Fungal contamination and mould can occur in homes and concealed building enclosure assemblies if the materials are exposed to elevated relative humidity levels (typically above 80% RH for extended periods) and/or condensation. Organic materials, such as paper-faced drywall and wood, are susceptible to fungal growth in the home. Fungal growth is also common in bathrooms, but easily removed by regular household cleaning. Fungal growth on window frames may occur if there is excessive condensation due to high indoor relative humidity levels. Fungal growth is also commonly found in crawlspaces, attics, and other damp spaces as a result of elevated relative humidity levels, condensation, rainwater, and plumbing and appliance leaks.

Depending on the severity and duration of the wetting, fungal growth can lead to decay and deterioration of wood components. Moisture-damaged wood is somewhat common in many B.C. homes and is often discovered during weatherization work.

If significant fungal contamination or mould is present or suspected in the home, it must be removed and cleaned and the contributing source addressed prior to any air sealing and insulation weatherization work. To control and reduce the potential for mould growth, indoor moisture sources and indoor humidity must be controlled. This can be achieved by the combination of a proper ventilation system with good distribution in the home, and source moisture control. Additional information can be found in the Guide entitled Keeping the Heat In, published by Natural Resources Canada (see Resources at the end of this Guide). A good reference on wood durability, including procedures for the remediation of moisture-damaged wood buildings, can be found at the Binational Softwood Lumber Council website www.softwoodlumber.org.

Where mould growth is severe or moisture damage is extensive, a professional specializing in mould clean-up and structural repair should be retained. The document Guidelines on Assessment and Remediation of Fungi in Indoor Environments, published by the New York City Department of Heath and Mental Hygiene, is a good reference for remediation procedures. When cleaning up mould-contaminated building materials, WorkSafeBC occupational health and safety regulations should be followed.