ASHRAE-Standard-55 - Page 007
Extracted Content
uniform environment; calculated in accordance with Normative Appendix A of this standard. (See ASHRAE Handbook—Fundamentals [ 1], Chapter 9, for further discussion of operative temperature.) temperature, plane radiant (tpr ): the uniform temperature of an enclosure in which the incident radiant flux on one side of a small plane element is the same as in the existing environment. temperature, prevailing mean outdoor air ( tpma out ): when used as an input variable in Figure 5-9 for the adaptive model, this temperature is based on the arithmetic average of the mean daily outdoor temperatures over some period of days as permitted in Section 5.4.2.1. temperature, short-wave mean radiant (trsw ): radiant temperature from short-wave direct and diffuse solar radiation expressed as an adjustment to long-wave mean radiant temperature trlw using the calculation procedure in Normative Appendix C of this standard. temperature, standard effective (SET): the temperature of a hypothetical isothermal environment at 50% rh, <0.1 m/s (20 fpm) average air speed Va, and tr = ta, in which the total heat loss from the skin of an imaginary occupant wearing clothing, standardized for the activity concerned, is the same as that from a person in the actual environment with actual clothing and activity level. thermal comfort: that condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation. thermal zone: an area of a building designated by the designer such that the comfort zone is maintained within the occupied zone by local controls for its representative occupant(s).
4. GENERAL REQUIREMENTS
4.1 Where information is required to be identified in this standard, it shall be documented in accordance with and in addition to the requirements in Section 6. 4.2 Identify all of the space types to which the standard is being applied and any locations within a space to which it is not applied. 4.3 For each space type, at least one representative occupant shall be identified. If any known set of occupants is excluded from consideration then these excluded occupants shall be identified. Informative Note: For example, the customers in a restaurant may have a metabolic rate near 1.0 met, while
the servers may have a metabolic rate closer to 2.0 met. Per Section 5.2.1.1, each of these groups of occupants shall be considered separately in determining the conditions required for comfort. In some situations such as this, it will not be possible to provide an acceptable level or the same level of comfort to all disparate groups of occupants. 4.4 For each representative occupant, the metabolic rate M in mets and the insulation Icl in clo shall be determined. 4.5 The thermal environment required for comfort is determined in accordance with Section 5 of this standard.
5. CONDITIONS THAT PROVIDE THERMAL COMFORT
5.1 General Requirements. Section 5 of this standard shall be used to determine the acceptable thermal environment for each representative occupant of a space. Section 5.2 is used to determine representative occupant characteristics.
tpma out
trsw
trlw
tr = ta
Section 5.3 in its entirety or Section 5.4 in its entirety shall be identified as the approach used in determining the acceptable thermal environment. Section 5.3 shall be permitted to be used in any space, and Section 5.4 shall be permitted to be used only in those spaces that meet the applicability criteria in Section 5.4.1. Determine operative temperature to in accordance with Normative Appendix A.
This section covers the determination of the following six factors in steady state. All six factors shall be addressed when defining conditions for acceptable thermal comfort:
a. Metabolic rate b. Clothing insulation c. Air temperature d. Radiant temperature e. Air speed f. Humidity
Informative Notes:
- It is possible for all six of these factors to vary with time. The first two are characteristics of the occupant, and the remaining four are conditions of the thermal environment.
- Average air speed and average air temperature have precise definitions in this standard. See Section 3 for all defined terms.
ANSI/ASHRAE Standard 55-2023 5