b'UNVENTED WOOD ROOFof the unvented puzzle begin to professionals with appropriate knowl- published, without specifics as to the fit together.edge and installed by builders withhome or owner. Under such assumptions, it is possibleappropriate qualifications. Re-roofing occurred in 2022 when the to achieve the desired result throughThe unvented roof is now one of home still incorporated a vented roof. computer modelling of complextwo acceptable solutions under Part 9,At the time, the homeowner paid a physical phenomena. Unvented roofingwhich are deemed by the province premium to install a continuous self-can achieve acceptable performanceto be equivalent and used at the adhering underlay below the shingles. commensurate with that of venteddiscretion of the builder without The underlay is common in wood-roofing, particularly in that it will resistprofessional involvement.framed roofing but is usually limited to the tendency to accumulate mois- Equality, at least for the moment,the bottom three feet of a steep-slope ture over time. So, when you set up aremains elusive, and it is having shingle roof.computer program with assumptionsconsequences for at least one In this case, the homeowner installed that ignore some fundamental realitieshomeowner already. the membrane over the entirety of the of construction, like failure of a roofroof below the shingles. Given the membrane and wetting of a woodUNVENTED CONVERSIONvented construction when the roof went roof deck, you can arrive at just aboutCAUSES DAMAGE TOon, this vapour barrier was not expected whatever result you desire. In most ofTWO-YEAR-OLD to have adverse effects as drying could Canada, licensed and regulated profes-sionals are required to make the call asSHINGLE ROOF occur to the attic and through the to whether the assumptions are valid. This summer, I was engaged to reviewnumerous roof vents present.Thus, qualified professionals can justifya curious issue on a wood-framedTwo years later, the homeowner decided the use of an unvented roof assemblysteep-slope roof in a single-familyto undertake a far more substantial inte-in a wood-framed building, therebyresidence. The homeowner reported andrior renovation. The entire house was utilizing the out clause in Part 9.provided images of buckling two-year- vacated, and exterior walls and ceilings Up until 2022, this was the processold shingles, which had shown up forwere stripped down to the studs from in Alberta, and it still is throughoutthe first time this summer during thethe inside. The roof sheathing, two-year-most of Canada if you wanted to usehottest part of July. I was surprised toold shingles and underlay remained. In an unvented roof in a wood home.uncover that the cause of the issue wasdeveloping the design for the renova-Professionals performed calculationsthe conversion from a vented roof to antion, the homeowner established the specific to your building using the envi- unvented one. I should take a momentgoal of substantial energy improvements ronmental conditions of the area andto note that the homeowner has agreedand consulted a qualified energy advisor made certain assumptions regarding thefor the details in this article to beon the best approach. The advisor was quality of the construction. They stated those assumptions and designed accord-ingly. Unvented roofing, therefore, was always an exception to the rule, to be specified after careful consideration by PHOTO 1: STEEP SLOPE ROOF, RIDGING CLEARLY VISIBLE IN SHINGLES FOLLOWING THE RAFTERS. PHOTO 2: ATTIC SPRAY FOAM CONVERSION.14 BCBEC ELEMENTSA BCBEC PUBLICATION'