Warehouse Ventilation

[Mech]

2009 IMC

565,000 sf warehouse building w/ approximately 130 tractor trailer loading docks

40,000 cfm make-up air

The mechanical contractor is proposing to pressurize the space with 100% outside air units and no exhaust fans or dampers. Make-up air is introduced at the ceiling (roof) w/ a 45 degree angled nozzle. The assumption is air will leak out (be pushed out) of the building through cracks and the loading dock doors.

What zone air distribution effectiveness factor should be used? I am thinking 1.0 since there is no return air.

Thanks

TABLE 403.3.1.2 ZONE AIR DISTRIBUTION EFFECTIVENESSa,b,c,d,e

Air Distribution Configuration	Ez
Ceiling or floor supply of cool air	1.0f
Ceiling or floor supply of warm air and floor return	1.0
Ceiling supply of warm air and ceiling return	0.8g
Floor supply of warm air and ceiling return	0.7
Makeup air drawn in on the opposite side of the room from the exhaust and/or return	0.8
Makeup air drawn in near to the exhaust and/or return location	0.5

For SI: 1 foot = 304.8 mm, 1 foot per minute = 0.00506 m/s, °C = [(°F) – 32]/1.8.

a. "Cool air" is air cooler than space temperature.

b. "Warm air" is air warmer than space temperature.

c. "Ceiling" includes any point above the breathing zone.

d. "Floor" includes any point below the breathing zone.

e. "Makeup air" is air supplied or transferred to a zone to replace air removed from the zone by exhaust or return systems.

f. Zone air distribution effectiveness of 1.2 shall be permitted for systems with a floor supply of cool air and ceiling return, provided that low-velocity displacement ventilation achieves unidirectional flow and thermal stratification.

g. Zone air distribution effectiveness of 1.0 shall be permitted for systems with a ceiling supply of warm air, provided that supply air temperature is less than 15°F above space temperature and provided that the 150 foot-per-minute supply air jet reaches to within 41/2 feet of floor level.

 

[Keystone]

Take it with a grain of salt, I am working toward my Comm Mech Insp & Examiner now. I would agree with 1.0