Home Energy Losses: Air Leakage and Air Sealing


Air Leakage and Energy Losses

Many houses, in particular the older ones, tend to be very leaky. And this can cost highly: according to EPA studies, in a typical American house air leakage accounts for between 25 percent and 40 percent of the energy used for heating and cooling.

Air leakage is indeed a cause of higher energy bills, low comfort, moisture, cold drafts, unwanted noise and lower indoor air quality or lower building durability. And air sealing one of the most crucial elements of an energy efficient building.

Sealing all horizontal and vertical construction joints should be considered a common practice in home building.

See also:
Windows and doors Weatherstripping
Windows and doors Caulking


Air Leakage Tests in existing homes

Leakage tests may be important when remodeling. Tests will help you decide the right approach concerning key factors as windows replacement, duct improvements or walls insulation. Tests will also help you on decisions concerning new heating or cooling equipment.

So, consider an air leakage test. They are cheap, quick (usually performed in a few hours time: 2-4 hours) and very common. They are based in «blower doors» and «duct blowers» equipment, and allow to measure the leakiness of buildings and ductwork and to locate the source of leaks.


New Houses Air Sealing

Many air leakage paths are difficult and costly to access and properly seal in existing homes.

So, if building a house, consider including the right air sealing. With a minimal investment, you will save energy and increase comfort and air quality…

Air Leakage Paths

Air leakage typically occurs at several common locations, namely:

-  joints between building materials
- gaps around doors and windows frames
- bottom of walls, in the joints with the floor/foundation
- penetration linked to piping, ducts...
- attic penetrations: in the ceiling plane, and in ducts holes, pipes and chimneys joints.

These last paths involve the most important air-sealing areas, because these air leakage sources tend to be relatively large and because the hot air tends to rise and to flow to the top of the house, escaping by it whenever possible. Air sealing windows and door is a good practice, but sealing attic penetrations is usually the most important feature of home air sealing.


Materials used in Air Sealing

There are many products available in the market for air sealing. They include caulks, expanding foams, weather-stripping, gaskets, door sweeps...  Densely installed insulation is also an effective way of reducing air leakage through walls and ceilings, while polyethylene can be installed as an air and vapor barrier.

Air leakage and mechanical ventilation

Air sealing your house is undoubtedly one of the most effective ways to save energy, but airtight homes need also adequate ventilation, and that means mechanical ventilation in most climates and days to maintain good indoor air quality.

Homes need minimum amounts of air exchange in order to provide oxygen for their residents, to control humidity, to eliminate odors, and so on. And very few homes have the ability to truly control ventilation rates. In some cases and when the weather is favorable, you may open the windows or profit from natural ventilation. But in most homes and weather conditions, houses that are tightly sealed demand active ventilation - exhaust fans, heat recovery ventilators… - to ensure that fresh air is provided. In cold climates, and in houses without a good natural ventilation, if you have implemented an highly sealed approach to your home, you should talk with your heating/cooling contractor about installing an energy recovery ventilation system. It is essential to regulate fresh air entries, humidity and minimize energy losses.






See also:
Energy Efficient House Basics
Good and bad Indoor Air quality
Mechanical ventilation: HEV and HRV
Natural Ventilation: cross and stack


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