Elevator shaft pressurization for smoke control in tall buildings: The Seattle approach

CONTAM simulations of both commercial and residential tall building models are conducted in order to study recently adopted Seattle code requirements for elevator shaft pressurization systems. In contrast to the International Building Code (IBC) requirements, the Seattle approach specifies across elevator door pressure minimums and maximums on only four “fire floors” (including one above, and two below, the fire floor). This is accomplished using a minimal pressurization of the entire elevator shaft in conjunction with venting of the four fire floors. The present study adresses the feasibility of calibrating such a system to meet the design objectives in tall buildings (system performance during an actual fire event is not considered). The two building models correspond to 37 story buildings with dual elevator and dual stairwell shafts extending the entire height of the building. Each model is calibrated to experimental data. Simulations are conducted for a variety of ambient temperatures and exterior building door positions. Coupled pressurization of the stairwells is also considered. The system requirements are found to be achievable for both elevator only and coupled elevator and stairwell pressurization systems. However, the observed pressure differences do change with changes in the ambient temperature as well as changes in the ground floor exterior door position. It is therefore recommended that such systems should be calibrated for pressure differences intermediate to the prescribed minimum and maximum values to compensate for changes to the system performance. Providing a relief vent to ambient on any recall floor may also be advisable.