b'A fact sheet on roof insulation published by Johns Man- However, the designed performance can only be achieved through proper installation. Implementing industry ville (RS-7386) notes that as much as eight per cent of thebest practices, such as the installation of multiple layers with staggered joints, will optimize energy efficiency of thermal efficiency of insulation can be lost through thethe system and will help ensure that the roof system performs during its service life.joints and exposed fasteners of installations that use only aTo learn more about the benefits and uses of polyiso insulation, please visit the Polyisocyanurate Insulation single layer of insulation. Manufacturers Association (PIMA) website at polyiso.org.Marcin Pazera, PhD, is the Technical Director for PIMA. He coordinates all technical-related activities at PIMA Airintrusion:Whenconditionedairentersthebuild-ing envelope, often because of pressure gradients, it car- and serves as the primary technical liaison to organizations involved in the development of building standards. For more ries moisture into the roofing system. This moisture willinformation, visit polyiso.org.undermine optimal performance. A peer-reviewed studyThis article was originally printed in Roofing magazine, and is reprinted with permission. on air intrusion impacts in seam-fastened mechanically attachedroofingsystemsshowedthatairintrusionwas minimizedbynearly60percentwhentheinsulation joints were staggered between multiple layers of insula-tion. (See Air Intrusion Impacts in Seam-Fastened, Me-chanically Attached Roofing Systems, by Suda Molleti, PEng; Bas Baskaran, PEng; and Pascal Beaulieu, iibec.org.) Additionally,bylimitingtheflowofairandmoisturethrough a roof system, staggered layers of insulation in a roof assembly can reduce and/or prevent condensation. The condensed moisture, if allowed to remain and accu-mulate in the system, can damage the substrate and poten-tially shorten the service life of a roof. A properly insulated roof can also prevent the onset of condensation by effec-tively managing the dew-point within the roof assembly. Apeer-reviewedstudyonairintrusionimpacts in seam-fastened mechanically attached roofing systems showed that air intrusion was minimized by nearly 60 per cent when the insulation joints were staggered between multiple layers of insulation.Resilient roof assemblies: Staggered joints can reduce the stress put on a single insulation layer and distribute that stress more evenly over multiple, thinner insulation joints. For example, in an adhered roof system, the installation of multiple layers of insulation can minimize the potential for membrane splitting. In this system, the upper layer(s) of insulation can protect the membrane from potential physical damage caused by fasteners that are used to attach the bottom layer of insulation to the roof deck.Ponding water: Roof slope is often created through the use of tapered insulation systems. These systems offer an op-portunity to stagger the joints by offsetting insulation lay-ers and improve overall energy performance of a system. If the added insulation layer is tapered, the slope provided can improve drainage performance of the roof. Rainwater that does not drain and remains standing, collects dirt and debris that can damage or accelerate erosion of the roof covering. Integrating a tapered polyiso system with stag-gered joints into a roofs design will not only improve the thermal performance but also can improve drainage and thus overall longevity of the system. Puncture resistance: Roof cover boards are commonly installed to provide a suitable substrate for membrane at-tachment as well as protect the roof assembly from punc-ture and foot traffic. When using products like polyiso high-density roof cover boards, the joints should also be staggered with the underlying roof insulation. This ensures the benefits discussed above are preserved in systems uti-lizing cover boards.Installation Best Practices are Keys for SuccessAproperlydesignedroofsystemthatutilizeshigh- performance polyiso insulation products is a strong foundation (orcover)forenergy-efficientandsustainableconstruction. ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 2 201913'