Photo Source: Summerhill

Implications of Improper Installation or failure:

If an air barrier is damaged, penetrated, or not completely sealed around the entire building envelope, this can allow outside air to enter and inside air to exit. This will greatly increase heat loss and cause the home to be less energy efficient, reducing the airtightness, and making the house drafty, and possibly causing moisture damage as air carries moisture with it.

The Simple Truth: The air barrier protects the entire building from air infiltration and exfiltration through the building envelope.