ASHRAE+62.1-2022+(1) - Page 024
Extracted Content
Table 6-4 Zone Air Distribution Effectiveness ( Ez )
Air Distribution Configuration Ez
Well-Mixed-Air Distribution Systems
Ceiling supply of cool air 1.0
Ceiling supply of warm air and floor return 1.0
Ceiling supply of warm air 15°F (8°C) or more above space temperature and ceiling return 0.8
Ceiling supply of warm air less than 15°F (8°C) above average space temperature where the supply air-jet velocity is less than 0.8 150 fpm (0.8 m/s) within 4.5 ft (1.4 m) of the floor and ceiling return
Ceiling supply of warm air less than 15°F (8°C) above average space temperature where the supply air-jet velocity is equal to or greater than 150 fpm (0.8 m/s) within 4.5 ft (1.4 m) of the floor and ceiling return
1.0
Floor supply of warm air and floor return 1.0
Floor supply of warm air and ceiling return 0.7
Makeup supply outlet located more than half the length of the space from the exhaust, return, or both 0.8
Makeup supply outlet located less than half the length of the space from the exhaust, return, or both 0.5
Stratified-Air Distribution Systems (Section 6.2.1.2.1)
Floor supply of cool air where the vertical throw is greater than or equal to 60 fpm (0.25 m/s) at a height of 4.5 ft (1.4 m) above the floor and ceiling return at a height less than or equal to 18 ft (5.5 m) above the floor
Floor supply of cool air where the vertical throw is less than 60 fpm (0.25 m/s) at a height of 4.5 ft (1.4 m) above the floor and ceiling return at a height less than or equal to 18 ft (5.5 m) above the floor
Floor supply of cool air where the vertical throw is less than 60 fpm (0.25 m/s) at a height of 4.5 ft (1.4 m) above the floor and ceiling return at a height greater than 18 ft (5.5 m) above the floor
Personalized Ventilation Systems (Section 6.2.1.2.2)
1.05
1.2
1.5
Personalized air at a height of 4.5 ft (1.4 m) above the floor combined with ceiling supply of cool air and ceiling return 1.40
Personalized air at a height of 4.5 ft (1.4 m) above the floor combined with ceiling supply of warm air and ceiling return 1.40
Personalized air at a height of 4.5 ft (1.4 m) above the floor combined with a stratified air distribution system with nonaspirating floor supply devices and ceiling return
Personalized air at a height of 4.5 ft (1.4 m) above the floor combined with a stratified air distribution system with aspirating floor supply devices and ceiling return
provided such value is the product of the net occupiable area of the ventilation zone and the default occupant density listed in Table 6-1. 6.2.1.2 Zone Air Distribution Effectiveness. The zone air distribution effectiveness ( Ez ) shall be determined in accordance with Table 6-4 or Normative Appendix C.
Informative Notes:
- For some configurations, the default value depends on space and supply air temperature.
- Calculation of Ez using the procedures in Normative Appendix C may result in values greater than those listed in Table 6-4 for systems with the same description.
6.2.1.2.1 Stratified Air Distribution Systems. A stratified air distribution system shall be designed in accordance with the following subsections, or the zone air distribution effectiveness ( Ez ) shall be determined in accordance with Normative Appendix C.
6.2.1.2.1.1 Supply Air. Cool air shall be at least 4°F (2°C) less than the average room air temperature.
6.2.1.2.1.2 Return Air. The return air openings or pathways shall be located more than 9 ft (2.8 m) above the floor.
6.2.1.2.1.3 Stratification. The zone shall not contain any devices that mechanically mix the air, and shall be protected from impinging airstreams from adjacent ventilation zones.
Informative Note: Ceiling fans, blowers, air curtains, aspirating diffusers without adequate draft separation, or other devices that disrupt the stratification cause the zone air distribution effectiveness to be similar to a well-mixed system.
22 ANSI/ASHRAE Standard 62.1-2022
1.20
1.50