All objects and surfaces in a building reflect, absorb and emit heat at different rates. Thermal Imagers (AKA Infrared cameras) can see the differences in the heat signatures of various objects and surfaces and put them into a colorful spectrum that we can make sense of. Color settings are varied but typically cold surfaces show up darker and hot surfaces appear to be brighter in thermal images.
During a home inspection, infrared imaging is a very useful tool that can highlight defects invisible to the naked eye. A wet surface such as window trim or sheetrock will be cooler than the surrounding materials and so it will show up as a different color (usually darker) through the lens of a thermal imager. This means roof, window and plumbing leaks can be detected in infrared even if there is no visible staining in the area.
Thermal imagers are also very good at finding insulation defects. In the hot summer an area of missing attic or wall insulation that allows heat to transfer into the living area from an attic space is easily visible during an interior infrared scan because the hot area glows bright yellow. During the winter a missing portion of insulation will be colder due to heat loss and will show up dark purple (in typical color settings.) Missing insulation is one of the most common defects noted via infrared inspection, and is usually one of the easiest home repairs with the most return on investment.
Some of the most serious defects noted via infrared inspection are electrical hot spots. Loose connections or faulty components at switches, outlets and breakers can increase electrical resistance which results in excessive heat. Overheated wires eventually become discolored and melted over time but visible cues are not always present. A loose lug nut on a main service cable feeding a load center can look perfectly fine during visual inspection but may be glowing through an infrared lens at a scorching 500° due to overheating–I’ve seen it!
The infrared camera is also a useful tool for testing heating and cooling performance. Thermograms with center spot temps show an accurate temperature, which provides quantitative evidence of system performance. Quantitative evidence (data and numbers) can help show adequate or poor performance, but the qualitative evidence (pretty colors and temperature differences) can show defects such as leaky ducts or poor air supply. It is surprisingly common in new construction to have a supply vent accidentally covered up by sheetrock. The brand new ceiling may look perfectly normal but the infrared image will show a rectangular hot or cold spot indicating the exact location of the supply air duct that was closed up.
As a Certified Level 1 Thermographer, I never leave the house without my thermal imager. Radiant Home Inspections always utilize infrared imaging and every report includes digital thermograms. There is no up-charge for this service–it’s included as a part of every RHI inspection because it helps us do a better job. If you’re not using thermal imaging you’re not getting the whole picture.