b'Energy LossesConclusionsTask 2 of the industry consortium project, ERCR, quantified theUsing fasteners as an attachment method in membrane roof thermal bridging of fasteners that are typically not considered in the thermal design of roofs. In assessing the impact of thermal bridging, more than 100 experiments were conducted, highlighting the effectassemblies, compared to using adhesives, has multiple benefits: of fastener density, fastener location, fastener diameter and fastener penetration depth on the effective R-value of the roof assembly. Quantifying the effect of fastener density, the measured data in- higher wind uplift resistance, ease of application and faster dicated that thermal bridging increases with the fastener density and with the thermal resistance of the insulation. The average loss in ef-fective R-value ranged from five to 14 per cent. Generalized fastenercompletion of the roof assembly, flexible installation without impact factor curves representing the three design categoriesR-26, R-31 and R-36were developed, which will allow the designer to predict losses for different fastener densities followed in the industryissues of mopping and curing and marginal cost benefits.and design roof assemblies to appropriately accommodate the losses.In a multilayer insulation layout, fasteners installed in the bottom layer are shielded by the top insulation and can reduce thermal bridg-ing from 30 to 70 per cent relative to through fasteners (i.e., fasteners installed on the top layer), depending on the thermal resistance of the top insulation layer. The installation of thicker insulation (higher ther-mal resistance) as the top layer is a preferable design approach. AcknowledgementsThe fastener penetration depth below the steel deck was found to have a minimal impact on the thermal performance of the roof assembly.The authors acknowledge the ERCR consortium members mentioned earlier for their support and ac-The increase in the fastener diameter or the fastener area (#12 tive participation in this project. #14 #15) increased the overall heat flow through the assembly.Dr. Molleti is a research officer in the Performance of Roofing Systems and Insulation (PRSI) Group at From #14 to #15 there was an average eight-per-cent drop in the ther- NRC, where his works focuses on researching the wind-induced effects on low-sloped roofing systems and mal performance, and from #12 to #15, the reduction was 18 per cent. The results are specific to the R-31 assemblies tested. The comparisonthe thermal and hygrothermal performance of roofing systems. He is currently working on establishing of #12 to #14 revealed a decrease of 6.5 to 12 per cent (R-26 to R-31),energy ratings for roofing assemblies, wind performance of vegetated roof assemblies, energy and durabil-showing that the thermal bridging effect increases with the increasingity performance of PV integrated roofs and application of vacuum insulation panels in roofing systems. thermal resistance.He is a member of the ASTM D08 and CRCA Technical Committees. Using fasteners as an attachment method in membrane roof as- Dr. Baskaran is a group leader with the NRC and an adjunct professor at the University of Ottawa. He semblies, compared to using adhesives, has multiple benefits: higher wind uplift resistance, ease of application and faster completion ofis a member of committees at IIBEC, RICOWI, ASCE, SPRI, ICBEST and CIB and a research advisor the roof assembly, flexible installation without issues of mopping andto various task groups of the National Building Code of Canada. He has authored or coauthored over 200 curing and marginal cost benefits. To sustain these benefits, the com- research articles and received over 25 awards, including the Frank Lander Award from the Canadian Roof-mercial roof design should acknowledge the thermal bridging effectsing Contractors Association and the Carl Cash Award from ASTM. Dr. Baskaran was recognized by Her of fasteners and plates and accommodate them appropriately at the design stage of the roofs.Majesty Queen Elizabeth II with a Diamond Jubilee medal for his contribution to his fellow Canadians. Towards codification, efforts are underway to potentially imple-ment these thermal bridging factors in the energy codes to updateReferencesthe current thermal design of roofs, which appear to assume thermalASHRAE 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings. 2013.bridging of fasteners have an insignificant impact on effective R-value.D. Burch, P. Shoback, and K. Cavenaugh. A Heat Transfer Analysis of Metal Fasteners in Low-Slope This enhancement can lead to optimized roofing energy designs, re- Roofs. ASTM International. 1987.alistic prediction of commercial building energy savings and mainte- T.W. Petrie, J.A. Atchley, A.O. Desjarlais, and J.E. Christian Effects of Mechanical Fasteners and Gaps nance of an energy-efficient built environment. Between Boards on Thermal Performance of Low-Slope Roofs. Journal of Thermal Envelope and Building Science. Pp. 23(4): 292-317. 2000.E.K. Olson, C.M. Saldanha, and J.W. Hsu. Thermal Performance Evaluation of Roofing Details to Improve Thermal Efficiency and Condensation Resistance. Roofing Research and Standards Development: 8 thVolume. ASTM STP1590. West Conshohocken, PA. 2015.R. Gulati, S. Suddapalli, and R.S. Srinivasan. Roof Fasteners for Metal Deck Roofing Systems: Energy Impact on Reroofing and Recover Scenarios. Proceedings of the 31st Roof Construction Institute International Convention and Trade Show. Orlando, FL, 2016.M. Singh, R. Gulati, R.S. Srinivasan and M. Bhandari. Three-Dimensional Heat Transfer Analysis of Metal Fasteners in Roofing Assemblies. Buildings. pp. 6(4), 49. 2016.ANSI/SPRI WD-1, WD1Wind Design Standard Practice for Roofing Assemblies. Waltham, MA. 2014.FM Global. Roof Deck Securement and Above-Deck Roof Components. Factory Mutual Insurance Company. 2016.Canadian Commission on Building and Fire Codes. National Energy Code of Canada for Buildings. National Research Council of Canada. 2015.S. Molleti and A. Baskaran. Energy Resistance of Commercial Roofs. ASTM D08 Ninth Symposium Roofing Research and Standards Development. West Conshohocken, PA. 2019.ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus. West Conshohocken,PA, 2019. This article originally appeared in the February 2020 issue of IIBEC Interface. Learn more about the Interna-tional Institute of Building Enclosure Consultants (IIBEC) by visiting their website at IIBEC.org.26ONTARIO ROOFING NEWSISSUE 1 2020 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'