As of 2003, Pennsylvania adheres to the current International Residential Code regulations, so windows and exits must meet the current IRC egress criteria. Contact your local township to verify current code and regulations, and to obtain any necessary building permits.
In construction, egress refers to the way in which inhabitants can escape from a building in an emergency situation. A window that meets IRC egress requirements is considered an acceptable means of escape. It is also a means for emergency personnel to enter the building if necessary.
IRC requirements mandate that windows have an open minimum width of 20 inches and an open minimum height of 24 inches. However, together the two must equal a total net window clearance of at least 821 inches (5.7 square feet) when multiplied together. If the egress window is on the ground floor, a net clearance of 5 square feet or greater is required. In addition, the window sill must be no higher than 44 inches from the floor.
The window must be able to open fully without any obstructions and without the need for a key or tool to be considered egress. If a basement window has a window well, other egress requirements must be met, such as the well must be at least 9 square feet, and if the well is deeper than 44 inches, a permanent ladder or stairway must be in place.