Mold is impossible to identify visually and must be tested by a lab in order to be confidently labeled. Inspectors should refrain from calling anything “mold” but should refer to anything that appears as mold as a material that “appears to be microbial growth.” Inspectors should include in their report, and in the inspection agreement signed by the client, a disclaimer clearly stating that the General Home Inspection is an inspection for safety and system defects, not a mold inspection.
Decay, which is rot, is also caused by fungi. Incipient or early decay cannot be seen. By the time decay becomes visible, affected wood may have lost up to 50% of its strength.
In order to grow, mold fungi require the following conditions to be present:
- temperatures between approximately 45° F and 85° F;
- food. This includes a wider variety of materials found in homes; and
Even though mold growth may take place in the attic, mold spores can be sucked into the living areas of a residence by low air pressure. Low air pressure is usually created by the expulsion of household air from exhaust fans in bathrooms, dryers, kitchens and heating equipment.
Ventilation ducts must be made from appropriate materials and oriented effectively in order to ensure that stale air is properly exhausted.
Ventilation ducts must:
- terminate outdoors. Ducts should never terminate within the building envelope;
- contain a screen or louvered (angled) slats at its termination to prevent bird, rodent and insect entry;
- be as short and straight as possible and avoid turns. Longer ducts allow more time for vapor to condense and also force the exhaust fan to work harder;
- be insulated, especially in cooler climates. Cold ducts encourage condensation;
- protrude at least several inches from the roof;
- be equipped with a roof termination cap that protects the duct from the elements; and
- be installed according to the manufacturer's recommendations.
- be made from inflexible metal, PVC, or other rigid material. Unlike dryer exhaust vents, they should not droop; and
- have smooth interiors. Ridges will encourage vapor to condense, allowing water to back-flow into the exhaust fan or leak through joints onto vulnerable surfaces.