ASHRAE 55-2017 PDF: The Ultimate Guide to Thermal Comfort Standards
ASHRAE 55-2017: A Guide to Thermal Comfort Standards
Thermal comfort is a subjective perception of how comfortable a person feels in a given environment. It depends on various factors, such as air temperature, humidity, air movement, clothing, activity level, and personal preferences. Thermal comfort is important for human health, well-being, productivity, and satisfaction in indoor spaces.
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However, achieving thermal comfort for everyone in a building is not an easy task. Different people may have different thermal preferences and expectations, and the indoor environment may change over time due to external weather conditions, internal heat sources, occupancy patterns, and ventilation systems. Therefore, designers, operators, and occupants need some guidance and criteria to ensure acceptable thermal environments for most people in most situations.
That's where ASHRAE 55-2017 comes in. ASHRAE 55-2017 is a standard that specifies the conditions for acceptable thermal environments and provides methods for design, operation, and commissioning of buildings and other occupied spaces. It is developed by ASHRAE, which stands for the American Society of Heating, Refrigerating and Air-Conditioning Engineers, a professional organization that sets standards and guidelines for the HVAC industry.
In this article, we will explain what ASHRAE 55-2017 is and why it is important, how to use it for thermal comfort design and assessment, and where to find more information and resources on this topic.
What is ASHRAE 55-2017 and why is it important?
The scope and purpose of ASHRAE 55-2017
ASHRAE 55-2017 applies to indoor spaces that are intended for human occupancy for at least 15 minutes. It does not apply to outdoor spaces or spaces that are designed for special purposes, such as cold storage rooms, operating rooms, or hot yoga studios.
The purpose of ASHRAE 55-2017 is to define the range of indoor thermal environmental conditions that are acceptable for most occupants. Acceptable means that at least 80% of the occupants would not express dissatisfaction with the thermal environment. Dissatisfaction means that the occupants would prefer a warmer or cooler environment than the current one.
ASHRAE 55-2017 also provides methods for evaluating the thermal environment based on measurements or calculations of environmental variables (such as air temperature, humidity, air speed, and radiant temperature) and personal variables (such as clothing insulation and metabolic rate). These methods can be used to design, operate, and commission buildings and other occupied spaces to achieve acceptable thermal comfort conditions.
The benefits of complying with ASHRAE 55-2017
Complying with ASHRAE 55-2017 can bring many benefits for building owners, managers, designers, operators, occupants, and society at large. Some of these benefits are:
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Improved occupant health, well-being, productivity, and satisfaction. Thermal comfort can affect physical and mental health, mood, alertness, concentration, performance, and satisfaction of occupants. By providing acceptable thermal environments, ASHRAE 55-2017 can help prevent or reduce thermal stress, discomfort, fatigue, irritation, illness, absenteeism, turnover, and complaints.
Reduced energy consumption and greenhouse gas emissions. Thermal comfort can also affect energy use and environmental impact. Thermal comfort can influence the demand for heating, cooling, ventilation, and lighting in buildings. By following ASHRAE 55-2017, building designers and operators can optimize the energy efficiency and performance of HVAC systems and reduce the carbon footprint of buildings.
Enhanced compliance with codes, standards, and regulations. Thermal comfort is often a requirement or a criterion in various codes, standards, and regulations that govern the design, construction, operation, and maintenance of buildings and other occupied spaces. By adhering to ASHRAE 55-2017, building owners and managers can demonstrate compliance with these codes, standards, and regulations and avoid potential penalties or litigation.
How to use ASHRAE 55-2017 for thermal comfort design and assessment?
The analytical method and the elevated airspeed method
The analytical method is the main method for thermal comfort design and assessment in ASHRAE 55-2017. It is based on the heat balance model of the human body and the psychrometric chart. It defines the acceptable range of operative temperature (the average of air temperature and mean radiant temperature) for a given combination of clothing insulation, metabolic rate, air speed, and humidity. The acceptable range is represented by a comfort zone on the psychrometric chart.
The analytical method can be applied to mechanically conditioned spaces (with or without local control) or mixed-mode spaces (with both mechanical and natural ventilation). It can also be used to evaluate the effect of elevated airspeed on thermal comfort. The elevated airspeed method allows for higher operative temperatures in spaces where the occupants have access to personal control of air movement, such as fans or operable windows. The elevated airspeed method can increase the upper limit of the comfort zone by up to 3C depending on the air speed and the turbulence intensity.
The adaptive method for naturally conditioned spaces
The adaptive method is an alternative method for thermal comfort design and assessment in ASHRAE 55-2017. It is based on the adaptive model of thermal comfort, which assumes that occupants can adapt to their thermal environment through behavioral adjustments, such as changing clothing, opening windows, or using fans. It defines the acceptable range of operative temperature as a function of the running mean outdoor air temperature (the average of the daily mean outdoor air temperatures over the previous 7 to 30 days).
The adaptive method can only be applied to naturally conditioned spaces (without mechanical cooling or heating) or mixed-mode spaces (with both mechanical and natural ventilation) when the mechanical system is not operating. It can also be used to evaluate the effect of occupant expectations on thermal comfort. The adaptive method allows for different comfort zones for different types of buildings, such as residential, office, or educational buildings.
The draft risk method for the ankle region
The draft risk method is a supplementary method for thermal comfort design and assessment in ASHRAE 55-2017. It is based on the draft sensation model, which predicts the percentage of occupants who would feel drafty in a given environment. It defines the acceptable range of air speed and temperature for the ankle region (the area between 0.1 m and 0.6 m above the floor) where occupants are more sensitive to draft.
The draft risk method can be applied to any type of space where occupants are seated or standing. It can also be used to evaluate the effect of floor heating or cooling systems on thermal comfort. The draft risk method limits the maximum air speed in the ankle region to 0.15 m/s for warm environments (above 23C) and 0.10 m/s for cool environments (below 23C).
Where to find more information and resources on ASHRAE 55-2017?
The ASHRAE website and the ASHRAE Thermal Comfort Tool
The ASHRAE website is the official source of information and resources on ASHRAE 55-2017. You can find the full text of the standard, as well as errata, interpretations, addenda, and updates on . You can also purchase a hard copy or a digital version of the standard from the ASHRAE bookstore.
The ASHRAE Thermal Comfort Tool is a software application that can help you apply ASHRAE 55-2017 methods for thermal comfort design and assessment. You can use it to calculate environmental variables, personal variables, comfort zones, draft risk, PMV/PPD indices, adaptive comfort models, and more. You can also use it to generate graphs, tables, reports, and charts based on your input data. You can download the ASHRAE Thermal Comfort Tool from .
The ASHRAE publications and courses on thermal comfort
The ASHRAE publications and courses are another source of information and resources on ASHRAE 55-2017. You can find various books, journals, magazines, newsletters, and papers that cover the topics of thermal comfort, indoor environmental quality, HVAC systems, and building design and operation. So