The design choice for any wall system must be integrated with some moisture engineering analysis. Energy and durability analysis must go hand and hand to provide buildings with good service life performance. Moisture engineering analysis has recently been performed to predict whether a particular wall system may survive repeated exterior or interior environmental loads, some of these loads may be intentional and some not. In wood elements mold growth may occur when high moisture content conditions are maintained within the material for a sufficient period of time favorable for biological activity. The appearance of mold in construction materials and the mechanics of mold growth are dependent on a multitude of factors, some not yet fully understood even among wood-durability experts. During the past few years better models have appeared that predict the transport of heat, air and moisture transfer. These models include the important transport processes which allow building envelope designers methods to predict the response of an envelope system to exterior and interior excitation. One of the most important of the exterior environmental loads are those imposed due to wind-driven rain. Indeed, these loads may be many times more important than those due to vapor and air convection transport. To date the winddriven rain loads are possibly the least understood and they can influence the moisture and energy performance the building envelope the most. In this preliminary study, the influence of timeaveraging of the exterior wind-driven rain loading will be examined using advanced hygothermal modeling. The influence of one weather location was examined to determine the effect of local climate on the time-averaging effects on the envelope performance. Experimental data will be analyzed to provide the effect of rain profiling on the transient wetting dynamics of porous facades. Four time averaging step were employed at 5 min, 15 min, 30 min and 1 hour, and these were obtained from experiments. The response of the envelope wall system was evaluated by determining thehygrothermal performance of the structure to dry out as a function of various wind-driven rain profiles. It is expected that the preliminary results from this critical parametric analysis will provide a very useful and fair approach for assessing building envelope wind-driven loads. For the wall cases examined, the choice of hourly weather data is an acceptable time scale for hygrothermal simulation in a defect free wall structure.
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