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Building Insulation Inspections, Part 2

More and more people are getting into using thermography for building insulation inspections. Unfortunately, many either buy the wrong imaging system—some of the very low cost ones simply don’t have either the resolution or thermal sensitivity required—or fail to get adequate training. BOTH are a mistake! While inspections seem easy, most often they are not.

Industry standards suggest inspections should be conducted from both sides of the envelope. The best imaging, however, is typically from inside where there are fewer variables. On the exterior, the wind, sun and thickness of the siding often make life challenging for the thermographer. For example, brick facing and vinyl siding will both mean inside work.

When the sun shines on the building, it heats up so quickly that exterior viewing is impossible. As a general rule of thermography, however, work does not need to be done at night, but you may need to be inside. Even on the inside, to be successful you must pay attention to where the sun has been. Its effects often will be seen on the inside of the building, 2-6 hours after the wall has been warmed on the outside. This can be very confusing until you understand the direction of heat flow that may have been changed or intensified by the sun.

With care and experience, inspections can be done throughout the year in most parts of the country. Clearly, winter offers the greatest temperature difference in many regions, but don’t avoid the height of summer—just watch out for the sun! In the spring and fall, early morning often offers the best opportunity, but don’t ignore a warm afternoon either. When outside conditions are not ideal, change the inside conditions by turning on the HVAC system. The blower door helps in almost all cases any time of the year.

This image was taken on a cool summer morning. The sun had been shining on the lower part of this wall, but the top was shaded by an overhang. Two hours later, this is the pattern that showed up inside! The wall is insulated. Using thermography may require you to become a “Thermal Sherlock Holmes!”

Get started with optimum conditions, but then don’t be afraid to push the limits as you gain experience and confidence!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

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