b'STEEP SLOPEvolume is not simple or always practical. Attic Ventilation DiagramHaving Troubleshooting OptionsIna2009American SocietyforTestingand Materialspapertitled Compact Asphalt Shingle RoofSystems:Should They Be Vented, authors Peter E. Nelson and Jason S.DerAnaniannoted, The longevity of the roof assembly also relies on the occupants ability to identify whether leakage or wetting is occurring and to provide leak repair. If the leakage is concealed or unnoticeable, the damage will go undetected.Whilenoonewants something to go wrong inside the attic, the fact is its an application advantage to be able to visually inspect a vented attic for signs of trouble. If spray foam insulation is installed along the underside of the roof deck in an unvented attic, how can a troubleshooting inspection take place? The potential consequences of an undetected leak or moisture problem canbesignificantbothintermsof damage and cost.Year-RoundPerformanceinAllSoffit VentsClimatesShingles that are installed on unvented roof assembles operate at slightly higher temperatures,roughly2-3degrees Fahrenheit warmer than shingles on vented assembles. This can reduce their service life by roughly 10 percent, said Joseph Lstiburek of Building Science Corporation (in the August / September 2011FineHomebuildingarticle,A CrashCourseinRoofVenting).If roofing professionals are not worried about a 10 percent service life reduction, Ridge VentContinued on page 40www.mrca.orgMidwest Roofer 39'