b'Technical ArticleAir BarrierDesignin Roofing By Paul JohannessonS o you thought air leakage wasit is paramount that we pay attention just a wall thing? Nope, its ato and become familiar with all of whole building thing. Air canthe environmental factors that affect leak into and out of a building onthe built environment; after all, the allsixsides,andfailingtoaddressbuilt environment exists to separate this fact in your design and detailingus and protect us from the extremes canhavenegativeeffectsontheof the outside world.performance and life cycle of your buildings. Leaks in foundations andThe Environmentfloorscanallowwater,radongasThe built environment exists to and volatile organic compounds toprotect us through separation from enter. Leaks in walls and windowsournaturalenvironment.Itsepa-can draw water into the assemblies,rates us from other people, weather whereitcancausedamagetoevents,generalclimateconditions, buildingmaterialsandcausemoldsolar radiation and sound. Some ex-growth.Uncontrolledairleakageamples of our built environment are can reduce occupant comfort whileneighbourhoods, homes, workplac-negativelyaffectingairqualityandes,schools,shops,parksandplay-energy efficiency.grounds. The challenge in separating Air leakage in roofing assembliesourenvironmentisthat,although can ultimately result in catastrophicwe mostly want separation, we also roof failures affecting the building,want connectionsometimes at theFigure 1: Air infiltration and exfiltration. Illustration by Morrison Hershfield Corporation, courtesy of Building Science Basics.contents and inhabitants. Therefore,same time. This explains the need for 20ONTARIO ROOFING NEWSISSUE 4 2023/24 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'