Windows and doors can be a significant source of air leakage, especially in older homes. Air leakage can not just occur at the joint between the window or door product and the wall, but also through the joints between the operable sashes and the fixed frame. While air leakage between the window and the wall is relatively easy to control, reducing air leakage through the joints of the product can be more challenging. Even well maintained windows and doors eventually need to be replaced due to age, usage, and exposure to weather. When it is not possible to address uncontrolled drafts, condensation, and operational problems, consider replacing the windows and doors.