Vacant house, for some time. Walk through and offer a week or so before our inspection. Lingering smell in the house then. Lingering smell as we walked in the door. Standing in the entry everyone turned to me to ask, "What's that smell?" Well, the smell was moisture, and it was established!
"Let's look around the outside first." Usually I am at a house earlier than the buyers and have walked around the house a couple of times. In this instance, they were very early and I hadn't had my usual shot at that! I love it when the buyers are early, by the way.
What did we see? Tall trees and fallen limbs.
TREE LIMBS DON'T LOOK HEAVY. THEY ARE. WHEN THEY FALL ON HOUSES THEY CAN DO DAMAGE.
These limbs weren't huge. One larger one was beside the corner of the house, and there was evident damage above to the gutter and lower end of the roof. There were shingles damaged at the peak of the roof, clearly visible, but no limbs residing. One must have hit and fallen off or was blown off by wind.
This is how the thermal camera saw the peak of the cathedral ceiling at the top of the roof.
NO STAINS WERE VISIBLE ON THE DRYWALL. So this problem would have been invisible without the camera.
Interestingly, the left image is the front of the house, in the sun. The right image is the rear, more oblique to the sun, but also shaded. White, yellow and orange indicate warmer colors in this palette.
You can clearly see how warm the ceiling and wall are in the left image, at least by comparison to the right image!
And the cooler colors, as demonstrated by the dark purple and blues, are more pronounced in the left as they show a starker contrast. This is very instructive. Shade on the outside of a house can throw you off if you don't pay attention!
Those cooler colors clearly indicate moisture. There is no other reason for cooler colors on a day in the 90s. Why would that moisture smell? Think carefully!
And what of the lower end of the roof near the damaged gutter?
This is what the corner of the bedroom looks like behind that damaged gutter. Flat ceiling, 90 degree wall, and again, moisture evident. This is also a shaded area, on the other end of the house. Notice how the first stud in the wall has diverted the moisture lower down, where it has migrated a bit across the wall via insulation.
So, remember the formula: broken limbs + damaged shingles = moisture. But all the time? Maybe not. IT WORKS IN THIS CASE THOUGH!
Why the smell? While not visible on the interior of the drywall yet, there is probable fungal growth in there as this problem has had time to develop and given "conducive conditions" (i.e. moisture) fungi and molds can take root rapidly!
This is an easy thing to refer to a roofer for repairs and a mold remediation company for assessment and eradication. My job is done!
My recommendation: thermal imaging is useful, instructive and the images are definitive. Extremely sensitive to temperature differences, these cameras can demonstrate exactly where such differences are. Moisture presence, falling insulation, electrical anomalies, leaking duct work, animals inside the wall - anything that can produce temperature changes can be detected by the camera. It is fabulous technology.
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
Good morning, Jay. You make some good arguments here. Most of the moisture related odors I find generally come from the crawl...
Very Interesting- I have attended Home Inspection where the Inspector used this technology and it is remarkable- it can detect what the human eye cannot see.
I have to EDUCATE rental property owners on trees * Limbs and Roots. I just had sycamore tree limbs "lifted" fron the roof of a rental home...home will get MORE light and roof will get LESS damage!
Love the thermal images as those pretty much call it what it is! While I am sure the sellers won't be too happy, you are doing your job. It's very hard to price "smell" until the quotes start coming in to rectify the situation.
Michael - sure, but when they are on the upper level that is a watch-out moment!
Exactly St. Cloud. You are looking at about 307,200 separate temperature points in each of those images, assembled together by the camera.
Wallace - trees and limbs are a frequent topic of conversation during home inspections!
Barb - what the seller thinks is irrelevant. And this could have happened after they moved out!
Jay, Love how the camera sees all, tells all! Great tool to have in the arsenal :)
Jay: How much training is involved to use the camera? And is the price coming down? We are starting to see more cameras - not sure how many inspectors are really trained though.
Just spoke with an agent yesterday and we talked about smells that refused to disappear and she told ne about the house she almost didn't sell...a mouse died in the wall...ewww ewww ewww...
Jay - love thermal imaging!
That camera sure comes in handy. I bet this sort of stuff can happen more easily when no one is living there and paying attention to smells.
Technology has taken us to new heights! What in the world did we do without all these wonderful tools. This is so helpful and informative. Hope you had a grand Father's Day!
Great detective work Jay. I was fascinated at how well your experience and tools led you to the root of the problem.
Good morning Jay. Thermal imaging while doing an inpsections looks like the only way to go. Nice catch.
Good morning Jay. Class never ends, thanks again for a very good lesson.
Very informative Jay! Your thermal imaging says it all. Thanks for the post.
You are right about the thermal images never being wrong. Excellent tool to have to solve water damage and dry rot issues.
Thanks Jay.
Your home need an X-Ray call Jay
Hire a professional that not only is a pro but up to date on all the technology
Enjoy the day
Moisture in the walls and attic is always a good thing, if you live in the ocean. But not here. Glad you have that camera and are trained to use it!
Love my IR camera. The things I find.
Here I thought you were going to say the smell perhaps came from somewhere else. I have on occasion heard that very same phrase at home.
What an interesting post... I would never have thought to use thermal imaging... huh...
Jay - what kind of thermal imaging camera do you use? Do you charge extra if the buyer wants this service or is it a part of your basic package?
Bliz - so long as the images are interpreted correctly!
Anne - yes, training is essential! It is time consuming and expensive, but also important that it be coupled with practice and more practice. It is easy to misinterpret results. My camera is a little more than 50% cheaper now than it was when I bought it. It is available now for about $8K.
S&D - a single mouse in the wall would not produce that much odor!
Carol - I do too! It is fun to use, and people are really impressed!
Debbie - I don't know how long the house was vacant or when these problems began, but the recent weather could have magnified the odors.
Tish - and yet a very small percentage of home inspectors actually have and use the device.
Thanks Gabe. You have to look at everything and put together what is tied together!
Randy - the mental paradigm shift has not occurred yet to where consumers are demanding this service! I would love to do more exams! The extra cost is minimal.
You are welcome again Ken! Class starts most every day. Attendance is mandatory.
You're welcome Juan. It is a definitive report when all is said and done.
The image is definitive Tom, but sometimes the interpretation is lacking. It is both art and science.
http://activerain.com/blogsview/1921798/thermal-imaging-is-sometimes-science-and-sometimes-art
Thanks Don. I am glad more inspectors here don't have the device! I get the job!
I am glad I have it too Jeremy! It makes me a lot of money.
Jim - like an open sewer clean out? I usually tease female purchasers that they should stand beside the plumber when he pulls the cover off the clean out so they get the full benefit of the experience!
Chris - different strokes for different folks!
I use the SPI RAZ-IR camera Cynthia. Even at 8 years old it is still a very good device.
http://www.x20.org/raz-ir-pro-thermal-camera
Jay, you know that this is one... toy, er, I mean "tool" that I must have ;-)
Jay,
It can be hard to figure if that musty smell is there to stay or if they need to air the place out and run the bath fans.
Jay,
Good catch. Really pays to have the right equipment and the knowledge to use them right.
Well, look around Chris! And don't get a cheap one. You will find in time that it wasn't worth it.
Mason - it got more pronounced as we got upstairs and into those rooms. Hard to tell if the AC or fans will control it. I think there is something inside the walls, but that isn't my purview to figure out! You are in an area where these cameras would come in handy. Your grand dad might be too old a dog for this new trick, but as you are starting out you should consider getting one and some training!
Don - every time I want a "new" tool, or toy as my wife calls it, my wife complains, until she sees that it was a valuable thing to buy!