I received a call from a couple who are experiencing track lines under each window of their home. This never happened until they had cellulose insulation blown in. Now they can see the outline of the wall studs. The property owner has already viewed the interior of one wall and has found a void. I am thinking this may be the case for all the others, and I will see it first hand this weekend. Any thoughts as to whether this is missing insulation or a possible moisture issue?
Humidity.
Where are you located?
How did the owner find a void?
It sounds like a case for a qualified infrared thermographer.
Perhaps ghosting due to thermal bridging at the studs.