Thermal Environmental Conditions for Human Occupancy
ASHRAE Standing Standard Project Committee 55

This project committee is responsible for maintaining ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy (ANSI Approved)

This standard specifies the combinations of indoor space environment and personal factors that will produce thermal environmental conditions acceptable to 80% or more of the occupants within a space. The environmental factors addressed are temperature, thermal radiation, humidity, and air speed; the personal factors are those of activity and clothing.

ANSI/ASHRAE Standard 55-2017 is the latest edition of Standard 55.

The 2017 edition of ANSI/ASHRAE Standard 55 incorporates seven published addenda to the 2013 edition, and provides three compliance methods:

• a graphic method for simple situations,
• an analytical method for more general cases, and
• a method that uses elevated air speed to provide comfort.

The standard has a separate method for determining acceptable thermal conditions in occupant-controlled naturally conditioned spaces. Given the widespread and easy accessibility of computing power and third-party implementations of the analytical method, it is expected that more users will favor the comprehensive analytical methods over the graphical method.

Since 2013, Standard 55 has been rewritten with a renewed focus on application of the standard by practitioners and use of clear, enforceable language. Requirements are now clearly stated and calculation procedures appear sequentially. All informative background information has been moved to informative appendices.

Other noteworthy additions to the standard include clarification of the three comfort calculation approaches in the elevated air speed section; simplification of Appendix A to a single procedure for calculating operative temperature; an update to the scope to ensure the standard isn’t used to override health, safety, and critical process requirements; a new requirement for calculating change to thermal comfort resulting from direct solar radiation; and removal of permissive language throughout the standard.

Documentation requirements to show that a design complies with Standard 55 are contained in Section 6, and a sample compliance form is provided in Appendix K. Both of these sections are clarified and streamlined for use by owners and third-party rating systems.

Standard 55 was first published in 1966 and republished in 1974, 1981, and 1992. Beginning in 2004, it is now updated on a regular basis using ASHRAE’s continuous maintenance procedures. According to these procedures, Standard 55 is continuously revised by addenda that are publicly reviewed, approved by ASHRAE and ANSI, and published and posted for free on the ASHRAE Web site.

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• To download the latest published addenda to ASHRAE Standards  Click Here