STP1519: Role of Vapor Barrier in Wood-Frame Stucco Wall in Various North American Climates: Observations from Hygrothermal Simulation

    Mukhopadhyaya, Phalguni
    Associate Research Officer, Institute for Research in Construction, Ottawa, Ontario

    Ping, Fang
    Associate Professor, Hunan University, Hunan,

    Kumaran, Kumar
    Principal Research Officer, Institute for Research in Construction, Ottawa, Ontario

    van Reenen, David
    Technical Officer, Institute for Research in Construction, Ottawa, Ontario

    Pages: 20    Published: Jan 2010


    Abstract

    This paper investigates the role of the vapor barrier in exterior wood-frame stucco walls with the help of a two-dimensional hygrothermal simulation tool, hygIRC-2D. For this purpose, the wall is subjected to the exterior weather conditions of six different North American geographic locations and three different interior climatic conditions. Seven different vapor diffusion strategies, generated by varying the water vapor permeance of the vapor barrier, installed outboard of the interior finish, have been studied to generate critical understanding on the role of vapor barrier in the wood-frame stucco walls. The outputs from the simulations have been analyzed with the help of a novel moisture response indicator called RHT index. Simulation results indicate that the vapor transmission characteristics of the vapor barrier, in terms of water vapor permeance, play a very important role in the overall moisture response of the wood-frame stucco wall. A very high or low vapor permeance of the vapor barrier does not produce the optimum moisture management strategy for the wood-frame stucco wall. Moreover, simulation results indicate that the removal of vapor barrier from the wall system can result in a heightened moisture response and a considerable accumulation of moisture in the interior gypsum board that may lead to severe consequences in particular, the premature deterioration of the interior facing gypsum board. It has also been observed from the simulation outputs that the optimum vapor diffusion strategy, that of limiting the vapor permeance of the vapor barrier, is not a function of interior climatic conditions considered in this study. It is hoped that the results reported in this paper will shed some light on a number of concerns raised in recent years on the role of vapor barrier in wood-frame stucco wall construction.

    Keywords:

    vapor barrier, water vapor permeance, wood-frame stucco wall, exterior climate


    Paper ID: STP49035S

    Committee/Subcommittee: C16.30

    DOI: 10.1520/STP49035S


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