Tampa Bay Home Inspector Blog

The most serious consequence of an improper ventilation setup is the potential accumulation of mold in attics or crawlspaces.   Health problems caused by mold are related to high concentrations of spores in indoor air. “Spores” are like microscopic seeds, released by mold fungi when they reproduce.  Every home has mold.  Moisture levels of about 20% in materials will cause mold colonies to grow.  Inhaling mold spores can cause health problems in those with asthma or allergies, and can cause serious or fatal fungal infections in those with lung disease or compromised immune systems.

In order to grow, mold fungi require that the following conditions are present:

Improper Install on Bathroom Vent.

• Oxygen
• Temperatures between approximately 45° F and 85° F
• Food.  This includes a wider variety of materials found in homes
• Moisture

If insufficient levels of any of these requirements exist, all mold growth will stop and fungi will go dormant. Most are difficult to actually kill.
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.  Read the rest of this entry »

Bathroom ventilation systems are designed to exhaust odors and moist air to the home’s exterior. Typical systems consist of a ceiling fan unit connected to a duct that terminates at the roof.

Bathroom ventilation fans should be inspected periodically for dust buildup that can impede airflow. Particles of moisture-laden animal dander and lint are attracted to the fan because of its static charge.

The most common defect related to bathroom ventilation systems is improper termination of the duct. Vents must terminate at the home exterior. The most common improper terminations locations are:

• Mid level in the attic space
• Beneath the insulation
• Below the attic ridge or roof vents

Improperly terminated ventilation systems may appear to work fine from inside the bathroom; you have to look in the attic or on the roof. Sometimes poorly-installed ducts will loosen or become disconnected at joints or connections.

Ducts which leak or terminate in attics can cause problems from condensation. Warm, moist air will condense on cold attic framing, insulation or other materials. This condition has the potential to cause health or decay problems from mold, or to damage materials such as drywall. Moisture also reduces the effectiveness of thermal insulation.

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