ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWS – ISSUE 1 2026 17 Contrary to the initial expectation that these lower-embodied-carbon materials might increase overall construction cost, contractor bids collectively reflected significant project cost savings compared to the base design. membrane and two new 6.35-mm (0.25-in.) asphaltic overlay boards – the first layer mechanically fas- tened to separate the new and old system, and the second adhered to reduce risks with fastener backout below the membrane. Crucially, this scenario incorporated a “re- surfacing” strategy for subsequent roof renewal cycles, where only a one-ply cap sheet membrane would be installed at 20-year cycles, with no further material removal, significantly reducing future impacts. One initial roof re-cover and two resurfacings were assumed over 60 years. It should be noted warranty options are avail- able with select manufacturers. Scenario 3 (Roof Re-Cov- er/Renewal V.2 [Embodied Carbon Optimized]): Similar to Scenario 2 in its re-cover ap- proach, this scenario specifically selected lower-embodied-carbon materials. Instead of two layers of asphaltic board, it specified a base sheet membrane panel (a mem- brane laminated onto an asphaltic board) and a 6.35-mm (0.25-in.) gypsum overlay board. This sce- nario also assumed one initial re- cover with optimized materials and two subsequent resurfacings over 60 years. Similar to Scenario 2, warranty options are available with select manufacturers. The results from this large in- dustrial warehouse study provid- ed powerful validation. Embodied Carbon and Waste Reduction Compared to the baseline full- roof replacement (Scenario 1), the roof re-cover options demonstrat- ed significant embodied carbon savings (also see Table 1): Up-Front (Initial Restora- tion) Carbon Savings: Scenario 2 (Roof Re-Cover/ Renewal): A seven-per-cent reduction in up-front (life-cycle modules A1-A5) embodied car- bon (from ~2,020,000 kg CO2 eq. [4,453,338 lb CO2 eq.] to ~1,880,000 kg CO2 eq. (4,144,691 lb CO2 eq.]). Notably, the study revealed that these initial savings were not as high as initially expect- ed, primarily due to the relatively high embodied carbon content of the multiple asphaltic overlay boards. Scenario 3 (Optimized Roof Re-Cover/Renewal V.2): A 24-per-cent reduction in up- front (life-cycle modules A1-A5) embodied carbon (to ~1,520,000 kg CO2 eq. [3,351,026 lb CO2 eq.]). Most of the up-front em- bodied carbon savings (~90 per cent) was from the base sheet panel, with the gypsum board providing lower embodied carbon savings (~10 per cent). Full-Life-Cycle (60-Year Study Period) Carbon Savings: Scenario 2 achieved a 55-per- cent reduction in embodied carbon (from ~6,060,000 kg CO2 eq. [13,360,012 lb CO2 eq.] to ~2,720,000 kg CO2 eq. [5,996,574 lb CO2 eq.]). Scenario 3, with its optimized material choices, delivered an even greater 61-per-cent reduc- tion (to ~2,360,000 kg CO2 eq. [5,202,909 lb CO2 eq.]). This was largely driven by the “resur- facing” strategy for future cycles, which resulted in a 75-per-cent embodied carbon intensity re- duction compared to repeated full replacements. Avoided Waste: Both re-cover scenarios (2 and 3) diverted approximately 480 tonnes (529 tons) of up-front construction waste from land- fills. Over the full 60-year life cycle, this figure soared to an esti- mated 4,200 tonnes (4,630 tons) of waste diverted. Unexpected Cost Savings Taking these principles fur- ther, we applied embodied carbon optimization on a large industrial warehouse roof by developing an alternate design that prioritized lower-embodied-carbon materi- als with EPDs. Instead of the typ- ical two layers of asphaltic board, the design specified a base sheet panel – a membrane laminated onto an asphaltic board – for the first layer and roof-grade gypsum board replacing the second as- phaltic board layer (Scenario 3). The base sheet panel and gypsum board both have a higher material
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