What's an Infrared Inspection?

Energy auditors may use thermography””or infrared scanning””to detect thermal defects and air leakage in building envelopes.

How Themography Works

Thermography measures surface temperatures by using an infrared camera to see light that is in the heat spectrum. Images record the temperature variations of the building's skin, ranging from white for warm regions to black for cooler areas. The resulting images help the auditor determine whether insulation is needed or where the building envelope is leaking. They also serve as a quality control tool, to ensure that insulation has been installed correctly.

Interior scans are more common, because warm air escaping from a building does not always move through the walls in a straight line. Heat loss detected in one area of the outside wall might originate at some other location on the inside of the wall. Also, it is harder to detect temperature differences on the outside surface of the building during windy weather. Because of this difficulty, interior surveys are generally more accurate because they benefit from reduced air movement.

Insert IR Photo

Thermographic (IR)scans are also commonly used with a blower door running. The blower door helps exaggerate air leaking through defects in the building shell. Such air leaks appear as black streaks in the infrared camera's viewfinder.

Infrared scanning allows energy auditors to check the effectiveness of insulation in a building's construction. The resulting thermograms help auditors determine whether a building needs insulation and where in the building it should go. Because wet insulation conducts heat faster than dry insulation, thermographic scans of roofs can often detect roof leaks.

In addition to using thermography during an energy audit, homeowners should have a scan done before purchasing a house; even new houses can have defects in their thermal envelopes. You should recommend to home buying clients to include a clause in the contract requiring a thermographic scan of the house as part of the inspection. A thermographic scan performed by a RESNET Certified IR Technician is usually accurate enough to use as documentation in court proceedings.

Source: U.S. Dept. Energy

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