the solar array and its attendant gear, the costs associated with the project were within the typical range for an institutional project of this type. Enough carbon storing materials were available in the market to allow the project to meet its goals. Material sourcing, supply chains and construction experience with new materials were obstacles that this team was able to overcome, but provide insight into the pinch points that currently may prevent more projects of this type from being realized.
The barriers to creating buildings with a true zero carbon footprint are low enough that we should be pursuing this type of result as the new normal, and not only on one-off projects.
This project was made possible by a great design team:
Architect: Christopher Z. Tworkowski Architect
Contractor: Gerr Construction
Mechanical: ZON Engineering
Electrical: Berthelot Engineering
Structural: Building Alternatives
Zero carbon consultant: Endeavour Centre