The Chicago-based Council on Tall Buildings and Urban Habitat has come out against a proposed change to the 2009 International Building Code that would require skyscrapers of a height of 420 feet or more to have three exit stairwells. The proposal, recently approved by the International Code Council, comes out of the National Institute of Standards and Technology's investigation into the 2001 collapse of the World Trade Towers in New York City. The NIST came up with a list of 30 recommendations, including increasing the bonding strength of fireproofing of structural steel by up to a factor of seven, photoluminescent markings of exit paths, and recommendation 17, which mandates the third stairwell to expedite evacuation while separating occupants fleeing the building from firefighters entering the building to battle the emergency. That recommendation is now part of the proposed 2009 IBC.
CTBUH claims the change would not improve safety, but "if applied to many current or proposed schemes, would make them economically unviable and could de-value existing tall building stock." It classifies the proposal as "an outdated method for designing tall or complex buildings. A performance based approach where one tests the design against a set of functional aims using risk based and engineering analyses is the preferred solution internationally and will lead to buildings where the level of safety is demonstrated to be adequate, not assumed to be acceptable." The new IBC would set new safety standards that would likely be incorporated into local building codes of individual municipalities.