A variety of health effects ranging from more common allergic reactions, to asthma attacks, and hypersensitivity pneumonitis’s can caused by too much moisture in a home. Excess moisture can be in the form of high relative humidity including humidity generated by people and their activities such as showers, cooking, or drying clothes. Water can also come from plumbing leaks, wet boots, or splashing around sinks. Moisture can travel with infiltrating outdoor air (or exhilarating indoor air) through the building shell, including the foundation. In addition to health problems, high relative humidity or water that enters building cavities that is not allowed to dry quickly can lead to problems such as rot, structural damage, and premature paint failure.
So how do we manage the moisture?
1. Manage water outside the foundation walls.
Test any underground drains with a hose to make sure they are working properly. Drains that are not working should be repaired or replaced with an elbow discharge described above.
2. Use construction techniques to control water, air movement, vapor diffusion, and condensation. Use construction methods and materials which promote the drying of building assemblies.
Use construction techniques which reduce the likelihood that warm, moist air will come in contact with cold surfaces, leading to condensation, mold growth, and rot. This includes controlling air movement and using vapor barriers on the warm side of walls and roofs.
It is important that the roof and flashing details and construction effectively keep water out of the house. It is also important that the roof and attic design addresses the issue of moisture in the form of water vapor to avoid condensation in building cavities.
4. Ensure the home is properly ventilated, with at least exhaust fans in the bathroom and kitchen and preferably a mechanical ventilation system designed to ventilate the entire house.
Using exhaust fans in the bathrooms and kitchen can remove much of the moisture that builds up from everyday activities and help to keep humidity below 50%. Another benefit to using kitchen and bathroom exhaust fans is that they can also exhaust odors and pollutants from these rooms. These fans can be part of an active ventilation system for the entire house, and help to reduce humidity levels. Vent bathroom, kitchen, and clothes dryer/laundry room exhausts directly to the outside, not into an attic or other enclosed space.