Innovation-July-August-2023

CHALLENGES IN BUILDING LOW-CARBON

emissions savings. “Hempcrete’s insulative properties allowed us to design a different kind of passive cooling system, where we didn't need high carbon mechanical equipment to cool our building,” noted Mollard Thibault. The team estimates that using electric heating mats instead of a hydronic radiant with heat pump led to a 75.9 kgCO 2 eq reduction in emissions. While hydronic radiant systems are operationally efficient, electric heating mats use less concrete and piping, leading to savings in embodied carbon. Other changes for efficiency, including a waste heat-recovery ventilator and a demand-control ventilation system that automatically adjusts airflow rates depending on the house’s detected carbon dioxide levels, lowered operational and embodied emissions. Together, they made Third Space Commons “essentially carbon free from the mechanical system,” according to Alex Mitro, P. Eng., who oversaw the project’s mechanical system.

to grade individual pieces and test them for structural integrity. “We just didn't have the time or resources to pay a structural engineer to look at each piece of wood and say 'Yes, you can use it for this function,'” said Mollard Thibault.

One of Flores Pitton’s main roles was to reduce the embodied carbon in the building’s foundations. The team decided to implement steel helical piles, a foundation-building method that they projected would emit less embodied carbon than a standard concrete foundation because of their high reusability at their end of life. Helical piles disrupt a smaller volume of soil during construction and cause minimal disruptions to the surrounding natural environment. The minimized soil displacement is especially relevant from the lens of a full life cycle assessment, where the relocation of excess soil for a concrete slab foundation would contribute significantly to emissions. However, much of Vancouver is considered a high seismic zone, which meant that stronger lateral resistance was required. The piles and superstructure of the house were ultimately reframed, increasing the projected carbon emissions of the project beyond initial expectation. “I don't think any of us even had an inkling of an idea of how complex it would be,” said Third Quadrant’s architectural captain, UBC Master of Architecture student Katie Theall. Ultimately, the team realized that the best way to create a low-carbon building was to reuse material. Mollard Thibault noted, “That means taking pieces out of buildings being demolished or using construction waste from inefficient construction sites that are going to go to landfill.” The main pitfall of reusing material is that the process requires extensive amounts of time and labour. To reuse wood, a structural engineer would need

TQD team members Juliette Mollard Thibault, right, and Agustina Flores Pitton review inside the living lab. P hoto : W endy D photography

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