IR anomaly; moisture or insulation issue?

Looking for some input on these vaulted ceiling images: This is from an energy audit and the images were made under natural conditions, prior to house depressurization. Outside temperature was 35 and inside was 66. The sun was starting to shine on the roof image area, it was morning about 9am on a sunny day.

How to tell if these anomolies are insulation voids or moisture? I didn’t think to check with a moisture meter at the time. The house had visible vapor barrier issues viewed in the attic (poly, not taped, quite leaky house from blower door test, ice dam issues in another roof area). This area is drywall, both wall and ceiling, which does act as an air and somewhat a moisture barrier. Fiberglass batt insulation, which was reasonably well installed but not perfect. I’m thinking moisture. Is there a way to identify moisture from an IR image only?

Is the only way to confirm moisture vs insulation void is follow up with a moisture meter?

The owner said she had leakage issues through the top of the wall installed windows below the areas of the first 2 images. The second two images are an adjacent room, same area where the roof meets the ceiling. The last two images are higher up on the roof plain.

I did not go up on the roof. This was not a full home inspection, although if I was astute enough to have checked the ceiling with a moisture meter, I surely would have taken a look at the shingles. Shoulda-woulda-coulda…

IR005203 IR005204 IR005208 IR005208 IR005211 IR005212

The mottled areas of the pictures are, typically, indicative of missing or misplaced insulation.


Thanks for your reply. Observations of curiosity: the rafters are generally showing up as warm, as are areas of insulation. Sun recently started radiating on the roof. Then the cooler areas; is this moist insulation warming up at a slower rate than the rafters and the dry insulation?

The wall top areas do not show this temperature change, which is curious. The gable end was facing the sun but maybe shaded by trees and the eave was still shaded. The wall framing members show up as cooler than the insulation areas, which makes sense on the eaves but maybe yes or no on the gable end.

I do have to return to the property for a follow up meeting and will use my moisture meter.

Very narrow range in temperature differential between warm and cool areas. That’s the proverbial can of worms using IR to ID moisture, you can really only validate it with a moisture meter. I think what you are seeing is variation in the insulation installation. Area along the rake in 3rd and 4th picture would be suspect for water intrusion, but there is no indication on adjacent wall which would vulnerable to leak at roof’s edge. I think it’s just variation in insulation.

Looking at the IR images without taking into consideration the environment and the structure does not give a total picture of what might be occurring at this structure.
If we indicate moisture without verifying it with a moisture meter we may be in error. The IR image does appear to support an indication of moisture but it may also be variations in the insulation or ventilation of the roof system.
To be sure of what it truly occurring I would want to check several areas with my moisture meter and definitely take a good look at the roof covering to make sure it is properly installed and functional.

First of all you should not be doing these types of inspections if your not trained and do not follow IR Protocol.

This is obviously air leakage. If you use a moisture meter it may pick up moisture. But when warm air meets cold air condensation forms. So would you think this is a water leak, or air leak bases on the moisture meter? Chicken or the egg?

If you knew how to run your camera and determine corrected temperature, and how to determine wet bulb temperature with your camera, you could tell if it was wet or not without a moisture meter.

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Unlike your listed certifications, I’m only a level 1 Snell Group certified thermographer. I’m also a BPI certified Building Analyst.

During my Snell Group class about 4 years ago, we were never taught how to determine wet bulb temperature with the IR imager. Is that a level 2 or 3 skill set? I’m all ears to furthering my knowledge, which is why I made my initial post. It appears you have that knowledge.

In order to detect moisture in insulation, my training says you have to have a dynamic condition. In this case, the sun warming the cold roof. My concern was this anomaly was accumulated moisture in the fiberglass insulation due to condensation of indoor air that leaked through the poorly sealed vapor retarder. That condition may easily exist in this roof, with the way the building was built. It now is the end of a cold winter. I’m located in far northern Minnesota.

I doubt very much that it’s roof leakage, although an inspection of the shingles and roof area would be a prudent follow up. The home has a history of ice dams, although, as I was told, not at this location.

I was hoping this could be an educational discussion, not a slam. I assumed the purpose of these forums was informational and educational. I’m so disappointed!


Great words, I read most of these forum topics to learn new and forgotten things, I like seeing and understanding regional specific builds because it may show up in my area as people do move around and there are lots of backyard handyman hacks that are creative and I whole hardheadedly believe in peer review. Let’s keep it positive and share with us your wisdom.

In light of your training, this becomes more concerning to me. I learned these things before I ever took Level I (during Building Science Class) and it was also discussed in BPI training. As a matter of fact, BPI stole a scan of mine from my web site which was used as a moisture/air leakage example in class. I asked where they took the scan and they said they ‘took it’. Yup, they took it right off my web site!

