ASHRAE-Standard-55 - Page 026
Extracted Content
7.4.2 Evaluation Based on Physical Measurements of the Thermal Environment. Use one of the following approaches in Section 7.4.2.1 or 7.4.2.2.
7.4.2.1 Approaches to Predicting whether a Thermal Environment is Satisfactory at a Specific Instance in Time
a. Mechanically conditioned buildings:
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Occupied spaces shall be evaluated using the PMV comfort zone as defined in Section 5.3.
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Local thermal discomfort shall be evaluated using the limits to environmental asymmetry prescribed in Section 5.3.5. b. Buildings with occupant-controlled operable windows:
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Occupied spaces shall be evaluated using the indoor operative temperature to contours of the adaptive model comfort zone in Section 5.4, including the contour extensions for average air speeds Va above 0.3 m/s (59 fpm). 7.4.2.2 Approaches to Predicting whether a Thermal Environment is Satisfactory over Time. Section 7.4.2.2.1 shall be used to quantify the number of hours in which environmental conditions are outside the comfort zone requirements during occupied hours in the time period of interest. Exceedance is measured by exceedance hours (EH) ( Informative Note: See definition in Section 3). Section 7.4.2.2.2 is permitted but not required to be used with Section 7.4.2.2.1.
7.4.2.2.1 EH is calculated for the PMV comfort zone and adaptive model comfort zone as follows:
a. Letting each sum be over occupied hours within the specified period, and comfort indices respective to
that hour, for PMV comfort zone, EH = Hdisc, where Hdisc is a discomfort hour; Hdisc = 1 if | PMV | – 0.5
- 0 and 0 otherwise. b. For adaptive model comfort zone, where H>upper and H<lower are discomfort hours outside of comfort
zone boundaries tupper and tlower, EH = ( H>upper + H<lower ), where H>upper = 1 if top - tupper and 0 otherwise, and H<lower = 1 if top < tlower and 0 otherwise. c. Units are in hours. Exceedance hours can also be expressed as a probability by dividing EH by total
occupied hours.
7.4.2.2.2 It is permissible to quantify the expected number of episodes of discomfort, rate-of-change exceedances, and local discomfort exceedances, within a time period of interest.
8. REFERENCES
- ASHRAE. 2021. ASHRAE Handbook—Fundamentals. Peachtree Corners, GA: ASHRAE.
- ASHRAE. 2022. ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings. Peachtree Corners, GA: ASHRAE.
- Tartarini, F., S. Schiavon, T. Cheung, and T. Hoyt. 2020. CBE Thermal Comfort Tool: Online Tool for Thermal Comfort Calculations and Visualizations. SoftwareX 12 (July 2020):100563. https://doi.org/ 10.1016/j.softx.2020.100563.
- Blum, H.F. 1945. Solar heat load, its relationship to the total heat load, and its relative importance in the design of clothing. Journal of Clinical Investigation 24:712–21.
- ASHRAE. 2022. ANSI/ASHRAE Standard 62.1, Ventilation and Acceptable Indoor Air Quality . Peachtree Corners, GA: ASHRAE.
- ASHRAE. 2022. ANSI/ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Resi- dential Buildings . Peachtree Corners, GA: ASHRAE.
24 ANSI/ASHRAE Standard 55-2023