Introduction: What is Thermal Comfort?
In Chapter 1, Sections 1.6.1 and 1.6.2, we introduced the Personal Environmental Model that illustrated the main factors that affect human comfort in an environment. In this chapter, we will focus only on those specific factors that affect thermal comfort.
Thermal comfort is primarily controlled by a building’s heating, ventilating and air-conditioning systems, though the architectural design of the building may also have significant influences on thermal comfort.
This chapter is largely based on ASHRAE’s Standard 55-2004 Thermal Environmental Conditions for Human Occupancy1. In this text, we will abbreviate the title to “Standard 55.” For a much more in-depth discussion of thermal comfort and the way experimental results are presented, see Chapter 8 of the ASHRAE Handbook, 2005, Fundamentals2.
Standard 55 defines thermal comfort as “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation.” There is no way “state of mind” can be measured. As a result, all comfort data are based on researchers asking questions about particular situations, to build a numerical model of comfort conditions. The model is based on answers to questions by many people under many different experimental conditions.
In the next section, we will consider seven factors influencing comfort and then define acceptable thermal comfort conditions.