Sucking or Blowing Steven.
The attic should be static. load able to evacuate RH easily.
If it is soot from the attic it is blowing into the conditioned space. (The pics show a little issue.)
At a low rate by the particulate build-up.
Why?
Pour attic venting system ?
Negative pressure in the home?
WHY?
All homes breath to a certain degree. Inhale and exhale.
Mechanical conditioning, attic and wall venting and shear loading all play a roll.
Ghosting can be a common factor for homes.
Wall, ceiling opening; Lighting, sconces recessed can lighting fixtures , electrical outlets can tell you about the homes overall venting.
Questions I ask myself.
- What type of heating system? Forced air draft and ducting balanced?
The returns all open.
Chimney soot on the crown or cap speaks in volumes about over all balance… - The attic venting system correct. (how many are?)
- The exterior envelope sealed? I spend time on Windows. Caulk!!
- Fire place. How often do they use it.
- BURNING CHEEP CANDLES.