Techniques > Energy Conservation >

Thermographic Inspection

Energy auditors may also use thermography — infrared scanning — to detect thermal defects and air leakage in building envelopes. Thermography measures surface temperatures by using infrared video and still cameras. These tools "see" light that is in the heat spectrum.

Images on the video or film 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. They also serve as a quality control tool, to ensure that insulation has been installed correctly.

A thermographic inspection is either an interior or exterior survey. The auditor decides which method would give the best results under certain weather conditions.

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, interior surveys are generally more accurate, as they benefit from reduced air movement. Thermographic scans are also commonly used with the blower door is 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 view finder.

Most energy audits take from four to eight hours and cost between $300 and $500. Any retrofit work would of course cost additional money.

Home Energy Audits, EREC Reference Briefs, Office of Energy Efficiency and Renewable Energy, US Department of Energy