Ventilation and Controlling Moisture In Your Home

Continued from Ventilation

Too much moisture in a home can lead to mold, mildew, and other biological growth. This in turn can lead to a variety of health effects ranging from more common allergic reactions, to asthma attacks, and hypersensitivity pneumonitits, for example. 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 exfiltrating 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.

Methods to control moisture include building an energy-efficient home with proper air-sealing, proper use of vapor barriers and vapor diffusion strategies. The entire building envelope, from the foundation to the roof, should be designed to not only prevent moisture entry, but also to allow any moisture which does enter a means to escape. As mentioned above, people and their activities in a home are big sources of moisture; thus proper ventilation is also important in order to maintain indoor humidity levels within an acceptable range.

Ventilation The Homeowner’s Guide to Ventilation.

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.

How Much Ventilation Do I Need?

In the past, no specific requirements for ventilation were imposed for residential buildings because leakage in envelope components and natural ventilation was considered adequate to maintain indoor air quality. As envelope construction practices have improved, the need to provide fresh air to homes via mechanical means has increased.

Minnesota Code Requirements for Mechanical Ventilation

Any single-family home built since April 2000 has to have a mechanical ventilation system.  Minnesota is one of the only states with this requirement because of the tight air sealing and insulation requirements.  Most builders use either an air exchanger or a continuously exhausting fan(s) to meet this energy code requirement.  Air exchangers can be heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs).

Minnesota homes are built under the motto “Build It Tight & Ventilate It Right.”  Your home needs you to run and maintain your mechanical ventilation system in order for it to operate correctly.  If you fail to do this, you could void the Home Warranty Law provisions provided under state law.  Your warranty does not cover “Loss or damage from dampness and condensation due to insufficient ventilation after occupancy.”  (327A.03 Exclusions)

Whether a mechanical ventilation system makes sense in your existing homes depends on the house, your existing heating, ventilation, and air-conditioning (HVAC) system, and the changes you have planned. You should discuss this with your Minnesota HVAC contractor.