Renewal Strategies for Low-Slope Ventilated Wood-Framed Roofs
Abstract
Roof ventilation requirements are firmly established for residential wood-framed buildings, with ventilation commonly considered beneficial for providing drying, reducing cooling loads, minimizing ice dams, and extending the service life of roof materials by reducing surface temperatures. However, growing evidence of mold growth, moisture accumulation, and deterioration of low-sloped wood-framed roofs in the Pacific Northwest has initiated an ongoing debate regarding prescriptive venting requirements. Of particular interest is how to improve durability of roof assemblies as part of renewals work, but current guidance for the design, construction, and renewal of roof assemblies is primarily anecdotal.
The objective of this paper is to highlight the findings of a significant research study and subsequent design guideline development conducted in British Columbia, Canada. This study and guide development includes a survey of roof conditions during renewals, monitoring and testing, hygrothermal and energy simulations, and an industry guide. The work focuses on identifying key factors impacting the observed performance of these roof assemblies, and subsequently developing design solutions. The potential benefits of adding insulation above the roof deck, sealing of roof vents, and increasing airtightness are examined. This paper is intended for designers, researchers, contractors, manufacturers, and building owners to increase awareness of newly available guidance for the renewal of low-sloped wood framed roofs.
