The Heat of the Matter Behind Design for Thermal Comfort

by Amarpreet Sethi

In this installment of our series on high-performance design features, we’re exploring the effects viewsdaylighting, thermal comfort, and indoor air quality have in producing significantly positive impacts on workplace productivity. Though we are exploring each feature individually in these installments, we consider these design features holistically in our high-performance design practice for workplace, which focuses on complementary evidence-based design strategies to improve the health and wellness of users. And as part of an integrated strategy, thermal comfort is a multi-faceted feature that profoundly affects user contentment with the built environment.

How do we define thermal comfort? According to ASHRAE Standard 55, it is the state of mind that is satisfied with the thermal environment, and is assessed by subjective evaluation. Factors that affect thermal comfort include clothing, metabolic activity, indoor air temperature, humidity, radiant temperature, and air speed. In addition to these conditions, acceptable thermal conditions can also shift if the space is naturally conditioned with user-controlled operable windows. This shift or method is also called the adaptive thermal comfort model that relates acceptable indoor temperature ranges to outdoor climate parameters. 

A user’s temperature perception is based on heat exchange with the immediate environment through convective and radiant heat exchange. This is why someone working close to a window with sun beating down on him or her may feel warmer in the summer and colder in the winter months, even though the air temperature consistently remains at a comfortable 72°– 75° Fahrenheit.

How Much Does Thermal Comfort Matter?
Thermal comfort is a topic of discussion in offices everywhere you go. From the Washington Post to the BBC to the Wall Street Journal, potentially contributing factors such as age, gender, and clothing choices have been explored. As architects and engineers of the workplace, we use evidence-based design tactics to enhance thermal comfort in spaces. Here are some of the most informative studies on the topic.

A 2007 study by Tanabe, Haneda, and Nishihara found a group of call center workers and a group of college students had differing levels of performance during simulated office tasks – such as typing, reacting to choices, and doing math – depending on the temperature in which they worked.1 One part of the study determined that higher temperatures – at or above 33° Celsius, or 91° Fahrenheit – decreased oxygenated blood supply. It is at these same temperature levels that participants experienced a decline in performance, and complained of fatigue and discomfort.