Roof Recovery & Embodied Carbon Material Selection

Title: Roof Recovery & Embodied Carbon Material Selection

Award Category: Roofing

Project Address/Location

255 Chrysler Drive

Woodbridge, Ontario L6S 5Z7
Canada

Submitted By: Milirsan Pugalendiran

Company Info

WSP Canada Inc.

25 York St

Toronto, Ontario M5J 2V5
Canada

6476801848

[email protected]

Project Description and Background: The facility at 255 Chrysler Drive is a one-storey industrial warehouse with two office pods, totaling approximately 1,075,610 sq. ft., managed by Oxford Properties Group. The original built-up roofing (BUR) system had reached the end of its service life, with multiple leaks. Oxford sought a solution that would extend roof performance, reduce cost and waste, and minimize embodied carbon—while maintaining operations in a high-traffic logistics environment. Oxford has partnered with WSP for over five years on national building enclosure consulting services. WSP was selected as Building Envelope Consultant (BEC) for this project based on its delivery of over 30 successful roofing projects and a highly technical team with multiple IIBEC designation holders and active committee participation. For previous Oxford projects, WSP implemented roof recovery strategies—preserving serviceable layers such as coverboard, insulation, and air/vapor barriers instead of full tear-offs. This approach reduces cost, waste, and disruption while maintaining performance. Oxford identified several site-specific constraints: -Continuous truck traffic and limited staging areas. -Strict dust and debris control due to food handling operations. -Rooftop communication systems integrated with lightning protection. -Corporate sustainability goals focused on landfill diversion and carbon reduction. -Budget limitations requiring cost-effective solutions. WSP previously pioneered embodied carbon calculations on an Oxford roof recovery project—one of the first known efforts to integrate such analysis into existing building restoration. This work earned 2nd Place at the Carbon Leadership Forum Toronto’s 2024 Embodied Carbon Awards and was a finalist for PEO’s 2025 Engineering Project of the Year. These accolades inspired Oxford to expand the concept. For this latest project, WSP aimed to elevate the design approach, addressing operational constraints while achieving measurable embodied carbon improvements.

Scope: To address Oxford’s budget, schedule, and sustainability objectives, WSP was tasked with assessing existing conditions and developing design options that balanced performance, cost, and environmental impact. Given the client’s operational constraints and corporate carbon reduction goals, WSP focused on roof recovery strategies rather than a full tear-off and replacement. Roof recovery allows for the salvage of serviceable layers—including coverboard, insulation, and air/vapor barrier—minimizing waste and cost while reducing embodied carbon. Although this approach presents unique challenges, WSP’s extensive experience with similar projects positioned us to deliver an optimized solution tailored to Oxford’s needs. The strategy also aligned with Oxford’s broader ESG commitments and operational continuity requirements. ________________________________________ Diagnostics & Existing Conditions A comprehensive, tiered assessment program was implemented to confirm feasibility and mitigate risk: -Drone-assisted infrared thermography to identify thermal anomalies across the roof surface. -Exploratory openings to verify assembly build-up and validate moisture content at suspect areas. -Moisture meter readings to quantify saturation levels and identify areas requiring localized replacement. -Targeted under-deck inspections to assess steel deck corrosion and determine if repairs or rust-inhibiting coatings were needed. -Strategic cuts at parapets, joints, and penetrations to document air/vapor barrier (AB/VR) discontinuities requiring reinstatement. This multi-layered diagnostic approach ensured that recovery was technically viable and aligned with long-term performance goals. ________________________________________ Design Development Following confirmation that roof recovery was feasible, WSP developed three design scenarios for embodied carbon analysis, all based on 2-ply modified bitumen membranes for their proven durability, client familiarity, and ability to support future resurfacing (which further supported long term lower embodied carbon intensity): Scenario 1 – Full Replacement : Complete tear-off and installation of a new 2-ply modified bitumen system, repeated on a typical 20-year cycle. Scenario 2 – Standard Recovery (Baseline, previously completed at other Oxford properties by WSP): Salvage serviceable layers, install asphaltic recovery board, reinstate AB/VR continuity, and plan future resurfacings instead of repeat tear-offs. Scenario 3 – Enhanced Embodied-Carbon Recovery: Builds on Scenario 2 with selective material substitutions to maximize embodied carbon savings without compromising performance or warranty compliance. ________________________________________ Life Cycle Analysis (LCA) & Decision Tooling To guide material selection, WSP conducted an EPD-first Life Cycle Analysis for each scenario, prioritizing manufacturer-specific and industry-association Environmental Product Declarations (EPDs). A custom Excel-based embodied carbon calculator enabled component-level comparisons across the full LCA boundary—A1–A5 (upfront), B1–B5 (use/maintenance), and C1–C4 (end-of-life). WSP uploaded all available manufacturer and industry available EPDs onto the calculator so that we may toggle different roofing components to produce the lowest embodied carbon system (see images of the calculator under supporting documents). This analysis revealed that two targeted substitutions—gypsum overlay boards and laminated base sheet panels—delivered disproportionately large carbon reductions without relying on niche materials, ensuring constructability, cost efficiency, and alignment with Oxford’s sustainability goals. It is important to note we were using 'low embodied carbon' marketed products. The goal was to achieve the lowest embodied carbon intensity with readily available products with proven performance and no associated premiums which may come with low embodied carbon marketed products.

