Dryer vents plumbing vents kitchen or bathroom fans vented into the attic.
Mold in attic above bathroom.
Paint the bathroom ceiling with a high sheen gloss paint.
Attics usually have a passive ventilation system in which outside air comes in through the soffit eave vents at the bottom warms up in the attic and escapes through the can or ridge vents at the top because hot air rises.
This is why you rarely find mold growth in the attic above a garage or a rarely used portion of the home.
The most common cause of attic mold by far is blocked or insufficient ventilation of the attic space.
Mold needs 3 things to grow.
As air leaks migrates from the home into the attic it carries soot and dust particles.
Related to 3 above this practice can pump warm moist air into the attic where it can be trapped and begin the cycle of mold growth.
Mold species such as stachybotrys chartarum which looks like slimy growth loves attic basement bathroom and space under the sink black mold can also grow behind the walls or attic ceilings completely undetected until the occupants smell the presence or experience health problems.
Insulate the attic space above the bathroom to prevent excessively cold surfaces on the ceiling.
If you eliminate just one of these elements mold will starve and die.
This is a different perspective from the other video about bathroom fan venting causing mold.
Moisture food and warmth.
Matte and other low sheen paints absorb much more moisture which in turn leads to mold growth.