Passive Infrared Thermography—A Qualitative Method for Detecting Moisture Anomalies in Building Envelopes

The presence and detection of moisture in building envelopes may best be described as an elusive phenomenon in a heterogeneous medium. When normal (parabolic-shaped) moisture content gradients exist in the material or when the material is uniformly equilibrated, traditional moisture instruments (conductance and dielectric types) perform adequately. However, these instruments may not be ideally suited to cope with a wet building envelope anomaly that can change its shape, location, and content as conditions dictate. Infrared thermal imaging is a more versatile tool for in-situ moisture detection because it can rapidly scan a surface to determine if irregular thermal patterns, "thermal anomalies," are present that suggest an excessive moisture condition. Investigations of moisture intrusion through the masonry-veneer envelope of a commercial and a residential structure are presented, as well as the resultant microbial colonization in the interstitial wall space. An infrared inspection was performed in accordance with International Standard ISO 6781-1983 (E) using a FLIR Systems Thermovision® 550 infrared imaging system. Based on a qualitative interpretation of the thermal scans, wall areas were selected for invasive examination and correlated with moisture-meter readings. The masonry veneer was removed to expose the method of brick installation and the composition of the envelope. In addition, the interstitial wall cavity of the commercial building was inspected from the interior using negative air pressure glovebag containment. Observations were photographed and the free water content of building components was measured. Microbial colonization of the interstitial wall space was observed and, in some cases, with deteriorating building components. Air sampling for culturable fungi was conducted three times over a 2-year period in the commercial building to determine whether fungi that were present in "visually inaccessible spaces" migrated into the occupied space. These investigations demonstrate that qualitative infrared thermography coupled with an informed visual inspection and quantitative substantiation using moisture meters is an effective method to detect moisture anomalies in building envelopes.