Solution: While roof recovery offers significant sustainability and cost benefits, it also introduces unique risks. WSP implemented a series of measures to mitigate these risks and ensure long-term performance: ________________________________________ Risk Mitigation Strategies • Material Salvage Validation: To accurately identify wet roofing components concealed beneath the existing membrane, WSP conducted a drone-assisted infrared (IR) scan, validated by exploratory openings, visual inspections, and moisture meter readings. This approach minimized unnecessary material removal while reducing the risk of leaving water-saturated components in place. • Steel Deck Corrosion Control: Corrosion is most likely where wet insulation is present. WSP specified localized deck exposure in areas of moisture intrusion and performed under-deck inspections to confirm structural integrity and determine whether rust-inhibiting coatings or partial deck replacement were required. • Air/Vapor Barrier Continuity: Weak points in the AB/VR system—such as joints, perimeters, and penetrations—were confirmed through exploratory openings. The design included localized self-adhered AB/VR reinstatement at all upturns, expansion joints, penetrations, and perimeters to reduce air leakage, improve energy performance, and enhance roof durability. • Conduit Protection: To prevent accidental damage to live conduits during construction, the contractor was required to map conduit locations from the interior and transfer this data to the roof surface prior to work commencement. ________________________________________ Embodied Carbon Optimization Using WSP’s custom Excel-based embodied carbon calculator, the team evaluated multiple roof configurations and manufacturers. Rather than assigning a blanket embodied carbon intensity to a 2-ply roof system (which commonly done in the industry), we analyzed component-level variations, comparing different component technologies (e.g gypsum vs asphaltic overlay lay) and different manufacturers. This analysis revealed that two targeted substitutions delivered significant carbon savings without compromising compatibility or warranty compliance: • Gypsum overlay boards in place of asphaltic cover boards. • Laminated base sheet panels in place of the second asphaltic board layer. ________________________________________ Selected Solution & Results The chosen design—Enhanced Embodied-Carbon Recovery (Scenario 3)—was selected for its balanced performance, constructability, and sustainability profile, validated through diagnostics and LCA. Key Outcomes: • 61% life-cycle embodied carbon reduction compared to roof replacement(ECI: 61 → 24 kg CO₂e/m²). • ~3.7 million kg CO₂e avoided. • ~4,200 tonnes of life-cycle waste diverted (~480 tonnes upfront). • $6.1M in total client savings compared to full replacement, and 2–3% savings compared to standard recovery and 26% savings compared to a full roof replacement. ________________________________________ Cost Efficiency Insights Although gypsum boards and laminated base sheet panels have higher material costs, competitive tendering across six contractors for three separate warehouse buildings revealed overall cost savings. This was an unexpected surprise for our team. Further investigation revealed the following contributing factors: • Economies of scale: Very large roof areas enabled contractors to negotiate favorable pricing with suppliers. • Labour efficiency: Larger panel sizes (3’×8’ base sheet panels and 4’×8’ gypsum boards vs. 4’×5’ asphaltic boards) significantly reduced installation time, particularly given the low penetration density at 255 Chrysler. This provided the client with a 'no-brainer' choice when selecting one of the three (3) design options. The client chose to proceed with scenario 3.

