Thermal Imaging Camera Selection for Home Inspectors

What thermal imaging camera should I buy as a home inspector?
This is a common question asked by home inspectors looking to get into infrared thermal imaging services in their home inspections.
There are many thermal cameras available on the market and all of them are not intended do all of the applications that we frequently use with thermal imaging.


The following request for assistance comes from a home inspector utilizing a Flir I7 thermal imaging camera.


Inspected a single level house yesterday and found moisture in the ceiling about 8 feet in from the front wall.  The moisture was about 4 feet in diameter. Saw it on my thermal camera and the paint was flaking.  Also moisture meter buried the needle at that location, but other areas of the ceiling the needle didn't move.  Went to the roof and all looked good.  Attic; no moisture staining, leaking and the insulation looked fine.  No pipes running through there as all the plumping is on the back of the house.  Here are the pictures (thermal, roof and attic).  Any thoughts?




I'll start by pointing out that this inspector may not have found this issue at all if it hadn't been for utilizing his thermal imaging camera. There is a possibility that peeling paint and his electronic moisture meter wood and identified a problem, but the thermal image documents the extent and potential cause for the elevated moisture.
We'll have to agree that the thermal scan is a very low contrast scan that doesn't really show us much more than the location and extent of the anomaly.
Unlike digital cameras that document reflected light, thermal imaging cameras collect information of energy radiating from objects in our environment. The amount of radiation is based upon the the objects temperature and its ability to absorb and radiate energy. When the radiating energy of the objects in the field of view of the thermal camera, the screen is blank. It takes a specified amount of temperature/energy differential to show up in the thermal scan and the camera's ability (sensitivity) will determine just how well the thermal analysis will progress.
So this inspector identified and documented a moisture condition and verified it with a backup test instrument (the moisture meter). What happens now? He will likely recommend further evaluation by the property owner and repair whatever they find.
The problem is, we have an issue (elevated moisture in the ceiling). But what is the problem? Where does this moisture come from? What is the actual defect? And how do we repair it?
This brings us to another subject; thermography training.
Thermography training is given in accordance with ASTM industry standards. But there is no requirement for this training and simple camera ownership is all that is necessary to perform thermal imaging during a home inspection.
"Thermography Certification" is commonly touted by thermal camera owners, but the reality is they are not likely to be certified. Only level III thermographers can be certified (but not all level III thermographers are certified).
The evidence is in the pudding as they say.
A thermogram is not a snapshot taken with a digital camera, it must be tuned and manipulated to identify the "target" (the reason why the scan was taken in the first place). Like we adjust our televisions for brightness and contrast, the thermal scan must be adjusted to be evaluated.
Thermal cameras are not thermometers. The temperature measurement displayed in the thermogram must be adjusted for the material being photographed and effects of the surrounding environmental conditions. If these corrections are not made, the temperature measurement should be removed from the thermogram.
Accurate temperature measurements are necessary, though some building science thermography trainers claim that these are qualitative and not quantitative scans. It just means they're too lazy to make the adjustment.
The temperature measurement is an important part of the documentation process because it could differentiate between a moisture anomaly and another type of anomaly such as cool air leakage. Without knowing the actual target temperature and the dewpoint temperature of the environment a vital bit of information is neglected.
Some say backing up their assessment using a moisture meter negates the need for thermal tuning. Well let's consider this, if we are in a climate zone with high humidity in the summertime and outdoor air is leaking through the building envelope and comes in contact with the air conditioning system (which operates below the dewpoint temperature of most summertime outdoor air conditions) condensation will form. The issue is a water leak, but the problem is not a roof leak but an air leak into the building! We are no closer in determining the the source of water by using a moisture meter with the thermal camera.
The following is the original thermal scan that has been tuned and adjusted, utilizing isotherms and appropriate palette selection.
Though there is considerable pixelization and poor spatial resolution we can see a pattern emerging. The coldest spots in the scan are directly above the window in the side wall. This area is now connected to the identified high moisture location indicated by the intermediate temperature color.
If you turn on your imagination you can begin to visualize what is happening.
If we verify our hypothesis through visual inspection (digital pictures) the lack of missing insulation, water stains on the roof framing, the lack of ventilator fan termination, plumbing supply lines, sanitary drain lines etc. we can "eliminate" many of the possibilities and then will be able to direct our "further evaluation" to assessing potential air leakage as the source of elevated moisture.
This is not the end of the story however. Though home inspection is usually a test drive of the building, reporting observations, making recommendations and then leaving the inspection report as the end game, adding thermography to the home inspection requires meeting the expectations of the service.
Home inspections are conducted to industry standards, but when a home inspector engages in thermography as part of that inspection the industry standards no longer apply.