ASHRAE Standard 55 specifies conditions for acceptable thermal environments and is intended for use in design, operation, and commissioning of buildings and other occupied spaces.

The 2023 edition of ANSI/ASHRAE Standard 55 incorporates eleven published addenda to the 2020 edition. This edition includes a new method for the assessment of local thermal discomfort with vertical air temperature gradient between the head level and ankle level. The standard now has wider applicability, covering metabolic rates up to 4 from 2. Calculation methods have been consolidated and simplified to two methods, standard and adaptive, and a new flowchart provides guidance on when to use each calculation method. Finally, documentation requirements in the standard have been overhauled with additions, clarifications, and simplifications, along with a new example spreadsheet compliance form to replace the previous form.