ASHRAE-Standard-55 - Page 056

Extracted Content

Section 5.3.6.3 specifies the maximum change in operative temperature to allowed during a period of time. For any given time period, the most restrictive requirements from Table 5-11 apply. For example, the operative temperature may not change more than 2.2°C (4.0°F) during a 1.0 hour period, and it also may not change more than 1.1°C (2.0°F) during any 0.25 hour period within that 1.0 hour period. If the user creates variations as a result of control or adjustments, higher values may be acceptable.

These local thermal comfort criteria were developed in order to keep the expected percent of occupants who are dissatisfied due to all of these local discomfort factors at or below 10%. The operative temperature to ranges required in the standard were developed in order to keep the predicted percent dissatisfied of occupants due to operative temperature only, without factoring in local thermal factors. When both local discomfort factors and operative temperature considerations are combined, the goal of this standard to standardize satisfactory thermal conditions for a substantial majority of occupants (80%) is achieved. This is especially true if there is some overlap between those who are dissatisfied due to local factors and those who are dissatisfied due to operative temperature.

54 ANSI/ASHRAE Standard 55-2023