Published: Jan 1999
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Hygrothermal performance describes the response of the material layers that make up the wall to thermal and moisture loads. Modelling can be applied to determine the drying and wetting potential of walls with various initial construction moisture loads and to test alternative innovations. This paper investigates the drying performance of a particular barrier EIFS clad wall as a function of vapor diffusion control with a specific air leakage path. This investigation was conducted with constant interior temperature and relative humidity.
The LATENITE model, developed at NRC, is employed in the investigation. This advanced hygrothermal model can incorporate system and sub-system performances by introducing simulated defects and wall system details derived from laboratory and field measurements. Moisture loads available to the EIFS structure originating either from the interior, the exterior or from initial construction moisture can be included.
In this paper the authors present a study to determine the drying potential of a barrier EIFS clad wall for the climate of Wilmington, NC. This climate is characterized by the ASHRAE Handbook of Fundamentals as being mixed. The effect of drying and wetting by airflow was investigated by introducing airflow paths. Hygrothermal performance with three differentvapor diffusion control strategies and two air leakage conditions was simulated for a period of one year. Initial oriented strand board (OSB) moisture content was assumed to be very high. The influence of rain water, solar radiation and air movement within the cavity was included in the analysis.
Results showed that the vapor control strategies were an important parameter dictating the drying performance of the particular barrier EIFS clad wall. Air leakage through the building wall system was also found to have a significant effect. Proper EIFS performance analysis must include both vapor and liquid diffusion control mechanisms, initial conditions, air leakage, climate, material and system and sub-system characterization. This investigation showed the importance of the vapor diffusion control strategy and air leakage on the hygrothermal drying performance of a particular barrier EIFS clad wall with a specific air leakage path.
air leakage, moisture analysis, modeling, exterior insulation finish system (EIFS), vapor retarder, drying potential, moisture transport, hygrothermal performance
Research Officer, National Research Council Canada (NRC), Building Envelope and Structure, Ottawa, Ontario
Research Scientist, VTT, Building Technology, Building Physics, Espoo,