Defining Air Infiltration

To some extent, every home, regardless of age or location, needs to “breathe.” You may feel some air coming into your home around windows, doors, skylights, electrical outlets, walls, floors or the roof. This is air infiltration, and it is the result of air pressure differences between the inside and outside of the home. Every home has some level of air infiltration. Glass surface temperature, by itself, is not an indication of air infiltration.

Product Types

Different types of products allow different air infiltration rates. For example, fixed products – those that do not open (such as a picture window) – are the most airtight. Those that do open, like casements (commonly referred to as crank-out windows) or double- or single-hung windows that open vertically have the most potential for air infiltration. This is due to design tradeoffs that allow the units to open and close using reasonable effort to move them.

If your windows open, be sure to keep them closed and locked when not being used for ventilation. This will help reduce air infiltration to keep your home warmer in the winter and cooler in the summer.

Location Matters

Your home’s location and climate can impact air infiltration. That’s why it’s important to select the right type of window, door or skylight for your home’s climate conditions and install it properly according to the manufacturer’s instructions.

Different placement of products throughout the home allow for varying air infiltration rates. For example, a window placed on a north wall facing harsh arctic winter winds should have different qualities to help protect from the cold winds as compared to a southern-facing window overlooking a sunny beach. A skylight, because it is roof mounted, is also impacted by location as well as the slope of the roof surface on which it is installed.

No single product design is best for every application. Depending on the direction a wall or roof faces and the local climate, windows, doors and skylights may need to be different from one area to another within a home.

Air Infiltration Testing

Check with the manufacturer to see if a sample of your windows, doors and skylights has been tested to determine they meet industry requirements for air infiltration. To pass this test (as detailed in the industry standard - AAMA/WDMA/CSA 101/I.S.2/A440), a residential product must not allow more than 0.3 cubic feet of air to pass through the entire manufactured unit per minute, per square foot. At an accredited test laboratory, a new product sample is subjected to constant air pressure to simulate 25 mph winds, which represents a time-averaged weather condition. Since air flow depends upon temperature and barometric pressure, these are taken in account to determine total air infiltration.

For more details, visit the Residential Air Infiltration Frequently Asked Questions page.