Final Report from Task 8 of MEWS Project (T8-03) - Hygrothermal Response of Exterior Wall Systems to Climate Loading: Methodology and Interpretation of Results for Stucco, EIFS, Masonry and Siding-Clad Wood-Frame Walls

By 1997, several field surveys in North America had indicated that rain penetration in exterior walls and poor construction detailing contributed to the shortening of the service life of recently built exterior walls of low-rise buildings in climates with high exterior moisture loads. There was a movement in industry to rethink the ways that exterior walls had been put together in recent years, as well as a renewed appreciation that exterior climates vary in severity from one location to another. In 1998, IRC/NRC initiated a research consortium with industry partners to develop guidelines for moisture management for exterior wall systems (MEWS) in low-rise residential buildings of North America. Partners represented the wood industry, manufacturers of cladding systems, insulation materials and water resistive barriers as well as building owners and managers. The project was broken down into several tasks, from a review of literature on current construction practice to experimental work in the laboratory and mathematical modelling. The following four types of cladding systems were included in the project: Portland cement plaster (stucco), Exterior Insulation and Finish Systems (EIFS), masonry and siding, over wood-frame construction.This TG8 report is a research document. The objectives of the report are three-fold: to describe the research approach in some detail (chapter 1), to summarize its application to the four types of wall assemblies (chapters 2 - 5) and to draw general conclusions (chapter 6), based on the observations in chapters 2 - 5. The reader is strongly advised to consult the research team before the information presented in this report is used for building design considerations.En 1997, plusieurs \ue9tudes men\ue9es sur le terrain en Am\ue9rique du Nord indiquaient d\ue9j\ue0 que la p\ue9n\ue9tration de la pluie dans les murs ext\ue9rieurs et les d\ue9tails de construction inad\ue9quats contribuaient \ue0 r\ue9duire la vie utile des murs ext\ue9rieurs de construction r\ue9cente des immeubles de faible hauteur dans les r\ue9gions o\uf9 les charges d'humidit\ue9 ext\ue9rieure sont \ue9lev\ue9es. Il y a eu dans l'industrie une tendance \ue0 repenser les fa\ue7ons dont les murs ext\ue9rieurs avaient \ue9t\ue9 construits au cours des derni\ue8res ann\ue9es et \ue0 accorder une nouvelle importance aux variations r\ue9gionales des conditions climatiques. En 1998, l'IRC (CNRC) a mis sur pied un consortium de recherche avec des partenaires de l'industrie pour \ue9laborer des lignes directrices sur le contr\uf4le de l'humidit\ue9 dans les murs ext\ue9rieurs (CHME) des immeubles d'habitation de faible hauteur en Am\ue9rique du Nord. Parmi nos partenaires, nous comptons des repr\ue9sentants de l'industrie du bois, des fabricants de rev\ueatements ext\ue9rieurs, de mat\ue9riaux d'isolation et de mat\ue9riaux hydrofuges ainsi que des propri\ue9taires et des gestionnaires immobiliers. Le projet a \ue9t\ue9 divis\ue9 en plusieurs t\ue2ches, allant d'une revue des documents sur les m\ue9thodes de construction courantes au travail exp\ue9rimental en laboratoire et \ue0 la mod\ue9lisation math\ue9matique. Quatre types de rev\ueatements \ue9taient vis\ue9s par le projet: pl\ue2tre de ciment Portland (stuc), syst\ue8mes d'isolation et de finition ext\ue9rieures (SIFE), ma\ue7onnerie et bardage sur ossature en bois. Le rapport du GT8 est un document de recherche. Le rapport a trois objectifs: d\ue9crire en d\ue9tail la d\ue9marche de recherche (chapitre 1), r\ue9sumer l'application de la recherche aux quatre types de murs (chapitres 2 \ue0 5) et formuler des conclusions g\ue9n\ue9rales (chapitre 6) \ue0 partir des observations des chapitres 2 \ue0 5. Nous conseillons au lecteur de consulter l'\ue9quipe de recherche avant d'utiliser l'information contenue dans le rapport pour la conception de b\ue2timents.Dr. Michael A. Lacasse: https://orcid.org/0000-0001-7640-3701Dr. Michael A. Lacasse: https://orcid.org/0000-0001-7640-3701Peer reviewed: NoNRC publication: Ye