It appears that you have multiple issues going on which may or may not be related to one another. There is obviously something going on the requires a formal inspection of the siding.
I can see apparent moisture patterns occurring at the eve, below the HVAC flue pipes and at the foundation or the siding is below grade.
Still, there are a lot of things that are geometrical.
There is a probability that moisture has infiltrated the wall at the eve causing excessive moisture in the stud bays which has deteriorated. The deterioration may be excessive in the corner in the installation as well as framing allowing hot air to flow throughout the affected stud bays giving us the geometrical look.
You can see where the interior floor is, both visual and thermal. There is no reason for the moisture to stop here if it is on the backside of the siding.
The area where the siding is below grade, appears to be wicking moisture from the soil. However the concrete foundation is also saturated beyond that of the siding. There may be more complicated issues here as well.
The HVAC flue pipe wall penetration appears to be leaking from the exterior penetration. [size=2]High-efficiency furnace flues have a slope back towards the furnace. If the exterior flue pipe is still sloping upwards, surface water tension will cause it to flow back to the pipe penetration and possibly infiltrate the wall if not properly sealed. [size=2]This could also just be air leakage from the interior. The moisture stain may just be from the upsloped flue pipe.
[/size]
You should be able to see the framed wall from the crawlspace/basement, no? What did you see here?
The thermal pattern below the eave (which appears to be moisture) does not connect at the junction of the eve/siding. This area should have the greatest amount of thermal capacitance due to moisture.
The situation we are observing may be a condition in transformation. A leaking interior wall may be drying the moisture anomaly which may have occurred sometime ago. [size=2]Further thermal testing is required.
You ask about what other information is needed, detailed weather records as far back as the last substantial precipitation occurrence is necessary. It is not always necessary just to know the temperature and humidity at the time of inspection, but the weather pattern that occurred prior to as well. I cut and paste the database from the National Weather Service into my report files.
Orientation of the building is critical.
Were you unable to get any thermal scans from the interior? If there is moisture damage in there we should be seeing something.
[size=2]I think this situation requires a follow-up inspection under different conditions (or controlled timing under the right conditions). This is what infrared inspections is about.
You have no baseline. You have nothing to compare this with. Everything is just “apparent”.
Does this condition warrant further expenditure of funds on the part of your client? Due to the size of the anomaly I would say yes.
[/size][/size][/size]