ANSI ASHRAE Standard 55-2020 PDF

Full title and description

ANSI/ASHRAE Standard 55-2020 — Thermal Environmental Conditions for Human Occupancy. Specifies combinations of environmental (air temperature, radiant temperature, humidity, air speed) and personal factors (activity and clothing) that produce acceptable thermal environments for a majority of occupants; intended for use in the design, operation, evaluation and commissioning of buildings and other occupied spaces.

Abstract

This edition (the 2020 version) incorporates multiple addenda to the 2017 standard and emphasizes analytical methods (including an elevated-airspeed method) and an adaptive model for occupant-controlled naturally conditioned spaces. New material in this edition includes procedures for assessing local thermal discomfort (for example vertical temperature gradients and draft risk at ankle level) and the introduction of Thermal Environmental Control Classification levels for documenting occupant control.

General information

• Status: Historical / superseded by ANSI/ASHRAE Standard 55-2023 (the 2020 edition is a prior published version).
• Publication date: 2020 (published/issued as the 2020 edition; some listings cite early 2021 for distribution metadata).
• Publisher: American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); ANSI-approved.
• ICS / categories: Building installations / indoor environment; commonly cataloged under installations in buildings (ICS 91.140) and indoor environmental quality categories.
• Edition / version: ANSI/ASHRAE Standard 55-2020 (edition year 2020).
• Number of pages: Source-dependent (commonly listed between ~75–80 pages depending on format and front matter); catalog entries list ~75–76 pages while some distributors list 80 pages.

Scope

Addresses the four primary environmental factors that affect thermal comfort—air temperature, thermal radiation, humidity and air speed—and the two primary personal factors—activity (metabolic rate) and clothing insulation. The standard applies to occupied indoor spaces (typical metabolic and clothing ranges are specified), provides methods to determine conditions that will be acceptable to a significant proportion of occupants, and gives procedures for demonstrating compliance in design and for evaluating comfort in existing buildings. It does not address nonthermal factors such as air quality, acoustics or illumination.

Key topics and requirements

• Analytical thermal comfort method (PMV/PPD based) and companion elevated-airspeed method for extended applicability.
• Adaptive model for occupant-controlled naturally conditioned spaces, with expanded applicability.
• Criteria and procedures for acceptable ranges of operative temperature, humidity and air speed, and for combining environmental and personal factors.
• New provisions (in the 2020 edition) for local thermal discomfort assessment (e.g., vertical air temperature gradient, ankle-region draft risk).
• Thermal Environmental Control Classification levels for documenting occupant control and compliance documentation requirements.
• Calculation algorithms and example forms/spreadsheets for design compliance and evaluation.

Typical use and users

Used by HVAC designers and engineers, building commissioning agents, facility managers, architects, researchers in indoor environmental quality, code officials and consultants who need to specify or evaluate thermal comfort conditions in commercial, institutional and many residential building types. It is referenced by building standards, energy codes and other ASHRAE standards where thermal comfort criteria are required.

Related standards

Commonly referenced alongside other ASHRAE standards and building codes, including ANSI/ASHRAE Standard 62.1 (Ventilation and Acceptable Indoor Air Quality), ANSI/ASHRAE Standard 62.2 (Residential IAQ), and energy standards such as ANSI/ASHRAE/IES Standard 90.1. Earlier and later editions of the same standard (55-2017; superseding 55-2023) and published addenda to 55-2020 are also relevant for compliance history.

Keywords

thermal comfort, PMV, PPD, operative temperature, adaptive thermal comfort, indoor environmental quality (IEQ), HVAC design, draft, thermal neutrality, ASHRAE 55, Thermal Environmental Control Classification.

FAQ

Q: What is this standard?

A: ANSI/ASHRAE Standard 55-2020 specifies acceptable thermal environmental conditions for human occupancy and provides methods for determining and documenting thermal comfort in buildings and occupied spaces.

Q: What does it cover?

A: It covers environmental factors (air temperature, radiant temperature, humidity, air speed) and personal factors (activity/metabolic rate and clothing) and gives analytical and adaptive methods, local discomfort assessments, and compliance documentation procedures.

Q: Who typically uses it?

A: HVAC and building design professionals, commissioning agents, facility managers, researchers, consultants and code officials who need to design for or evaluate occupant thermal comfort.

Q: Is it current or superseded?

A: The 2020 edition is a published historical edition that has been revised by ANSI/ASHRAE Standard 55-2023; users should confirm whether their project or regulatory reference requires the 2020 text or the later 2023 edition.

Q: Is it part of a series?

A: Yes — Standard 55 is a recurring ASHRAE standard (previous editions include 2017, 2013, 2010, etc.) maintained on continuous maintenance with published addenda; it is typically used alongside related ASHRAE standards on ventilation, IAQ and energy.

Q: What are the key keywords?

A: thermal comfort, PMV/PPD, adaptive model, operative temperature, indoor environment, HVAC, occupant control.