ASHRAE-Standard-55 - Page 020
Extracted Content
Table 5-11 Limits on Temperature Drifts and Ramps
| Time Period, h | 0.25 | 0.5 | 1 | 2 | 4 |
|---|---|---|---|---|---|
| Maximum Operative Temperature****_to _Change Allowed, °C (°F) | 1.1 (2.0) | 1.7 (3.0) | 2.2 (4.0) | 2.8 (5.0) | 3.3 (6.0) |
Figure 5-9 Acceptable operative temperature to ranges for naturally conditioned spaces.
5.4 Determining Acceptable Thermal Conditions in Occupant-Controlled Naturally Conditioned Spaces (Adaptive Model)
5.4.1 Applicability. This method defines acceptable thermal environments only for occupant-controlled naturally conditioned spaces that meet all of the following criteria:
a. There is no mechanical cooling system (e.g., refrigerated air conditioning, radiant cooling, or desiccant
cooling) or heating system in operation. b. Representative occupants have metabolic rates ranging from 1.0 to 1.5 met. c. Representative occupants are free to adapt their clothing to the indoor and/or outdoor thermal conditions
within a range at least as wide as 0.5 to 1.0 clo. d. The prevailing mean outdoor temperature is greater than 10°C (50°F) and less than 33.5°C (92.3°F).
5.4.2 Methodology. The allowable indoor operative temperatures to shall be determined from Figure 5-9
using the 80% acceptability limits or the equations in Section 5.4.2.2.
Informative Note: The 90% acceptability limits are included for information only. See Informative Infor
mative Appendix J for further guidance.
5.4.2.1 The prevailing mean outdoor air temperature t pma out shall be determined in accordance with
all of the following.
5.4.2.1.1 It shall be based on no fewer than seven and no more than 30 sequential days prior to the day in question.
5.4.2.1.2 It shall be a simple arithmetic mean of all of the mean daily outdoor air temperatures
tmda out of all the sequential days in Section 5.4.2.1.1.
Exception to 5.4.2.1.2: Weighting methods are permitted, provided that the weighting curve continually
decreases toward the more distant days such that the weight applied to a day is between 0.6 and 0.9 of
18 ANSI/ASHRAE Standard 55-2023