Infra-red vs. Capacitance Moisture Surveys

N. American Roof Management Services is capable and qualified to provide non-destructive testing utilizing either infra-red thermography or capacitance based technologies which can be used separately or in tandem.  

Infra-red thermography does not actually detect moisture but rather uses an infra-red camera operated at night to detect heat loss in a roof system.  Through daytime solar gain, insulated roof systems containing either wet or dry insulation absorb heat. However, due to its greater thermal mass, areas of roof containing moisture laden insulation take much longer to cool versus areas containing dry insulation. It is this difference in emitted thermal radiation which can be detected by the infra-red camera. 

Capacitance technology emits electronic signals and directs them towards the roof surface.  When conducted over a roof system containing both dry insulation and roofing felts, no readings are registered as the low frequency electronic signals are insulated from each other.  However, the presence of moisture will complete an electronic circuit and generate readings that increase with the extent of roof system moisture content.

The electronic moisture detection instrument generates two low frequency electronic signals. It transmits these signals through parallel electrodes located in the bottom of the unit. By moving the unit across a roof's surface in a regular pattern, (covering every square foot), any areas of roof that contain moisture can be readily identified.

It is important to note that water is a good conductor and that the electrical resistance in non-conductive insulating materials will vary inversely with their moisture content. The unit can be adjusted to one of three sensitivity scales depending upon the type of roof system being surveyed.

Essentially, by surveying a roof surface with the unit, the presence and extent of moisture within the roof system can be detected. Once the presence of moisture has been verified by means of physical test cuts, the extent of the area containing moisture can be outlined both on the roof surface and of course on a roof drawing.