Hygrothermal Analysis

The movement of heat energy and moisture through materials and enclosure assemblies can under particular conditions result in performance concerns such as moisture-related issues (e.g., condensation, water damaged materials, reduced R-values, corrosion, freeze-thaw damage) and occupant discomfort. Hygrothermal analyses use the principles of psychrometrics and physics to evaluate the anticipated heat and moisture transport through building enclosure materials. The experience and knowledge gained from hygrothermal analyses enables FCG to provide expert interpretation of the modeled response of individual assembly components to heat and moisture. Our understanding of the model results can be used to identify potential performance risks and guide detailing and materials specifications for the building enclosure.

FCG performs one dimensional hygrothermal models (such as manual and transient calculations), which can often be conducted relatively quickly, can yield valuable information about the performance of the building enclosure. Manual calculations are steady state (i.e., do not account for time-dependent changes in ambient conditions) and usually represent worst-case design conditions. Conversely, transient studies consider both heat and moisture over time. For transient analyses, FCG utilizes WUFI Pro. While WUFI Pro does not inherently consider the effects of air movement, FCG has supplemented WUFI’s simplified approach to consider its effects in all climates. Using the data output from the WUFI Pro program, FCG will interpret and compare the results with the acceptance criteria published in the applicable ASHRAE 160 Criteria for Moisture-Control Design Analysis in Buildings as well as commonly accepted maximum moisture contents of the materials being analyzed.

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