Is it mould growth?
While mould growth on the ceiling is often obvious, there is another building defect that can look very similar. It’s called ghosting. It occurs when soot and dust particles stick to the ceiling. Over time, these particles cause a permanent stain. The clue is in the pattern. Ghosting often appears in perfectly straight lines.
The lines correspond to the framing joists in the attic above. The framing is a worse insulator than the surrounding attic insulation, which passes through to the ceiling below (thermal bridging). The colder temperature in the attic space leads to condensation in the rooms below with higher humidity, which causes the soot and dust particles to stick. This can be mould growth. We can always do mold testing if need be, but if it's just a small amount the health impacts are very small and can be removed by the home owner.
Symptoms of humidity based Ghosting:
- Ghosting is worse at the perimeter of the room
- The room is on the top floor or has an attic space above it
- The attic is poorly insulated
- High humidity due to lack of ventilation
So how to do you fix the issue?
Well there are some easy fixes for this.
- Adding more insulation to the attic space will help keep the framing system warmer and reduce condensation Plus......... reduce your heating and cooling costs. Win Win!
- Reduce the humidity in your home by using exhaust fans or look at adding an HRV (Heat Recovery Ventilator) system.
- Add humidistat controls to automatically turn on exhaust fans as the humidity rises due to showering etc.
- Another trick that we have used in our home was to turn the furnace fan to the "on" position, this is constantly moving the air throughout the home. (Heating season)
These stains can be difficult to remove without damaging a textured non painted ceiling. It's most likely best to paint the ceiling and follow the recommendations above.
Painted ceiling, scrub away or re-paint.
Hope this helps.......and please share this on your page.
Rick Clayton IICRC certified.