ABSTRACT
This paper summarizes a study of combined heat and moisture transfer in sample fiberglass insulation boards using both experimental measurements and numerical modeling. Special attention is given to the conditions where moist air passes through the insulation, simulating air leakage, with a sub-freezing temperature boundary condition at one side of the insulation board. Measurements include temperature, moisture content, air flow rate through the insulation and heat flux with the temperature range from 20 °C to −20 °C. The effects of air exfiltration and infiltration on the heat and moisture transport characteristics within a medium density fiberglass insulation material are investigated. The experimental results, which are typical of cold climate building envelope applications, indicated that for all of the air exfiltration tests carried out, the majority of the moisture and frost accumulation was within the insulation slab adjacent to the cold surface. For air infiltration, it was discovered that the drying rate was substantially higher for lower airflow rates. The numerical results agree reasonably well with the experimental results for exfiltration cases. For infiltration, a relatively large discrepancy between prediction and test data exists. It is expected that thermal instability, because the thermal gradient is opposite in direction to the moisture gradient, is partly responsible for this discrepancy.
