What Causes Black Spots on Insulation?

What Causes Black Spots on Insulation?

Experts suggest doing an annual home inspection for routine changes and maintenance because with Ontario’s continually changing weather, your home is at risk from a multitude of factors. With the higher humidity of Southern Ontario, like in Kitchener-Waterloo, Mississauga, or Hamilton, mould is a concern and you might need to consider having your insulation removed or replaced.

If you see blackspots on your attic insulation mould can’t be ruled out, but it is possible that there’s another cause. Air leakage from inside the house through the walls and ceilings can produce some pretty dramatic localized black spots in fiberglass batts.

Typically, fiberglass batting isn’t good at stopping air leakage, but it does act as a very effective filter material for airborne dust particles. Dirty insulation is a phenomenon that is especially common in older, leaky houses. Air leakage through electrical outlets, wiring penetrations, gaps in the vapor retarder, and gaps around furnace ducting, chimney can cause dark streaks to appear on your insulation.

Black Spots on Insulation caused by Air Leakage

Particulates released by combustion appliances, such as wood stoves, boilers, furnaces, diesel heaters or auto exhaust, can produce very fine soot that can build up over time in insulation. Tobacco smoke can also contribute. To determine if the problem is moisture and mould, or an air leakage pathway – have a closer look:

  • Does the wood framing or sheathing around the insulation also have black spots? If not, it is more indicative of dirt than mould.
  • Look for clues in the pattern of the dark stuff. Does it match up with an air leakage pathway from inside the home like an unsealed electrical penetration in the ceiling and follow the wiring through the insulation, depositing dirt in the surrounding fiberglass along the way.
  • If you are still concerned that you may have a mould problem, call a mould expert to make a positive identification. 

Minimizing Mould Damage to your Insulation

For an air leakage pathway, sealing the leak will end the problem, as save you on your energy expenditures. For mould, if you’re able to act quickly, you can minimize the damage:

  • Disconnect the power - unplug any electronics, and remove electronics, furniture and movable items immediately;
  • Get rid of the water - use old towels, buckets and mops to soak up as much water as possible. This may include bagging and removing the infected insulation, this is a job for professionals.
  • Dry out the affected area - use fans, a dehumidifier, and open windows to allow for air circulation and faster drying;
  • Disinfect - all areas affected by the leak/flooding after the area has dried out;
  • Prevent further mould growth - apply Concrobium throughout the affected area according to directions and let it dry overnight. This will prevent any mould from growing, providing continued resistance.
  • Dispose of damaged items responsibly. 

Speak to an Insulation Professional in Kitchener or Oakville for Insulation Removal 

If you have concerns about your insulation, air leaks or moisture and mould, contact Reitzel Insulation for insulation removal in Kitchener-Waterloo, Oakville, and other cities in Southern Ontario.


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