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AS55 ASHRAE Standard 55: Thermal Environmental Conditions for Occupancy (2017)
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AS55 ASHRAE Standard 55: Thermal Environmental Conditions for Occupancy (2017)

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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 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. For example, during design, a "representative occupant" must be defined, and the air speed and temperature they experience must be an average across the human body at three typical measurement heights. 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.
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