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RESNET Thermography Guidelines

For the past several years, a dedicated group of thermographers has worked hard to develop and establish the new RESNET Guidelines for Thermographic Inspections of Buildings. I am thrilled to say it is now in place and ready to be applied! The entire RESNET Guidelines document can be viewed here.

The poorly installed blown-in cellulose becomes quite obvious when seen with a thermal imager that is operated by a qualified thermographer under the right conditions!

The RESNET Guidelines address the needs of building specialists who want to use thermal imaging as part of the RESNET audit and quality control processes. These guidelines establish a procedure for inspecting homes and small commercial frame buildings, as well as the criteria for which imagers can be used and the certification requirements of the thermographer.

Because there are many imagers in the market today that are not well-suited to use in building diagnostics, establishing minimum specifications for equipment was deemed critical. Thermal sensitivity is specified at 100mK or better, while spatial resolution is defined by the minimum array size (120×120 or better) and a suggested field of view (FOV) of approximately 20 degrees. The thermographer must also be able to adjust the span and level within either their infrared imager or their software. While “fixed-focus” systems are technically allowed, the onus is placed on the thermographer to ensure the images are in adequate focus; if not, another system must be utilized.

With a blower door in place and depressurizing the home, the thermal image clearly shows the infiltration of cold air into the wall cavity insulated with fiberglass batts.

The basic minimum conditions for both insulation and air leakage inspections are also specified. Insulation inspections can be either qualitative or quantitative, with the latter being accepted as an alternative to visual grading of insulation.

Conductions inspections require a minimum 18oF (10oC) of stable, delta

temperature (inside to outside). While work can be done with less, again the burden is on the thermographer to prove conditions are adequate—and the Guidelines help to address working with solar loading, wind and damp surfaces.

Air leakage work is done with at least a 3oF (1.7oC) delta temperature and must be done using a blower door operating at approximately 20 Pascals, with depressurization strongly suggested. When both inspections are being performed, the insulation work must be done first in order to reduce the chances of skewed results due to air movement.

Thermography, when used correctly, makes a huge difference in how buildings perform—and that is the reason the RESNET Guidelines were created by the author and others in the industry.

These Guidelines are an important step forward for all thermographers, but especially those RATERS who are using the technology under the auspices of the RESNET Mortgage Industry National Home Energy Rating System Standards. What happens there will have an undeniable impact on the rest of work being done by building thermographers—an exciting prospect!

Next week I’ll talk about the RESNET certification process that is

detailed in the Guidelines. I’d also like to put in a plug for the RESNET conference coming up in Orlando, FL February 28 – March 2. My colleague, Matt Schwoegler and I will be making several presentations and Fluke will be exhibiting. This conference is a great place to learn all about buildings and how thermography is being used in those particular settings.

Thinking Thermally,

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

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