Persistent elevated amounts of moisture within building materials and components can lead to issues with mold growth and lessen structural integrity of the building. Moisture surveys are used to determine relative amounts of moisture in specific building areas and components such as exterior wall cavities and roof assemblies, including the insulation. They are also a useful tool in determining the cause and origin of potentially damaging water infiltration.
Non-destructive means of investigation such as infrared scanning thermography, using an infrared camera, and impedance testing are initially utilized when performing a moisture survey. An infrared camera is used to detect temperature differences within a building component or assembly. As such, infrared scanning is most effective at sunset or at night. It is at these times that exterior surfaces cool more quickly as the outside air temperature decreases while areas where moisture is present, such as materials and insulation, have a larger thermal mass and thus take much longer to cool. Infrared scanning is also an efficient way to help locate hidden moisture issues that often go undetected. Impedance testing uses a measuring instrument which emits low frequency electronic signals from rubber electrodes. When scanning over dry substrates, the electrodes are insulated from one another and a complete circuit is not made, thus resulting in little to no readings for moisture. Conversely, when an impedance meter is scanned over a wet substrate, the electrical conductance is greater, resulting in a more complete electrical circuit and the readings are increased. The greater amounts of moisture result in higher readings.
Often, small limited areas of destructive testing can be performed to serve as confirmation of the findings from the non-destructive testing methods of a moisture survey. When destructive tests are performed, they are as non-invasive as possible and taken at a variety of areas, including those that were determined earlier to be dry and at areas of differing moisture content.