Important international building codes related to windows pertain to wind and impact resistance, energy efficiency, emergency escape, glazing and installation. International codes base required design load for vertical glazing in terms of wind on a building's location, its mean height and its exposure. International codes related to impact resistance distinguish between locations based on the identified threat to human life by wind borne debris and by type of building. Windows in hospitals require higher resistance levels than office buildings.
Windows must be tested and labeled according to code specifications for both wind and impact resistance. In some cases, exceptions are made, and for some residential buildings, protective wood panels are permitted in place of impact resistant glazing or shutters. International energy codes pertaining to windows establish maximum permitted U-factors, which represent the window's insulation level, and solar heat gain coefficients, which indicate how well a window blocks heat from the sun.
Emergency escape and rescue openings are required in all bedrooms below the fourth floor and in most basements. A normally operable window, meeting emergency requirements, is required by code to have an opening size of 24 inches high, 20 inches wide and either 5 or 5.7 feet in area. It must not require a key or special knowledge to open. Code also requires that the bottom sill of an operable window that is placed 72 inches or higher than the ground outside must be a minimum of 24 to 36 inches above the interior floor.