Jan26th

A Breath of Fresh Air: Ventilation Matters

Breath of Fresh Air When creating an energy-efficient, airtight home through air sealing techniques , it’s very important to consider ventilation. Unless properly ventilated, an airtight home can seal in indoor air pollutants. Ventilation also helps control moisture —another important consideration for a healthy, energy-efficient home.

Purpose of Ventilation

Your home needs ventilation—the exchange of indoor air with outdoor air—to reduce indoor pollutants, moisture, and odors. Contaminants such as formaldehyde, volatile organic compounds, and radon can accumulate in poorly ventilated homes, causing health problems. Excess moisture in a home can generate high humidity levels. High humidity levels can lead to mold growth and structural damage to your home.

To ensure adequate ventilation, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) says that a home’s living area should be ventilated at a rate of 0.35 air changes per hour or 15 cubic feet per person per minute, whichever is greater.

There are three basic ventilation strategies:

1. Natural ventilation occurs when there is uncontrolled air movement or infiltration through cracks and small holes in a home—the same ones you want to seal to make your home more energy efficient. Opening windows and doors also provides natural ventilation. Because of central heating and cooling systems, however, most people don’t open windows and doors as often. Therefore, air infiltration has become the principal mode of natural ventilation in homes.

A home’s natural ventilation rate is unpredictable and uncontrollable—you can’t rely on it to ventilate a house uniformly. Natural ventilation depends on a home’s airtightness, outdoor temperatures, wind, and other factors. Therefore, during mild weather, some homes may lack sufficient natural ventilation for pollutant removal. Tightly sealed and/or built homes may have insufficient natural ventilation most of the time, while homes with high air infiltration rates may experience high energy costs.

2. Spot ventilation can be used to improve the effectiveness of natural ventilation. However, if both spot and natural ventilation together don’t meet your home’s ventilation needs, then you should consider a whole-house ventilation strategy. Spot ventilation improves the effectiveness of other ventilation strategies—natural and whole-house —by removing indoor air pollutants and/or moisture at their source.

Spot ventilation includes the use of localized exhaust fans, such as those used above kitchen ranges and in bathrooms. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends intermittent or continuous ventilation rates for bathrooms and kitchens instead of using windows (natural ventilation): 50 or 20 cubic feet per minute for bathrooms, and 100 or 25 cubic feet per minute for kitchens, respectively.

3. The decision to use Whole-House Ventilation is typically motivated by concerns that natural
ventilation
won’t provide adequate air quality, even with source control by spot ventilation .

Whole-house ventilation systems provide controlled, uniform ventilation throughout a house. These systems use one or more fans and duct systems to exhaust stale air and/or supply fresh air to the house. There are four types of systems:

Exhaust ventilation systems : Force inside air out of a home.

Supply ventilation systems : Force outside air into the home.

Balanced ventilation systems : Force equal amounts quantities of air into and out of the home.

Energy recovery ventilation (ERV) systems : Transfer heat and cool from
incoming or outgoing air to minimize energy loss.

Moisture Control Matters

Properly controlling moisture in your home will improve the effectiveness of your air sealing and insulation efforts, and vice versa. Thus, moisture control contributes to a home’s overall energy efficiency.

The best strategy for controlling moisture in your home depends on your climate and how your home is constructed. Before deciding on a moisture control strategy for your home, you may first want to understand how moisture moves through a home .

Moisture control strategies typically include the following areas of a home:

In most U.S. climates, you can use vapor diffusion retarders in these areas of your home to control moisture.

Source: US Dept. of Energy Consumer’s Guide to Energy Efficiency

If this information doesn’t scare you into hiring an experienced professional, nothing will. Click here to find a professional in your area who can assist you in building a tight, energy efficient, and properly ventilated home.

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