b'Energy-RCI: A web tool for the thermal Technical Articledesign of commercial roofsBy Sudhakar Molleti, Logan Carrigan and Helen YewFigure 1: Decrease in thermal resistance as a function of fastener density using #14 fastener. Note: 1 m 2= 10.8 ft 2 .The following article originally appeared in IIBEC Inter-face and is reprinted with permission. Figure 3: After assigning a project name the user selects an energy code and E nergy-RCI is a National Research Council (NRC)Figure 2: Unit selection screen. enters location information, leading to the automatic generation of thermal Canadawebapplicationtooldevelopedforthedesign requirements. Note: U-Value = U-factor.thermaldesignofcommercialroofs.Availableat https://nrc.canada.ca/en/research-development/prod-ucts-services/software-applications/energy-rci, the aim of Energy-RCI version 1.0 is to provide design solutions for thermal bridging of mechanical fasteners in roof thermal performance. This paper seeks to briefly explain the func-tions and capabilities of Energy-RCI and how it benefits the Canadian and U.S. roofing industries. Additionally, the existing web-based applications are briefly compared.Development of the Energy-RCI Web ToolBuilding energy codes, such as ASHRAE 90.1, 1,2the International Energy Conservation Code 3and the National EnergyCodeofCanadaforBuildings(NECB), 4 provide minimum performance requirements for designing ener-gy-efficient building systems, including roofing systems. However, these codes and standards have mainly focused on the insulation requirements and placed less emphasis on thermal impact factors such as thermal bridging and thermal bypass and their effects on energy loss. Figure 4: Selecting a roofing system type.Thermal bridging occurs in roof assemblies in areas where the uniform thermal resistance of the assembly is changed by the inclusion of materials with relatively high-er thermal conductivity, such as the mechanical fasten-ers. For example, in low-slope membrane roofing systems, mechanicalfastenersareusedtosecuretheindividual components and provide resistance against wind uplift forces. The three standard roofing system types that fall into this category are the mechanically attached roofing system (MARS), partially attached roofing system (PARS) and induction welded roofing system (IWRS). The num-ber of fasteners or fastener density in each system depends primarily on the required wind uplift resistance that the system must sustain to meet the prescribed design loads.Currently, in the roofing industry, documents such as ANSI/SPRI-WD15and FM 1-29 6provide performance-basedfastenerdensitiesformechanicallyfastenedroof assemblies.Forassemblieswherethesecriteriaarenot specified, fasteners can be added prescriptively or based on specifications from roofing manufacturers. Based on current industry practice, the fastener densities in MARS, PARS and IWRS can range from 0.15 to 1 fastener per square foot (1.6 to 10.8 fasteners per square meter). How-ever, the thermal bridging resulting from these fastener densities is not currently addressed in the thermal designFigure 5: Selecting the membrane type and cover board.of roof assemblies.20ONTARIO ROOFING NEWSISSUE 1 2022 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'