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Seal tight, ventilate correctly

I want to seal air leaks in my home to keep out cold air, but a neighbor mentioned that I could seal it too much and cause ventilation problems. Is this true?—Tricia

You would not think it’s possible, but you can seal up a home so tightly that it has little ventilation, which can contribute to indoor air quality problems or a buildup of moisture. The first step is to eliminate or reduce indoor air pollutants, such as smoke or chemicals. After that, bring in a contractor or energy auditor to inspect your home for leaks and seal them as much as possible.

After sealing, the contractor can measure the resulting air infiltration rate and advise whether to install mechanical ventilation.

Mechanical ventilation systems allow for controlled air movement and a consistent rate of ventilation, helping ensure good indoor air quality and moisture levels. Generally, well-sealed newer houses and manufactured homes have the greatest need for mechanical ventilation.

Ventilation varieties

There are two primary categories of mechanical ventilation: spot and whole-house. Spot ventilation systems are the fans above your oven range, in your laundry room, and in your bathroom that remove moist air and indoor air pollutants at the source. Generally, these fans work only when you turn them on, but you can install condensation sensors or humidistats so the fans will turn on whenever they sense a higher moisture content in the air.

Whole-house ventilation uses fans to circulate air throughout the home and introduces the right amount of outside air. These include exhaust ventilation systems that pull air out of your home and supply ventilation systems that bring outside air into the home. Balanced ventilation systems do both, while energy recovery ventilation systems combine fans with heat exchangers to modulate the temperature and humidity of air coming into  your home.

Determining which whole-house method is best for you will depend on your home’s needs, your budget, and your climate.

Mechanical ventilation, many variables

If mechanical ventilation is recommended, there is no simple way to determine how much of it your home will need. It depends on a combination of factors, including the rate of airflow into your home, the climate in your area, the layout and occupancy of your house, and whether there are other indoor air quality concerns, such as radon or combustion appliances like gas furnaces.

Patrick Keegan and Amy Wheeless for the December 2016 issue

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