"IF" the odor is indeed strongest near that pipe AND it run's straight outside through that wall. I would have someone who UNDERSTAND'S weather flashing inspect point where pipe enters siding (whether it is brick,Hardie Plank,vinyl or what). Water could be entering around pipe and ponding inside wall. The fact you report odor.is strongest near pipe and absent in other rooms tell's me you and the people you hire aren't going at this systematicly. For example Hvac Dirty Sock is in no from or fashion indicated which mean's you all are grasping at straws instead of troubleshooting.

Wow.

I know it may not seem systematic, but I've had my good friend who is a custom home builder out to the house 3 times. Like me, he's been unable to find anything with visual inspections of everything inside, outside, and in the attic.

The mold remediation guy came on a day when the smell was strong and smelled it too, but there ended up being no mold detected even though he felt 'confident' there was a leak in the wall.

The HVAC guy was a suggestion by the builder of this home. Even though the home was built 7 years ago, we remain friends and in touch so I reached out to him. He suggested the "dirty sock syndrome" even though I struggled with that explanation given the limited nature of the smell and it doesn't seem to emanate from any vents or HVAC equipment.

I'm attaching pics of the gas line where it enters the house. I don't see any obvious issues but I'm not an expert. Do you have suggestions on who to call next? A plumber? Home inspector?

Before doing anything about the pipe or other remedial work,have someone with a high quility thermal imaging camera take a few pictures of suspect areas. Tell them what you are looking for and they might suggest taking pics following rain. An area with higher moisture than surrounding will be cooler and show up in thermal scan. Energy audit services are one place that has thermal imaging equipment. Once pipe has been confirmed or eliminated as source of water intrusion,there's room for improvment.

Has anyone checked your vent pipes to make sure nothing is blocked? Is there a bathroom that you don't use that is causing a dried p pipe? That would be more of a sewer smell but a stink is a stink. Likely the path to resolution is what klem1 is advising but those are two easy things you can check.

One more thought. My parents had a moldy smell that turned out to be a dead mouse in the wall. My half beagle found it immediately when we came to visit.

@tozmo1 -- haven't checked the plumbing vents yet, but something I've considered. It just doesn't smell like a plumbing/sewer type thing but probably worth a look.

The rodent explanation is one we've also considered but the smell has probably been around a couple months now and it doesn't smell like dead rodent to me. Unfortunately I've gotten familiar with that smell at my work a few times.

Thermal imaging seems like it may be the next step... thanks all.

🤣🤣🤣 Definitely the front half! His back half was cocker spaniel but he had a tail as long as he was with long fur. He was quite a character.

Have you tested the humidity level in that particular room?

Cute doggy, both halves. :-D

Hi Steve! Were you ever able to determine the souce of your mildew smell? If so, What additional actions did you take to determine it? We are having the same issue in our house and i want to get it solved!! You can email me at:

sonya.mcafee@gmail.com

Thanks,

Sonya

Hi, Sonya. I spent a good bit of time on the outside of the home caulking around all entry points, including things like the gas line, the cable TV line, etc. And while we had the wall open, I used some expanding foam to seal around those entry points from the inside. That had been suggested by a home inspector/moisture remediation person that we had out to the house. We live in a wet climate (more than 60 inches of rain per year), and the inspector felt that at times when we were getting a lot of rain, some moisture was entering through those points and probably causing the smell. We have since moved from that house but haven't heard of any issues from the new homeowner, who we still see periodically.

Thanks for responding Steve! We have some irrigation drip lines that run to landscaling along the back side of our home where this smell is predominately noticed. We turned our Rainbird on about a month ago and now i am smelling this same mildewy odor as last year at this time. My husband checked our crawlspace last year but didnt find anything obvious. Guess we need to do some more investigating. We do have a natural gas line that comes into the house in this area as well, maybe the dripline water is entering along that and pooling? Hopefully we get it figured out. Thanks Steve!