Building Airflow Modeling for Design of Pressurization · PDF fileBuilding Airflow Modeling...

Building Airflow Modeling for Design of Pressurization Systems High Rise Hotel • New York, NY

www.haifire.com www.haifire.com

30-story high rise hotel

New construction

Fully sprinklered

Two (2) pressurized fire-rated stairwells

Four (4) pressurized elevator hoistways


Smoke Management Objectives

Meet code requirements and design objectives for multiple smoke control systems

• Stairwell pressurization within 0.15 – 0.35 in H2O

• Elevator pressurization within 0.10 – 0.25 in H2O

• Corridor and Public Space Smoke Exhaust

• Eight (8) air change per hour exhaust

• Six (6) air change per hour supply


Typical Floor Plan (Most Floors)

Elevators Stairs


Open Floor Plan (Floors 5 and 25)

Elevators Stairs


Approach

Perform computer modeling to determine minimum fan capacities required for satisfactory pressurization under a range of conditions.

• CONTAM Building Airflow model, developed at NIST


Smoke Control Modeling Inputs

Stair and Elevator Pressurization (Supply)

Corridor Purge (Exhaust)


Challenge

Elevator and stair pressurization create competing forces.

Typical Floor

Open Layout Floor

Differences in airflow resistance on the typical floors compared to the open layout floors provides an engineering challenge.


Challenge

Pressurized air follows the path of least resistance.

Relatively high architectural leakage on the open layout floors (Floors 5 and 25) results in high differential pressures across the stair and elevator doors on these floors.


Solution

Developed a “hybrid” approach:

• Air capacities supplied to the stair and elevator shafts are reduced to provide a minimum differential pressure of 0.05 in. W.G. on all floors (minimum allowable pressure difference across smoke barriers per IBC).

• The capacity of the corridor exhaust is increased to provide higher differential pressures on the fire floor (meeting local code requirements).

The proposed smoke control system was verified under a range of architectural leakage assumptions and a range of outside temperatures.


Solution


Results

Modeling showed satisfactory pressurization would not be achievable on all floors due to the differences in architectural leakage on the open layout floors (Floors 5 and 25).

Developed and tested a solution involving a hybrid approach using different design pressures for the non-fire and fire floors

The solution resulted in:

• Minimal mechanical and architectural changes to the building.

• Reduced fan sizes needed for stair and elevator pressurization.

• Eliminating unsafe door opening force conditions.

• Meeting local code requirements on the fire floor while maintaining the minimum pressure differential for smoke barriers on the non-fire floors.

www.haifire.com

Michael J. Ferreira, PE Principal

410-737-8677 x284 [email protected]

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