| Abstract | This paper investigates the role of the vapour barrier in a wood-frame stucco wall with the help of two dimensional hygrothermal simulation tool, hygIRC-2D, developed at the Institute for Research inConstruction of the National Research Council Canada. For this purpose, the wall is subjected to theexterior weather conditions of Vancouver, Canada. Three different interior climatic conditions and sevendifferent vapour diffusion strategies, generated by varying the water vapour permeance of the vapourbarrier, installed outboard of the interior finish, have been considered in this study. The outputs from the simulations have been analysed with the help of a novel moisture response indicator called RHT index. Simulation results indicate that the vapour permeance characteristics of the vapour barrier, in terms of water vapour permeance, plays a very important role in the overall moisture response of the wood-frame stucco wall. A very high or low vapour permeance of the vapour barrier does not produce the optimum moisture management strategy for the wood-frame stucco wall subjected to a climate as exists in Vancouver, Canada. Moreover, simulation results indicate that the removal of vapour 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 board. It has also been observed from the simulation outputs that the optimum vapour diffusion strategy, that of limiting the vapour permeance of the vapour 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 vapour barrier in wood-frame stucco wall construction. |
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