By William Decker, CMI

As new technologies are developed, they become available in areas of use far from what they were originally developed for.  Thermal Imaging, also known as infrared imaging, is one such technology.  Originally developed during the Vietnam War to find enemy soldiers at night, it progressed to medical imaging, industrial testing and, finally, to the construction trades and building consultation.  Home inspections are a visual inspection, we can only report on what they can see.  Thermal imaging gives a professional home inspector the ability to see beyond the normally visible.

Make sure that when you hire a home inspector, who also does thermal imaging, that you hire one who has also been properly trained in how to use the imager.  Of the home inspectors in the Chicagoland area, less than 5% have any professional training.   Many inspectors buy an infrared camera, but never take the training courses or become properly certified.  Recognized American Standards for Non-Invasive Training certifications include Level 1, Level 2, Level 3 and Building Science courses, testing, continuing education and certification. Our inspectors are completely trained and certified, and have also presented professional papers at national Thermographer’s conferences.

First, let’s clear away some common myths about thermal imaging:

  • Thermal imaging DOES NOT see through walls.  The camera is very sensitive and can distinguish very minor differences in surface temperatures, id cannot look through solid material.  Forget about the things you have seen in spy movies.
  • Thermal imaging sees differences in temperature.  If an area appears to be cold, that DOES NOT automatically mean that the area has water.  It can me excessive moisture, but it can also just be cold.  That is why it is so important for the thermographer to be fully trained and to check out suspicious areas with other tools, such as a deep probing moisture meter.
  • Training is very important.  Anyone with $250 can purchase a cheap clip on thermal imager for their cell phone.  While these toys are cool, they are not professional grade equipment and are not being used by a trained and experienced thermographer.  False positives are just as damaging as missing a real problem.


It is the newest tool in the Home Inspection profession.  Read a recent Chicago Sun-Times article on the value of Thermal Imaging in home inspections.  Please note, while this is a good article, it is also misleading.  It presents thermal imaging as being like an x-ray, which can see through walls.  Newspaper reporters do not always get it correct.


Leaking washing machine leaking in wall, thermal image

A professional home inspector, equipped with a thermal imaging camera and properly trained and certified in its use, can find problems with a house that a normal home inspectors cannot.  These problems include:

  • Water intrusion through the houses exterior covering, whether the house has brick, stone, stucco or siding.
  • Improperly installed or settled insulation.
  • Water leaks around windows and doors.
  • Plumbing leaks inside the house, including leaking pipes, improperly seated toilets, leaky shower pans and bathtubs and water pipe condensation.
  • Improperly insulated HVAC ducting that have not been properly sealed or that cause condensation dripping in attics and crawlspaces.
  • Improperly installed or insufficient insulation in ceilings and walls.
  • Leaking roofs, skylights, roof vent piping and roof vents.


New house wth water intrusion problems

Water in a masonry wall, stone window sills not flashed.

These pictures show water intrusion into a single wythe CMU (Cinder Block) wall.  The builder did not properly flash the parapet wall coping or the stone window sills.  As a result, water had accumulated in the wall cavities (the purple areas under the window sill).  The spaces within the block were completely waterlogged.  Not only were the sills not flashed, allowing water to enter the wall through the window sills, they were also the same depth as the block and had no overhang or drip edges.

This was a $1.8 mil new construction house!

The client was VERY happy they had a thermal imaging home inspection.


House with no kick-out flashing at gutters

Water intrusion behind siding from gutter over-splash

This house had problems with the installation of the siding which has lead to water (purple area in the center of picture, right) infiltration behind the siding. The gutter / sidewall area was not equipped with kick-out flashing, so the gutter over-splash had entered behind the siding.

Thermal imaging is very good at finding these kind of problems with EIFS (Exterior Insulation Finishing System, also called Dry-Vit) and even masonry call coverings, but it should only be done by a qualified, trained and a properly trained and certified thermographer.


Here we see increased water in a wall and in the ceiling / roof trusses.  Note how the trusses are colder the closer they are to the exterior wall.

When the ceiling was opened, it was revealed that the entire roof truss system was water logged and rotted.  It was a good thing that this was found BEFORE the whole roof collapsed.

Water intrusion into ceiling.  Bad roof flashing

Water intrusion into ceiling, thermal image

Here we see another example of water intrusion, this time from badly installed siding and flashing on the house’s exterior, but seen from the inside of the house using thermal imaging during a home inspection.  Water intrusion is not always easy to diagnose, especially because a home inspection is supposed to be non-invasive.  Because water travels in so may ways (dripping, wicking, running, evaporation, condensation, etc) it is not easy to find the source.

