Geothermal systems, green building materials, and flexible design are just a few of the strategies used in sustainable school design.
As a North American industry leader, Graham Construction’s experience in state-of-the-art educational facilities is reflected in its extensive portfolio. In its pursuit of building better, the company’s involvement in mass timber construction further underscores its commitment to staying at the forefront of the industry.
Currently pursuing LEED Platinum and Zero Carbon Building certification, the Lawson Centre for Sustainability at Trinity College, University of Toronto, emphasizes the integration of advanced ecological design principles and cutting-edge technologies to reduce the building’s carbon footprint and optimize energy efficiency.
Sean Carroll, Site Superintendent with Graham Construction, joins us to explore the key sustainable features, materials, and products incorporated into the design and construction of the Lawson Centre.
Build Canada (BC): With the Lawson Centre targeting LEED Platinum and Zero Carbon Building certification, what are some of the key sustainable features, materials, and products being used in its design and construction?
Sean Carroll (SC): The Lawson Centre for Sustainability has aimed for the highest achievable ratings in new green building technologies by targeting both LEED Platinum and Zero Carbon certification through building design, environmentally friendly materials, and sustainable construction methodology. Thermal models and research analysis were completed prior to construction to test high-efficiency systems. The building envelope targets a thermal resistance value of R-37 to R-38 (effective) for the façade, R-40 for standard roofs, and up to R-50 for green roofs, significantly reducing energy demands for heating and cooling.
The building uses enhanced insulation and airtightness to minimize heating and cooling loads, with over 200 mm of insulation and a 40 mm air gap in the walls. Higher roof R-values and a vapour-permeable envelope system allow the mass timber structure to breathe, supporting long-term durability.
A continuous air-vapour barrier (AVB) wraps from the footing base around the entire building to maximize airtightness. Additional features include triple-glazed windows with bird-friendly fritting and an optimized window-to-wall ratio to reduce heat loss while maintaining ample natural daylight.
The concrete used for the project is an environmentally friendly product called EcoCrete. EcoCrete had to meet strict standards to minimize global warming potential (GWP) while still achieving high compressive strength. Through close collaboration with the concrete supplier and several iterations with the structural engineering team, we developed mixes that met both the low-GWP requirements and the necessary strength profiles for the building’s numerous concrete applications. One key trade-off was that the concrete achieved its design strength at 56 days rather than the typical 28.
To accommodate this, the construction schedule was sequenced to allow for longer curing periods. Digital cloud-based thermal couplers were used alongside traditional cylinder break tests at 3, 7, 28, and 56 days to monitor curing patterns. The building façade is clad in locally sourced limestone brick and slabs, reducing embodied carbon associated with transportation and supporting the regional economy.
Geothermal Heating and Cooling
BC: What geothermal heating and cooling strategies are being implemented at the Lawson Centre, and how do they reduce environmental impact compared to conventional systems?
SC: The Lawson Centre includes a designated geothermal field located at the southeast corner of the site, approximately 40 m by 25 m, with 57 boreholes drilled 650 feet deep. The system uses a single-loop geothermal heat-recovery configuration containing 32,500 liters of heating fluid—4,500 liters on the building side (1,125 liters pure glycol) and 28,000 liters on the field side (7,000 liters pure glycol).
This was the first major activity completed on the project. The horizontal loops sit 5 feet below final grade and are located beneath a designated green field area planted with sod and perennial vegetation. The earth maintains a consistent temperature of about 10°C at this depth, and modern heat pump systems leverage this constant temperature for heating in winter and cooling in summer. This eliminates the need for fossil fuels for the building’s primary heating and cooling systems. Natural gas is used only for the emergency generator and two architectural fireplaces in common areas.
The geothermal system works in combination with chilled beam technology, eliminating the need for conventional forced-air heating and cooling. Air handling units are used solely for air balancing, without any gas requirement. This system also provides heat for a strategic snow-melt system around the building’s exterior.
Going Green
BC: How do the Centre’s green roofs, interior green walls, and rooftop Urban Farm contribute to energy savings and support research, education, and community engagement?
SC: As with many dense urban campuses, preserving and restoring green space was a key design priority. Green roofs not only compensate for lost ground-level green space but also significantly reduce energy consumption while mitigating climate impacts. The vegetation and soil layers provide natural insulation, helping keep the building cooler in summer and warmer in winter. This increases the roof assembly’s R-value to approximately R-50. Green roofs also help reduce the Urban Heat Island effect through evapotranspiration—plants releasing moisture that absorbs heat and cools the surrounding air.
The interior green wall serves as both an architectural feature and a contributor to occupant wellness and LEED Platinum certification. Research shows that green walls improve indoor air quality by absorbing carbon dioxide and releasing oxygen, help regulate humidity, and reduce fatigue and illness. They also support mental well-being, creativity, and productivity.
Rain Harvesting System
BC: What are the environmental benefits of the Centre’s rain harvesting and recycling systems?
SC: The rainwater harvesting system significantly reduces demand for city-supplied water—particularly important since toilets account for a large portion of water consumption in modern buildings. With approximately 346 residents and 50 staff, the Lawson Centre’s system captures rainwater, diverts part of it to the municipal storm system, and meters a portion into internal sump tanks and an external box culvert beneath the landscaped common areas. This water is then treated, stored, and reused for toilet flushing and landscape irrigation during dry periods.
Importance of Moisture Management
BC: Since mass timber can absorb water quickly if exposed to standing water, what moisture-management and protection measures were used during design and construction?
SC: Controlling the moisture content of mass timber during and after construction is critical to building performance and long-term durability. Extensive research shows that mass timber must remain within strict moisture thresholds to maintain structural integrity over time. Prior to construction, our team worked with RDH Building Science—North America’s leading mass-timber consultant—to develop a detailed moisture management plan based on industry best practices.
Because our construction schedule extended through winter, we implemented creative solutions to keep progress moving while protecting the timber.
Mass timber is most vulnerable when enclosed—such as during installation of floor toppings (rigid insulation, acoustic mat, and a 3-inch concrete topping) or when CLT floors and walls are encapsulated in drywall. It is essential that timber reach the required moisture content before topping or enclosure and maintain that level afterward.
Key principles included:
- Roof and openings must be fully sealed before pouring any concrete topping to prevent moisture from penetrating the assembly.
- Substrates must be tested to confirm all areas meet the required internal moisture content—typically 16–17% at all depths—before enclosure. We paused work at this stage to document the readings in a “pre-enclosure report,” which included photos and moisture data for every area to be topped or enclosed. This documentation provided critical assurance that the timber assemblies met design criteria before being sealed.
Innovation. Sustainability. Technical Excellence.
The Lawson Centre for Sustainability demonstrates how thoughtful integration of geothermal systems, low-carbon materials, resilient mass-timber construction, and active landscape design can redefine the performance of academic buildings. Graham’s collaborative approach—grounded in innovation, sustainability, and technical excellence—is helping deliver one of Canada’s most advanced low-carbon student residences.
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Original article published by Build Canada Construction Profile Magazine (Nov. 2025)
Coming in 2026!
Lawson Centre for Sustainability (Part Two)
