These factors include insulation materials that prevent air infiltration, such as open-cell spray foam insulation, calking framing joints, and sealing gaps around windows/doors. Arbor Insulation's spray foam product and energy seal option helps you create homes and buildings that well sealed against air leakage. For a more detailed article from the DOE Energy Star progam see below:

Air Leakage - DOE arictle on controlling air leakage is available for download.