ASHRAE-Standard-55 - Page 016
Extracted Content
Figure 5-4 Satisfactory ranges of operative temperature to and average air speed Va for 1.0 and 0.5 clo comfort zones at humidity ratio 0.010.
Figure 5-5 provides a graphical example of comfort zones for two air speeds. Direct use of this chart to comply with the standard is allowable for the specific input conditions described on the chart.
Figure 5-6 describes the steps for determining the limits to air speed inputs. 5.3.4.1 Average Air Speed Va with Occupant Control. Section 5.3.4.2 does not apply when the occupants have control over average air speed Va and one of the following criteria is met:
a. One means of control exists for every six occupants or fewer. b. One means of control exists for every 84 m [2] (900 ft [2] ) or less. c. In multioccupant spaces where groups gather for shared activities, such as classrooms and conference
rooms, at least one control shall be provided for each space, regardless of size. Multioccupant spaces that are subdivided by movable walls shall have one control for each space subdivision.
5.3.4.2 Average Air Speed Va without Occupant Control. If occupants do not have control over the local air speed, meeting the requirements of Section 5.3.4.1, the following limits apply to the SET model and to Figure 5-4.
a. For operative temperatures to above 25.5°C (77.9°F), the upper limit to average air speed Va shall be 0.8
m/s (160 fpm). b. For operative temperatures to between 23.0°C and 25.5°C (73.4°F and 77.9°F), the upper limit to average
air speed Va shall follow an equal SET contour as described in Normative Appendix D. In Figure 5-4, this curve is shown between the dark and light shaded areas. It is permitted to determine the curve in Figure 5-4 by using the following equation:
Va = 50.49 – 4.4047( to ) + 0.096425( to ) [2] (m/s, °C)
Va = 31375.7 – 857.295( to ) + 5.86288( to ) [2] (fpm, °F)
c. For operative temperatures to below 23.0°C (73.4°F), the limit to average air speed Va shall be 0.2 m/s
(40 fpm). Exceptions to (c):
- Representative occupants with clothing insulation Icl greater than 0.7 clo.
- Representative occupants with metabolic rates above 1.3 met. Informative Note: These limits are shown by the light gray area in Figure 5-4.
14 ANSI/ASHRAE Standard 55-2023