O&S Associates, Inc. employs infrared thermography to help detect moisture infiltration and other adverse conditions or deterioration beyond the extent visible to the naked eye.

Infrared Thermography is a non-destructive testing technique performed using a camera that is sensitive to infrared (IR) light instead of visible light.  Infrared is the “light” emitted by thermal energy or “heat”.  This light is beyond the visible light spectrum, similar to how ultraviolet radiation is beyond the opposite end of the light spectrum.  Infrared cameras produce images of invisible infrared or “heat” radiation and capture precise non-contact temperature measurement.  The images obtained are called “thermograms”, which is basically a photograph of infrared light, instead of visible light.

Everything with a temperature above absolute zero emits heat. Even very cold objects, like ice cubes, emit infrared. The higher the objects temperature, the greater the IR radiation emitted.

When a building system is being heated during the day, or cooled at night, each element of that system will heat or cool at different rates based on material properties. Deterioration changes material or system properties therefore thermogram can help identify deteriorated areas in a system under the right conditions.  For example, saturated objects will gain or lose heat differently than un-saturated objects.  A saturated building component, or delaminated component, or other adverse condition will therefore appear anomalous or non-uniform in a thermogram.  Infrared Thermography is therefore helpful for gaining insight into the condition of building elements, or locating areas for additional testing or exploration.

Infrared cameras enable roofing professionals to measure and compare the temperatures of roofing substrate materials that are wet—presumably from leaks, and roofing substrate that is dry. The dry roof areas cool faster after sunset and warm up faster than the wet areas after sunrise. This causes a temperature difference that can be imaged.

The Practice is addressed by the American Society for Testing & Materials (ASTM) in measurement standard C1153, "Location of Wet Insulation in Roofing Systems Using Infrared Imaging."

Water enters the roof system by means of splits, holes or faulty flashing, causing the roofing components (i.e. insulation, felts, decking) to become wet. The wetter areas store more heat from daytime solar loading and remain warmer at night. Reduced thermal value of water damaged insulation and/or decking materials also allows for heat transfer of interior energy through the wet components during the colder months.  It is this thermal radiation of water present in the roof that the infrared camera records. The hot spots are visible on the surface of the roof when viewed through the infrared camera.  Buildings with concrete decks rely mainly on solar loading to heat the roof system, therefore scanning concrete decked roof systems during the winter and roof sections that remain in shadow during the day (below units, overhangs, under gratings, etc.) provide negligible thermal profiles.

Moisture entering the roof system at penetrations and base flashings that does not affect the insulation will not be detected by the infrared camera because the moisture can flow directly into the building interior, leaving the insulation unaffected. This can typically occur at pipe penetrations, pitch boxes, ventilators, mechanical units, skylights and masonry walls.

The roof top is scanned during the evening- shortly after sundown in the winter, and one to two hours after sundown in the summer (these conditions may vary due to the type of roof membrane).  Scanning at night allows for sufficient cooling of the roof surface and eliminates solar reflection resulting in a more accurate scan.

The information can now be presented as colorized thermograms, with different colors or shades representing different surface temperatures.  Variables that can affect the thermal radiation include wind velocity, cloud coverage, and material density.  A color bar along the side of the thermograms indicates temperatures in ascending degrees with warmer areas at the right of the bar (typically the wettest areas in roofing and driest areas in the masonry scan).  Corresponding visible light photographs help to orientate the thermograms, as well as give clues to water entry points.

Please note that the findings can only be accurate and representative for the time of the moisture survey.

• Saturated areas will appear “cooler” if the moisture can evaporate from the object.  This is due to the thermal dynamics of evaporative cooling.
  
  
• Saturated areas where the water is “trapped” will appear “warm” if the environment around it is cooling, since water will lose heat slower than most construction materials.
  
  
• Delaminated objects (objects where a coating, or material layer becomes separated) will appear warmer or cooler depending on the circumstances since the mass at the delaminated surface is less than the mass of the sound surface.