b'windows and balconies in our build- Understanding the Loadsings,whichcomplicatedesignandWhen we are considering how air detailing. Excellence in architectureacts on our buildings, it is important requires balancing aesthetics and hu- to understand the sources of air pres-man elements with the requirementssure:windeffect,stackeffectand forengineeringaseparationthatmechanical effect.works in all conditions. Wind is created by the solar heat-Thank God for building scienceing of one area of the earth opposed thescientificknowledgeandex- toanother,inwhichthewarmer perience that focuses on the analysis(higher pressure) air moves up into and control of water, air, heat andtheatmosphere,drawingcooler radiation in the built environment.(lowerpressure)airwithitand Professionallyappliedbuildingsci- across the surface of the earth. These ence provides predictive capabilitiescells are globally distributed and re-to assist in mitigating the risks asso- sponsible for much of our prevailing ciatedwiththebuildingenvelope,winds. Storms that produce intense while also optimizing the life cyclewindsareasimilar,microversion, and performance of building com- which have other factors, but tem-ponents and assemblies. perature differences are a key driver Thebuildingenvelopecanbein wind development. Wind will try imaginedasaballoonthatenve- to go right through a building in its lopes all sides of the building. Likepath; at this point, it becomes a bat-a blown-up balloon, it separates ortle of strength as wind either passes controls in part: bulk water, air pres- through the weak points of a build-sure, water vapour and temperatureing envelope or is redirected aroundFigure 2: Mechanically attached single-ply membrane without air and vapour barrier. Illustration courtesy of GAF.(although briefly). When haphazard- the building, creating a whole salad ly sealed or penetrated, the buildingof new loads and wind speeds.envelope fails to perform. This mayStack effect is also due to differ-seem like an oversimplification, butentialairtemperature,butacross thekeep-it-simpleapproachhasthebuildingenvelope.Whenthe never been more important when itair within a building is warmer and comes to building assemblies. Poorlymore buoyant than the air outside, designedandconstructedbuildingthe more buoyant air will rise to the envelopes are at best inefficient andtopofthebuilding,muchlikeoil uncomfortable, and at worst can leadin vinegar. This buoyancy will exert outwardpressureonthebuilding to premature material and assemblyenvelopeathigherelevationsand deterioration. The failures associatednegativepressureatlowereleva-with the building envelope will be intions. There will be a zone halfway direct correlation with the work thebetweenthesetwopointswhere envelope is expected to perform, sothepressurewillbeneutral,called itisimportanttounderstandthetheneutralzone.Thestackeffect worktheenvelopedoes.Forthis,will increase based on the height of we first need to consider the loadsa building and can become almost that are present in the environmentunmanageable,capableofintenseFigure 3: Roof section with fully adhered air and vapour barrier at structure. Courtesy of GAF.(Figure 1). physicaldamage.Since 1935 Serving the roofing industry since 2005 withSimple to installRoofing & Sheetresponsive and dependable service and advice. pre-grown modular Metal Contractors vegetated roof systems Re-Roofing SpecialistsThe Fenn & Fenn Roofing Insurance Program Maintenance & Repairs General Liability and Excess Liability Insurance including Hot WorksIndustrial & Commercial Business Property Insurance Builders Risk, Contractors Equipment & Wrap Up Liability InsuranceAutomobile FleetContractors Pollution Liability InsuranceEasy Certificate of Insurance Programme saves time Contract Surety (Bonding)Exceptional Service and contract risk and insurance adviceITS THE WORKMANSHIPFenn & Fenn Construction Practice, a THAT COUNTS division of Hub International Ontario Ltd.220 Norseman St., Tel:(905) 836-6066Toronto, ONM8Z 2R4 Toll Free:(866) 269-8799Tel: 416-239-3594Fax: 416-239-9891 70 Main Street St. S. liveroof.cajseeback@seeback.com Newmarket, ONL3Y 3Y6 519-671-5777www.seeback.comORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 4 2023/2421'