ASHRAE-Standard-55 - Page 059

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is less than 10°C (50°F) or greater than 33.5°C (92.3°F), this option may not be used, and no specific guidance for such conditions is included in this standard.

Figure 5-9 accounts for local thermal discomfort effects in typical buildings, so it is not necessary to address these factors when using this option. If there is reason to believe that local thermal comfort is a problem, it is acceptable to apply the criteria in Section 5.3.5.

Figure 5-9 also accounts for people’s clothing adaptation in naturally conditioned spaces by relating the satisfactory range of indoor temperatures to the outdoor climate, so it is not necessary to estimate the clothing values for the space. No humidity or air speed limits are required when this option is used.

Figure 5-9 includes the effects of people’s indoor air speed adaptation in warm climates, up to 0.3 m/s (59 fpm) in operative temperatures to warmer than 25°C (77°F). In naturally conditioned spaces where air speeds within the occupied zone exceed 0.3 m/s (59 fpm), the upper satisfactory temperature limits in Figure 5-9 are increased by the corresponding  t 0 in Table 5-12, which is based on equal SET values as illustrated in Section 5.3.4. For example, increasing air speed within the occupied zone from 0.3 m/s (59 fpm) to 0.6 m/s (118 fpm) increases the upper satisfactory temperature limits in Figure 5-9 by a  t 0 of 1.2°C (2.2°F). These adjustments to the upper satisfactory temperature limits apply only at t 0 > 25°C (77°F) in which the occupants are engaged in near sedentary physical activity (with metabolic rates between 1.0 met and 1.3 met).

ANSI/ASHRAE Standard 55-2023 57