Value: The involvement of WSP as the Building Envelope Consultant (BEC) was instrumental in delivering a solution that balanced performance, cost, and sustainability while meeting Oxford Properties’ operational and corporate objectives. Our team’s expertise and innovation added value in the following ways: ________________________________________ 1. Breaking the Cost Barrier for Low-Carbon Design A common misconception in the industry is that sustainable design inherently increases costs. Through rigorous embodied carbon analysis and cost benchmarking, WSP demonstrated that employing recovery strategies coupled with strategic material substitutions—such as gypsum overlay boards and laminated base sheet panels—can significantly reduce embodied carbon without increasing overall project costs. Results: • 61% life-cycle embodied carbon reduction • 2–3% cost savings compared to standard recovery • 26% cost savings compared to full roof replacement ________________________________________ 2. Driving Industry Awareness and Innovation This project challenges the status quo by proving that embodied carbon strategies are not limited to new construction. Existing building projects represent a massive, untapped opportunity for carbon reduction. By integrating embodied carbon considerations into a large-scale roof recovery program, WSP set a precedent for the industry and issued a call to action for other IIBEC professionals to innovate in this space. We hope through our IIBEC and BSAO technical articles other IIBEC consultants consider embodied carbon as part of their projects. ________________________________________ 3. Aligning with Client Sustainability Goals Oxford has ambitious landfill diversion and carbon reduction targets aligned with global Net Zero 2050 commitments. Our approach directly supported these goals while maintaining roof durability and energy performance, strengthening client trust and positioning WSP as a strategic partner rather than a technical service provider. ________________________________________ 4. Demonstrating Scalability and Impact The methodology developed for this project is highly scalable. With Oxford alone, WSP's cumulative impact on past roof recovery projects is significant (summarized below): • Five completed buildings: ~1,000 tons of landfill waste avoided and ~850 tons CO₂e avoided (equivalent to the carbon sequestered by ~40,000 trees over 10 years). • Three planned renewals: ~970 tons of landfill waste avoided and ~760 tons CO₂e avoided (equivalent to ~38,000 trees over 10 years). Extrapolated across the hundreds of millions of square feet of industrial roofing in North America, this approach has the potential to transform embodied carbon management in existing buildings. ________________________________________ 5. Importance of IIBEC Member Involvement The technical rigor and innovation required for this project were made possible by a team of IIBEC-certified professionals actively engaged in industry committees. Their expertise ensured compliance with best practices, optimized constructability, and maintained warranty pathways while introducing novel sustainability measures. This project exemplifies how IIBEC members can lead the industry toward smarter, more sustainable building envelope solutions. ________________________________________ Conclusion This project represents a significant step forward in sustainable roof management, proving that embodied carbon reduction can be practical, scalable, and economically viable. By combining technical excellence, cost efficiency, and sustainability leadership, WSP transformed a routine roof renewal into an award-worthy innovation, paving the way for a more sustainable future in building enclosure design.

Project Images

Additional Info: Our team believes our innovative project represents the future of building enclosure consulting and embodied carbon practice. If there are any questions or comments, please do not hesitate to contact our team and we will be happy to clarify or provide additional information for your review.

Documents