Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.
It is unwise to rely on air leakage for ventilation because it can't be controlled. During cold or windy weather, too much air may enter the house. When it's warmer and less windy, not enough air may enter. Air infiltration also can contribute to problems with moisture control. Moldy and dusty air can enter a leaky house through such areas as attics or foundations. This air in the house could cause health problems.
The recommended strategy in both new and old homes is to reduce air leakage as much as possible and to provide controlled ventilation as needed.
Note that air sealing alone can't replace the need for proper insulation throughout your home, which is needed to reduce heat flow.
You can reduce your home's heating and cooling costs through proper insulation and air sealing techniques. These techniques will also make your home more comfortable.
Any air sealing efforts will complement your insulation efforts, and vice versa. Proper moisture control and ventilation strategies will improve the effectiveness of air sealing and insulation, and vice versa.
Therefore, a home's energy efficiency depends on a balance between all of these elements:
A proper balance between all of these elements will also result in a more comfortable, healthier home environment.
You need insulation in your home to provide resistance to heat flow. The more heat flow resistance your insulation provides, the lower your heating and cooling costs.
Heat flows naturally from a warmer to a cooler space. In the winter, this heat flow moves directly from all heated living spaces to adjacent unheated attics, garages, basements, and even to the outdoors. Heat flow can also move indirectly through interior ceilings, walls, and floors wherever there is a difference in temperature. During the cooling season, heat flows from the outdoors to the interior of a house.
To maintain comfort, the heat lost in the winter must be replaced by your heating system and the heat gained in the summer must be removed by your cooling system. Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat.
An insulation's resistance to heat flow is measured or rated in terms of its thermal resistance or R-value.
Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.
It is unwise to rely on air leakage for ventilation because it can't be controlled. During cold or windy weather, too much air may enter the house. When it's warmer and less windy, not enough air may enter. Air infiltration also can contribute to problems with moisture control. Moldy and dusty air can enter a leaky house through such areas as attics or foundations. This air in the house could cause health problems.
The recommended strategy in both new and old homes is to reduce air leakage as much as possible and to provide controlled ventilation as needed.
Note that air sealing alone can't replace the need for proper insulation throughout your home, which is needed to reduce heat flow.
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.
Proper ventilation should also be part of a moisture control strategy.
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.
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:
Uncontrolled air movement into a home through cracks, small holes, and vents, such as windows and doors. Not recommended for tightly sealed homes.
Controlled air movement using one or more fans and duct systems.
Controlled air movement using localized exhaust fans to quickly remove pollutants and moisture at their source. Typically used in conjunction with one of the other strategies.