As for determining moisture in an IR scan, I have discussed this here several times. As a matter of fact, I passed on information I developed for a Flir convention clinic I presented that has never been taught anywhere else. Without going into the nitty gritty again, there are obvious things that you can do on site without all kinds of equipment and testing, rather just your IR Camera that you can utilize.

First; you must fully understand the three methods of heat transfer. And that these three methods must add up to 100%. When you understand conduction, convection and radiation you can better understand what is presented in your thermal scans.

Second; you must know what your looking for first and adjust your camera for this. When you see a big blue spot, the first thing you think of should not be water. It is just a temperature differential of things in view of your camera. SO speaking of temperature differential, you must properly tune your camera or the differential will not be even close to correct. In your example (assuming your camera was properly set) you have an apparent temperature differential of 20 degrees F. Is it possible for moisture to be 20 degrees below ambient of the indoor air? No, not likely. This is where wet bulb comes in to play. Again, without any more testing tools (moisture meters, hygrometer, psychrometric charts) there is a simple method you can use. Have you ever noticed a bath towel, or kitchen wash cloth that was really cold from previous use? These are cold because of evaporative cooling (wet bulb). Without even adjusting your camera, what is the apparent temperature of these damp cloths? Then what is the apparent temperature of your blue spot? Is it close?

Third; following protocol. What is the protocol of BPI or Thermal Imaging when a Thermal Exception is located? You did not use a moisture meter, but your here to get answers without following protocol. Why? As I have discussed numerous times in the past, a moisture meter is not a definitive check for moisture any more than just the IR camera. As a matter of fact, if you follow the procedure above, the IR camera is a better moisture meter than a moisture meter.

Fourth; so what must you do once you get indications of moisture? Answer: Determine it’s source so it can be fixed. You can’t find moisture then tell your client to get someone else in there to ‘Further Evaluate and Repair’. They have tools to fix a problem, and you have diagnostic tools to locate and evaluate. You can’t play Home Inspector when your using the tools and certifications you exploit on your web site. That is why you get paid the big bucks! Your doing a Home Inspection as well as an Energy or Building Science Consultant and must follow the protocol of those sciences, not take shortcuts.

I have developed another procedure for positive identification of moisture that has been approved by Flir, who have paid me to teach it. Everything in life is not free. I’m sorry your disappointed that everything here isn’t free. I am also sorry that you feel this was a ‘slam’! Sometimes the truth hurts. You yourself said you didn’t bother to use a moisture meter. This is excepted by all as the next step you should have taken. You come here with incomplete information and expect not to be ‘slammed’? Based solely on this, “You should not be conducting these inspections”, stands.

Inspectors call me all the time for help in these matters and I fully support them when they take things to the next level in their search for greater competency. If you do your job, I’ll gladly help. But if your scamming your client with incompetency through laziness I’ll let you know about that as well.

Hope this helps some of you…

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With all due respect to everyone who responded to the original post, my experience with IR as a sole source of moisture detection has shown, IR is a diagnostic tool, but I would rely on it as last word.

Case in point. I recently looked at a home with client (I’m a licensed realtor). FWIW, client was my son. Very nice home, exterior was traditional hard coat stucco. Seller had IR scan of exterior done few months ago, indicating “0” problems in the seller’s disclosure. I have personally never seen “0” moisture penetration on any home, regardless of the siding installed, let alone stucco. We looked at the home, layout was nice, overall in excellent condition. I made a deal with the seller that I would do couple moisture test areas prior to submitting an offer, rather than after acceptance of the offer.Seller agreed. Tested four areas. Sure enough, reported areas indicated as no moisture, two of those were above 20%.
We used IR to diagnose pumps and equipment quite regularly in the company I had worked for. Those temperature differentials are far greater than 20*. Great diagnostic tool, but in my humble opinion, I wouldn’t bet the farm on just IR.

TI is a science, not a tool. It is only as good as the operator.

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Completely agree. Operator opinion and training plays a role. Practice of law always boils down to measurable facts. When in doubt, quote stats.

David, your first step in the overall assessment of a building was to become involved in ‘building sciences’ and furthered the assessment protocol with TI. I find, rightly or wrongly, to many inspectors miss/skip/gloss-over building sciences, which to me is one of the most important diagnostic tools in you home inspection assessment tool box.

As for wet/dry bulb remark in one of your posts. One can easily purchase a tool, Thermo-Hygrometer, to help them assist and develop a good assessment protocol. Add TI and you do/did yourself, as well as your clients, a favor.

Too bad John McKenna, Level II Thermographer, The TI instructor through InterNACI, never went deeper into building sciences with his Thermal Imaging classes/coursers.

I sure miss John. I bet many do. He was a true professional.
John McKenna, You were one of the good guys!

Looks like air…

You will not see rafters per say. Ceiling joists or truss lower chords.

Poorly distributed insulation. A look in the attic will verify findings.