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ASHRAE Standard 55-2020 -- Thermal Environmental Conditions for Human Occupancy (ANSI Approved), 2021
- ANSI/ASHRAE Standard 55-2020 [Go to Page]
- CONTENTS
- FOREWORD
- 1. PURPOSE
- 2. SCOPE [Go to Page]
- 2.1 The environmental factors addressed in this standard are temperature, thermal radiation, humidity, and air speed; the personal factors are those of activity and clothing.
- 2.2 It is intended that all of the criteria in this standard be applied together, as comfort in the indoor environment is complex and responds to the interaction of all of the factors that are addressed herein.
- 2.3 This standard specifies thermal environmental conditions acceptable for healthy adults at atmospheric pressure equivalent to altitudes up to 3000 m (10,000 ft) in indoor spaces designed for human occupancy for periods not less than 15 minutes.
- 2.4 This standard does not address such nonthermal environmental factors as air quality, acoustics, illumination, or other physical, chemical, or biological space contaminants that may affect comfort or health.
- 2.5 This standard shall not be used to override any safety, health, or critical process requirements.
- 3. DEFINITIONS
- 4. GENERAL REQUIREMENTS [Go to Page]
- 4.1 Where information is required to be identified in this standard, it shall be documented in accordance with and in addition to the requirements in Section 6.
- 4.2 Identify all of the space types to which the standard is being applied and any locations within a space to which it is not applied.
- 4.3 For each space type, at least one representative occupant shall be identified. If any known set of occupants is excluded from consideration then these excluded occupants shall be identified.
- 4.4 For each representative occupant, the metabolic rate M in mets and the insulation I in clo shall be determined.
- 4.5 The thermal environment required for comfort is determined in accordance with Section 5 of this standard.
- 5. CONDITIONS THAT PROVIDE THERMAL COMFORT [Go to Page]
- 5.1 General Requirements. Section 5 of this standard shall be used to determine the acceptable thermal environment for each representative occupant of a space. Section 5.2 is used to determine representative occupant characteristics.
- 5.2 Method for Determining Occupant Characteristics
- 5.3 Method for Determining Acceptable Thermal Environment in Occupied Spaces. Section 5.3 is permitted to be used to determine the requirements for thermal comfort in all occupied spaces within the scope of this standard.
- 5.4 Determining Acceptable Thermal Conditions in Occupant-Controlled Naturally Conditioned Spaces (Adaptive Model)
- 6. DESIGN COMPLIANCE [Go to Page]
- 6.1 Design. Building systems (i.e., combinations of mechanical systems, control systems, and thermal enclosures) shall be designed so that at outdoor and indoor design conditions they are able to maintain the occupied space or spaces at indoor therma...
- 6.2 Documentation. The method and design conditions appropriate for the intended use of the building shall be selected and documented as follows. (Informative Note: Some of the requirements in items (a) through (h) below are not applicable to natural...