Water intrusion is a common problem, and the source cannot, usually, be found without thermal imaging and an experienced, professional inspector.

High efficiency furnace, thermal image of operation

This is an interesting picture, even pretty.  It shows the operation of a 2004 Carrier category 4 high efficiency furnace draft blower.  Note the exhaust air vent on the lower right and the heated blower area.  Thermography is also used to check on the operation of industrial machinery, to determine if there are worn out motors, gears or bearings and even, using analysis software, calculate the operation efficiency of the furnace.  This type of preventative maintenance inspection is used to predict equipment failure and avoid the problem of down time while the equipment is being repaired.

High efficiency furnaces should have both combustion intake air and combustion exhaust vents in order to achieve their designed energy efficiency.  Most inexperienced builders (all too common for new construction) do not know this and you may be using more energy than you need to, and paying for it.  This condition is usually easily and inexpensively repairable.

Your house may be insulated, but that does not mean it is properly insulated.  Many times, the insulation contractors are not professional and don’t know how to properly install the insulation.

Thermal imaging can not only find areas of improper insulation but also water and moisture intrusion areas as well as places where cold air is blowing through the insulation and through electrical receptacle boxes.

Cold air leakage because of badly installed insulation

The image above shows wet and settling blown-in cellulose insulation.  This commonly happens with this type of insulation after a few years.

The image on the right image shows an area of cold air infiltration into the house through an electrical outlet.  Current energy codes call for all such openings to be sealed against cold air infiltration, but in this case the problem was having the insulation installed by a non-professional installer.

Rates in a crawlspace, thermal image

Thermal imaging can also be used to detect uninvited guests living in your house.  This picture shows two rats that had taken up residence in the crawlspace of the house.  Raccoons and squirrels in attics, as well as termites and carpenter ants in the house’s beams and walls can also be detected.

Termite infestations generally appear as “hot” areas because of all the body heat that termites produce.  Carpenter ants, unlike termites, do not actually eat the wood, but burrow in older, soft wood to make their nests.


Thermal image of wall, no insulation, with studs cooler

This picture shows, from the inside, an exterior wall of a newer house.  The exterior is covered with cement fiber siding.  There is only a 3 degree variation in temperature between the drywall covering over the wooden studs (the blue vertical lines) and the drywall covering the insulated stud bay area.  Such differences are perfectly normal.

A common public misconception is that thermal imaging can “see through walls”.  Images like these seem to perpetuate that belief.  Remember, it is not enough for the home inspector to use a thermal imaging camera, they also need the necessary training to be able to properly interpret the image.  Incorrect interpretation can mean missing problems in the house as well as calling out defects that are not actually there.


Barrel ceiling with radient water heating

Barrel ceiling with radiant heating, thermal image

These images show radiant heating pipes in the ceiling of a house heated by a hot water boiler.  Water is heated and circulated through copper piping and the heat radiates downward.  The piping can be installed in the floors of the whole house, in bathrooms and in basements.

A home inspection that includes thermal imaging is can find leaks in this piping and find the problem while is is still small and easily repaired.


Overheated circuit breaker in panel, thermal image

This image shows an electrical panel.  The breaker in the lower right was rated for 15 amps, but the circuit was serving a newly installed furnace blower motor that was rated for 20 amps of load.  Undetected, this problem could have caused serious damage.  A good home inspector would probably have found this problem, but thermal imaging can find it quicker

Thermal Imaging can detect loose electrical connection in the house’s electrical system, bad switches and outlets and overheated wiring.  Electrical defects are a common cause of house fires and are often the result of older wiring deteriorating or new electrical work that was not done properly.

Thermal imaging can give the homeowner assurance that the house’s electrical system is safe, not overloaded and has been properly maintained.

Thermal imaging in home inspection has many uses:

  • Finding water leaks, water and air infiltration in walls, ceilings, through masonry, floors, above windows and doors.
  • Evaluation of the electrical system of the house, looking for ‘hot’ connections and aging, overheating circuit beakers.
  • Wood destroying insect infestation.
  • Insulation efficiency and coverage.
  • Energy efficiency and use evaluation, energy audits, HVAC duct leakage.
  • Aged electrical receptacles, circuit breakers, loose wiring connections.
  • Possible areas of mold buildup.
  • Roof leakage