Possible causes
- Roof leak
- Bathroom fan venting into attic
- Poor attic ventilation
- Condensation
- Wet insulation
Useful photos
- Sheathing discoloration
- Roof penetration areas
- Bathroom fan ducting
- Insulation moisture
- Ventilation path
Safety notes
- Avoid unsafe attic access
- Do not disturb insulation or growth
- Watch for electrical hazards
- Use a qualified provider for hard-to-access areas