- 7. EVALUATION OF COMFORT IN EXISTING BUILDINGS [Go to Page]
- 7.1 Introduction. Evaluation of comfort in existing buildings is not a requirement of this standard. When such evaluation is otherwise required (e.g., by code or another standard) use one of the following methods:
- 7.2 Criteria for Comfort in Existing Buildings
- 7.3 Measurement Methods
- 7.4 Evaluation Methods
- 8. REFERENCES
- NORMATIVE APPENDIX A: METHODS FOR DETERMINING OPERATIVE TEMPERATURE
- NORMATIVE APPENDIX B: COMPUTER PROGRAM FOR CALCULATION OF PMV-PPD
- NORMATIVE APPENDIX C: PROCEDURE FOR CALCULATING COMFORT IMPACT OF SOLAR GAIN ON OCCUPANTS [Go to Page]
- C1. CALCULATION PROCEDURE
- C2. INPUTS TO CALCULATION PROCEDURE
- C3. COMPUTER PROGRAM FOR CALCULATING COMFORT IMPACT OF SOLAR GAIN ON OCCUPANTS
- C4. COMPUTER CODE VALIDATION TABLE
- NORMATIVE APPENDIX D PROCEDURE FOR EVALUATING COOLING EFFECT OF ELEVATED AIR SPEED USING SET [Go to Page]
- D1. Calculation Overview
- D2. CALCULATION PROCEDURE
- D3. Validation Table for SET Calculation
- D4. Computer Program for Calculation of Set
- INFORMATIVE APPENDIX E: CONDITIONS THAT PROVIDE THERMAL COMFORT [Go to Page]
- E1. Introduction
- E2. Thermal Comfort Factors
- E3. Variation among Occupants
- E4. Temporal Variation
- E5. Local Thermal Discomfort
- E6. Variation in Activity Level
- E7. Naturally Conditioned Spaces
- INFORMATIVE APPENDIX F: USE OF METABOLIC RATE DATA
- INFORMATIVE APPENDIX G: CLOTHING INSULATION
- INFORMATIVE APPENDIX H: COMFORT ZONE METHODS [Go to Page]
- H1. Determining Acceptable Thermal Conditions in Occupied Spaces
- H2. ANALYTICAL COMFORT ZONE METHOD
- H3. ELEVATED AIR-SPEED COMFORT ZONE METHOD
- H4. Humidity Limits
- INFORMATIVE APPENDIX I: LOCAL DISCOMFORT AND VARIATIONS WITH TIME [Go to Page]
- I1. Local Thermal Discomfort
- I2. Radiant Temperature Asymmetry
- I3. Draft
- I4. Vertical Air Temperature Difference
- I5. Floor Surface Temperature
- I6. Temperature Variations with Time
- I7. Cyclic Variations
- I8. Drifts or Ramps
- INFORMATIVE APPENDIX J: OCCUPANT-CONTROLLED NATURALLY CONDITIONED SPACES
- INFORMATIVE APPENDIX K: SAMPLE DESIGN COMPLIANCE DOCUMENTATION
- INFORMATIVE APPENDIX L: MEASUREMENTS, SURVEYS, AND EVALUATION OF COMFORT IN EXISTING SPACES: PARTS 1 AND 2 [Go to Page]
- L1. PHYSICAL MEASUREMENTS [Go to Page]
- L1.1 Overview of Comfort Prediction Using Physical Measurements. Measurements of indoor environmental parameters are converted to predictions of occupants’ thermal satisfaction through calculations and tests against comfort limits.
- L1.2 Environmental and Occupant Measurements. Environmental parameters are described in Section 5.1, and their measurement requirements are described in Section 7.3. For nonsteady conditions, the Section 7.3.3 prescribes measurement timing.
- L2. SURVEYING OCCUPANTS [Go to Page]
- L2.1 Point-in-time (“right-now”) surveys are used to evaluate thermal sensations of occupants at a single point in time. Thermal comfort researchers have used these surveys to correlate thermal comfort with environmental factors such as those inc...
- L2.2 A second form of thermal environment survey, a satisfaction survey, is used to evaluate thermal comfort response of the building occupants in a certain span of time. Instead of evaluating thermal sensations and environmental variables indirectly...
- L3. Evaluation of Comfort in Existing Spaces [Go to Page]
- L3.1 Analysis Based on Occupant Surveys. Surveys can assess comfort directly, in contrast to the indirect approach of calculating comfort through comfort models using measured environmental variables.
- L3.2 Analysis Based on Measurements of Environmental Variables. Environmental measurements are linked to occupant comfort through comfort models. Two comfort models, PMV and adaptive, are specific to mechanically conditioned and naturally ventilated ...
- INFORMATIVE APPENDIX M: INFORMATIVE REFERENCES AND BIBLIOGRAPHY
- INFORMATIVE APPENDIX N: ADDENDA DESCRIPTION [Go to Page]
