Egress windows are required to have, at the minimum, a 5.7-square-foot net clear opening with at least a 20-inch opening width and 24-inch opening height, states the Family Handyman and Boman Kemp websites. Some exceptions exist within building planning codes, but essentially, egress windows must be large enough for firefighters to enter and residents to escape in the event of a fire or other emergency.
Other requirements for egress windows include a maximum height of 44 inches from the ground to the bottom of the window and unobstructed accessibility, states Family Handyman. Emergency personnel must be able to access and enter the egress without the use of keys or other tools. For a full list of requirements and exceptions, review the International Building Code.