b'PHOTOVOLTAICS InstalledInorUnderRoof Decking).Theto keep the roof in optimal condition.(Canada).Fourcommonmethodsare Canadian Electrical (CE) Code, Part I, isMembraneflashingoncurbs,penetra- usedtosecureaPVarrayonaroof: years behind on this subject. For more ontions and around perimeters should bewith ballast, by direct attachment to the this subject see Section 2.7, Electrical Cableseasy to reach and repair. Panels shouldbuilding structural elements, by bonding and Boxes in any of the RoofStar Guaranteebehighenoughabovethefinishedor clamping the PV array support struc-Standards for waterproofing systems forroofsurfacetopermitaccesstothetures to the roof system, and by a hybrid standards and guidance on this subject. membraneandelevatedsufficientlytomethod that (usually) combines a form Designing for safe maintenance promote air circulation between the arrayof structural attachment and ballast. In and the roof. If a low-profile PV array isthis article, well focus on the first three.Roofs require maintenance, and so dodesirable, expect that roof repairs mayBallasted(Figure1),non-pene-photovoltaicarrays.Designingaroofrequire dismantling part of the PV array. tratingPVsecurementiscommon, and photovoltaic system requires carefulPrimaryroofdrainsmustbeandballastingmethodsarenearlyas thoughtaboutthemaintenanceneedsexposed and accessible for routine main- varied as the racking systems available of both. tenance. Ensure that overflow drains areinthemarketplace.SomePVracking Safeaccessandegressarecrit- not blocked by ballast systems used tosystems utilize gravel ballast, but many ical.Iftheroofisntaccessiblefromhold down the PV array. And whereverincorporate proprietary weights. Others a walk-out door, locate a hatch on themaintenanceisrequired,protecttheuse vegetated roof systems for ballast. roof; place the hatch a safe distance frommembranewithsacrificialmembraneVegetatedRoofSystems(VRS)can the roof edge, design it with sufficientpliesorspecifymoveablewalkwaybe a great asset on the roof, absorbing height (at least 200 mm above the top ofpads (rubber pads and concrete paversheat energy; this protects the membrane the roof system) and ensure the hatchon pedestals are common). Alternatively,from premature heat aging. But the VRS is properly guarded. If possible, designdesignconstructedduckboardwalk- must be designed to inhibit root damage access to the hatch so that it opens awayways supported on freely draining padsandpromotegooddrainageandmust from the roof edge, not toward it. or blocks. utilize engineered growing media (dont Design for fall protection. A PV-freeuse systems that incorporate topsoil, fallprotectionzonearoundtheroofSecuring the PV array which will inevitably leach out fine mate-perimeter will help keep workers awayAnything that is attached to or supportedrialsandplugcriticaldrainagelayers). from the roof edge. Higher parapets canbyaroofmustcapablyresistdeadFormoreaboutVRSandRoofStar serve as permanent guardrail around theloads, live loads (for example, wind andGuaranteeStandards,refertoPart14 perimeters and might permit a narrowersnow) and seismic loads. This includesTHE ROOF as a PLATFORM in any of perimetermargin,whichmeansmorerooftop PV arrays, which are addressedthe waterproofing standards for roofs.roofspaceforpanels.However,tallintheStructuralCommentaries(UsersStructuralattachmentreliesona parapets may add to construction costsGuideNBC 2015: Part 4 ofDivision B)direct connection to the building struc-and shade portions of the PV array, andforthe2015NationalBuildingCodeture. This means the roof system carries may increase wind loads on the PV array (a reverse effect expected for an exposed roofsurface).Ifshadeisaconcern, considershorterparapetsandengi-neered guardrails mounted on the inside face to allow more sunlight through to the perimeter panels. Sometimes,foraestheticorother reasons,parapetsandguardrailsare undesirable.Strategicallyplacedfall protection anchors can provide a viable alternative. Bear in mind, however, that engineeredoptionslikefallprotection anchors require ongoing recertification to meet occupational safety regulations. This can turn out to be a burdensome expenseforanowner.Decidewhat mattersmoreanddesigntheroofto achieve the best cost-benefit balance. Accesstotheroofsurfaceis important, too. As roofs age, they will requireinspectionandintervention www.rcabc.org l29'