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Zero carbon building is a lofty goal that is often criticized as too difficult to achieve. But the new Forensic Crime Scene facility at Trent University set out to prove that zero carbon building is something we can — and must — do today.
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, pursued by this project, which ensures that a building produces as much energy from renewable sources as it will consume each year. The program also establishes a cap on embodied carbon — the GHGs produced by manufacturing building materials — 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.
Zero carbon building results table

Material carbon emission results from the BEAM tool show that the building has reduced its carbon footprint by 88% from the baseline building.

 

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.

 

Zero carbon building

 

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

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