Thermal Imagers are indeed a very useful tool but you really need to fully understand what the imager sees to understand what it can do, and more importantly what it can't do.  There are times and conditions under which the imager is blind, and there are also conditions which will "Fool" the imager into showing artifacts that are not really there.  Additionally, some things that look really really weird, are just fine. Again you need to know what the imager is seeing, and what you SHOULD be seeing.  Classroom theory is a nice thing, but Inspections by Bob believes that experience and an understanding of what is going on is more important for the home inspector to be able to "read" the images the thermal imager provides.

Yes, Inspections by Bob has a Thermal Imager, and we don't use it very much, but when we do use it, it provides a view that no other tool could.  Also please note that our STANDARD contract specifically states that we cannot address those items which we cannot SEE. A thermal imager allows us to see indicators of possible issues, but we still cannot see through walls. We can see symptoms that may be indicators of something inside the wall, but the only way to see inside the wall for sure is to cut a hole...and we don't do that.

Thermal Imagers see radiant Heat, and can measure the amount of heat that they are seeing ,very precisely... routinely to less than 1/10th of 1 degree Celsius.

How does this help the home buyer, as thermal imaging is not part of a normal inspection?  If I suspect a problem I may take out the imager to confirm something that I suspect, or that other indicators point to,  Recently in a newly constructed house the builder had to open up a wall to reconnect the heat pump refrigerant lines. The wall "felt" cold, as did the room. Lets start with what a "Normal" wall looks like.

You can see the wall studs, barely, but in the majority of the wall there is not much difference between the insulated section and the stud section.  Where two wall sections meet there is a bit more difference, but not a lot.  I would probably rate this as "Acceptable".

However, looking at the wall NEXT TO this one, we see something different.

Note: We started with a standard inspection, something was suspected, our standard observations (hands, eyes) lead us to believe there was a possible hidden issue. The thermal imager allowed us to "see" what we had felt with our hands.  We cannot SAY for certain what the issue is that is causing these images without cutting holes as we still can't see through walls.

Using a thermal imager is not practical on every inspection as it takes a lot of time to setup properly.  And if the outside is the same temperature as inside, the camera will be blind. (remember the empty foam cup?) I use the thermal imager as a tool, just like my outlet tester, moisture meter, thermometer, flammable gas detector and the myriad of other things in my car.

Remember where I said that at times Thermal Imaging is blind?  There actually is a standard that describes the procedure for inspecting insulation in Frame buildings (ASTM C 1060) and it says (in far too many words) that you really need a MINIMUM of 18°F difference between the interior and exterior, with a recomended interior temperature near 70.  That means that the EXTERIOR temperature really needs to be below 50 or above 80 for adequate images.  The ASTM standard also says that you can adjust the interior temperature as needed, but it must be STABLE and recomends a 3-HOUR pre-inspection conditioning period.