Thermographic Inspections – An Energy Auditor’s Tool

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Thermal Imaging Camera

Infrared scanning, commonly referred to as “thermographic inspections,” detects thermal defects and air leakage in buildings. Through the use of infrared video and still cameras and their images (referred to as “thermograms”), this process:

Measures surface temperatures,
Detects light from the heat spectrum images on the video / film, and
Records variations in temperature in the building’s “skin.

The purpose is to assist the auditor in assessing where insulation is either needed or incorrectly installed.

Types of Thermographic Inspections

Thermographic inspections are categorized as either interior or exterior scans:

Interior scans are the more common ones as warm air escaping from a building rarely move through walls in a straight line.
In detecting heat loss from outside the building, one cannot assume that it originates from a location immediately adjacent to that specific location.
It is also harder to detect temperature differences on the outside surface during high winds.

For these reasons, the interior scans are usually the preferred option. They are generally more accurate and subjected to fewer environmental factors. When combined with a blower door test, these scans provide a clear view of air leaking through the building outer shell.

Thermography is clearly a recommended option in performing a routine energy audit; but should also be used prior to purchasing a new home. Performed by a certified technician, this will provide the purchaser with a clear indication of any defects in a home’s thermal envelope.

Infrared Sensing Devices

There are a number of options regarding devices for conducting an on-site thermographic inspection:

Spot (Point) Radiometers: As the name implies, spot radiometers measure radiation one spot at a time, indicating the temperature at each specific spot and allowing the auditor to note differences in temperature upon panning an area.
Thermal Line Scanners: This device highlights a line scan over an image of a specific area, showing temperature variations along the line.
Thermal Imaging Cameras: Considered the most accurate of thermographic inspection devices, these cameras produce a 2-dimensional image of an area showing heat leakage.

If one is provided a choice, the thermal imaging camera offers by far the best option. The level of detail necessary for a proper home energy assessment cannot be attained using either spot radiometers or thermal line scanners; and conventional cameras are not sensitive enough to detect heat loss.

Achieving Best Results

Timing and preparation are key to achieving the most accurate results:

Furniture should be moved away from exterior walls
Drapes should be removed
Since most accurate images occur with large temperature differences, it is best to conduct these scans in the winter (northern states) and the summer with the air conditioner on (southern states).