Smoke Control and High-Rise Office Buildings with Operable Windows: Two Case Studies

Headnote

ABSTRACT

This paper describes the smoke control aspects of two naturally ventilated high-rise office buildings with operable windows. One utilizes its operable windows in conjunction with an HVAC system to provide tenants with fresh air. The other utilizes a series of automatically controlled windows and vents in conjunction with tenant-controlled windows to provide ventilation. Both buildings, located in San Francisco, were designed under the Uniform Building Code.

INTRODUCTION

Due to the moderate San Francisco climate, naturally ventilated high-rise office buildings are becoming popular again in San Francisco. This paper describes the smoke control aspects of two such buildings: one that houses the headquarters of a private company, and a second that houses various government agencies (Federal Building). The headquarters building utilizes its operable windows in conjunction with an HVAC system to provide tenants with fresh air. The San Francisco Federal Building utilizes a series of automatically controlled windows and vents in conjunction with tenantcontrolled windows to provide the primary means of ventilation for the building. The smoke control systems of both buildings were designed under the Uniform Building Code with similar goals but significantly different results.

OFFICE BUILDING

The Gap World Headquarters building is a 15-story office building with an atrium lobby in downtown San Francisco. The building faces the San Francisco Bay on the east while the other three sides face an urban setting. The upper floors receive the primary ventilation through standard HVAC units, which move air through shafts to each level. Supply air is provided through an underfloor plenum. Return air is through an above-ceiling plenum. The operable windows consist of 3foot (0.9 m) wide by 2-foot (0.6 m) tall windows that are hinged at the bottom. The windows open a maximum of 4 inches (100 mm). The implicit goals of the system included life safety and property protection.

The design team evaluated several smoke control options, including a passive smoke control approach, the exhaust method with each floor as a zone, the pressurization approach, and a hybrid approach that would act as a pressurization system except when the windows are opened, when it would act as an exhaust system. Due to the City of San Francisco requirements for a mechanical smoke control system, the passive approach was eliminated.

Exhaust Approach