b'Clean Energyd edge of adjacent 1 array or roof edged d d21 1 unexposed panels: E = 1.0d exposed panels: E = 1.52 row of d 0.5h and d1 max(4h ,1.2m)panels 12d max(4h ,1.2m)22d2d1Figure 2: Definition sketch of exposed and unexposed panels in a roof-mounted solar array (NBC User Guide)and push them inward from theStep 5: Calculate the Netposed solar panels in Step 4, SteprooftopscanbeclassifiedintoproperlydesignedPVsystem edges. Similarly, the wind tunnelDesign Pressure 5calculatestheroof-mountedfour primary types: couldundergofailures(seeFig-data also revealed that an increasesolar panels net design pressure.-ballastedsupportstructureure 3) such as flipping or sliding in the panel chord length has alsoCombiningtheinputsfromFigure 2 provides the definitionrackingsystemsupportedbyofpanels,slidingofthearray, increasedthewindload.SinceStep 1 to 4, the net design pressurefor exposed and non-exposed so- ballast, modules disengagement from the for solar is calculated as follows:lar panels on the rooftop. -fixedorpenetratedsupportracking and clamp disengagement the pressure-gust coefficients areIn the ongoing code develop- structureracking system me- betweenthemodulespuncture generally applicable to shelteredmentsfortheupcoming2020chanicallyfixedtothestruc- of the roofing membrane. When solar panels, they need to be ad- NBC,aproposedcodechangetural deck, thesekindsoffailuresoccur,it justedforarrayedgeconditions(PCF1143)hasbeenapproved-weldedsupportstructureshould be seen as a clear warning (E),parapetsize( p )andchordDepending on the edge factor,to introduce provisions for roof- racking system attached to theof the missing link between the length ( c ), as shown in Step 4. E, used for exposed and non-ex- mounted solar panels in the nextroofmembranebyhot-air- strength (design load) and capac-edition of the National Buildingwelded flange, and ity (resistance) of the PVRA rather Code. These provisions are based-hybrid systemracking systemthan assuming that these failures supported by a combination of on material from the Structuralballast and penetrated supportare the outcome of highly unusu-Commentaries(UsersGuidestructure. al wind events.NBC2015:Part4ofDivisionCurrently,therearenostan-B).Theapprovalofthispro- All of these attachment meth- dardized test methods that deter-posed change will ensure that theodshavedifferentimplicationsmine the collective performance buildingstructuresdesignwillconcerning the wind performanceofthePVRA.Theexistingtest include the additional loads fromof the roofing assembly. First, themethods either focus on PV mod-the roof-mounted solar panels. ItPV systems load transfer to roofules electrical and durability or a will also facilitate code enforce- assembly affects the roof assem- simple static load method to test ment in their design. blyswaterproofing,durability,the racking system. Here is a snap-thermalandstructuralintegrity.shot taken from the Structural En-Wind Pressure ResistanceAndsecond,thefailureofthegineers Association of California of PVRA PVsystemunderwindloads(SEAOC) PV2 document Wind damagestheroofassembly.For Thereareseveraldifferentcommercial roofs to successfullyDesign for Solar Array that high-typesofPVinfrastructuralsys- accommodate as a support plat- lights the importance of a dynam-temsforlow-slopecommercialform for solar arrays, it is criticalic test method to understand the rooftops,producedbyvariousthatadditionaltechnicalaspectsactual behavior of roof-mounted manufacturers.Thesesystemsof the combined PV system andsolar panels: For example, we are are differentiated by the type ofroofassembly,PVRA,mustbenot aware of any research that defines frameworkusedtosupporttheconsidered rather than as separatea relationship between the wind loads modules and mechanisms used toentities. This will ensure the long- calculated in this report (for structur-hold them to the roof. In general,term performance of the PVRA. al design of the racking system) and the PV infrastructural systems onUnderwindaction,anim- the loads used in static loading tests 26ONTARIO ROOFING NEWSISSUE 2 2021 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'