The bird-blocking at the soffits was at every other truss bay. The ghosting appears at the truss bays that were not ventilated. I have never seen this type of ghosting before. Anyone know what caused it?
Temperature inversion.
It draws crap in the air to the temperature differential which sticks to the ceiling.
There are more detailed explanations if you Google “ghosting”.
see it quite often with people that burn candles in the house.
Ghosting can happen when there is a difference in wall surface temperature between the stud and the wall cavity areas. A wall’s thermal characteristics, construction practices, and climatic conditions influence wall surface temperatures. The distribution or circulation of dust, dirt or soot from burning candles, running gas log fireplaces or forced air systems in the home will distribute particulate until they come into contact with the colder surface and produce the discoloration over time. Cleaning the surface and limiting the amount of soot or dust particulate in the home seems to be the key. Replace heating system filters regularly, limit the quantity of candles burning in the home will help reduce this phenomenon.
Additionally, some of the plug-in air fresheners are really bad.
Hey Paul
Did the insulation cover the entire ceiling all the way to the edge?
Just the way the ghosting appears is backwards from what I normally see.
What I see typically is the ghosting along trusses because they are the colder surface due to thermal bridging.
In your picture the ghosting occured between trusses, which means the ceiling was colder, making me wonder if there was adequate insulation installed in those areas. Granted there is only so much insulation that can be installed out to the edge of the attic, with the roof pitch.
BTW Candles are a huge contributor. After we repainted our interior, my wife agreed to not burn them, and we have not had any ghosting return, even after 4 years.