Indoor Air Pollution is in the top 5 environmental risks to public health (EPA). It is estimated 30% – 50% of all structures have damp conditions encouraging the growth of mold.

Controlling moisture inside your environment
Since mold only grows where there is moisture, it must be controlled. According to The American Society of Home Inspectors in 2002, “about 38% of homes have mold and fungus growth due to elevated moisture.” Elevated moisture can come from leaks, flooding or hurricanes, condensation on cold surfaces or too much humidity. Leaks from windows, roofs, or pipes must be inspected to insure they are properly repaired or replaced. If there has been water intrusion, it must be dried properly within 48 hours to insure mold growth does not occur. This would also include using a dehumidifier to remove moisture in the air. Although building defects like roof leaks, or ruptured pipes are considered the main sources for too much moisture in schools, it is more commonly the fresh air ventilation to blame. Unlike a residential ventilation system, in public spaces there are “fresh air” requirements by ASHRAE (American Society of Heating) Simply put, public buildings are required to have a percentage of outside air enter a space. Water brought into a building through ventilation is sufficient to sustain mold growth, unless the air conditioner is equipped to handle this excess moisture. Delayed maintenance or insufficient maintenance are also associated with moisture problems in schools and large buildings. Fixing the building defects alone may not be enough. You must control the relative humidity within a space in order to control mold growth.

What is relative humidity and how do you measure it? Relative humidity is the ratio of the amount of water vapor actually present in the air to the greatest amount possible at the same temperature. By using a moisture meter or hygrometer, you can check the relative humidity within your environment. A hygrometer is an inexpensive (usually $50.00 or less) item that measures the temperature and relative humidity in a space and available in most hardware stores. Since mold will grow in humidity levels between 65% – 99%, it is recommended to have the relative humidity within a space to be below 60%, ideally below 50%. In northern climates during the winter months the recommendation is between 30% – 40% to prevent condensation build up on windows and other surfaces. According to the American Lung Association and U.S.Consumer Product Safety Commission, one third of all structures have damp conditions that may encourage development of pollutants such as mold and bacteria, which can cause allergic reactions -including asthma- and spread infectious diseases.
What if your relative humidity is higher than 60% after repairing building defects? Once you determine your relative humidity is too high, there are solutions available to correct the problem. If all building defects have been repaired, it may be the ventilation system that is not adequately drying out the space. This can be determined by a HVAC expert or Indoor Air Specialist.
A dehumidifier will control excess humidity within a space, but may only be a temporary answer. The HVAC system should be modified or replaced to properly control the moisture within the environment. There are instances where the HVAC system installed has been incorrectly “over-sized” for a space and will never be able to do the proper job of controlling the humidity. There are other times when the lack of maintenance has damaged the system. Dehumidifiers may be necessary in addition to the HVAC system in schools and office buildings located in geographically hot, humid locations.
Routine activities such as cooking, laundering and bathing also adds to moisture within a home. Exhaust fans will help regulate the moisture levels within areas where these activities are located. Clothes dryers should also be exhausted to the exterior of the building. Concrete slabs are a large source of moisture. The average basement lets in 18 gallons of moisture each day. By properly sealing the concrete against water migration, the problem may be resolved without the use of a dehumidifier.