Which is more important, keeping HVAC costs low or building occupants happy? Rather, which is easier? Is there a happy medium that can be achieved?
Keeping building occupants comfortable while minimizing energy use is a balancing act for engineers who design HVAC&R systems and buildings. One way they can achieve this balance is through requirements in a standard from an international technical association.
ASHRAE’s Standard 55, Thermal Environmental Conditions for Human Occupancy, specifies the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space. Earlier this week, research that looks at the method used to determine thermal comfort in Standard 55 was published via an article, “Energy Consumption in Buildings and Female Thermal Demand,” in Nature Climate Change. The research looks at the method used to determine thermal comfort in ANSI/ASHRAE Standard 55.
“The interpretation of the authors regarding the basis for Standard 55 is not correct,” Bjarne Olesen, Ph.D., a member of the ASHRAE Board of Directors, internationally renowned thermal comfort research and former chair of the Standard 55 committee, said. “The part of the standard they are referring to is the use of the PMV/PPD index. This method is taken from an ISO/EN standard 7730, which has existed since 1982. The basic research for establishing comfort criteria for the indoor environment was made with more than 1,000 subjects with equal amount of women and men.
“In the main studies, where they did the same sedentary work and wore the same type of clothing, there were no differences between the preferred temperature for men and women. So the researchers’ finding of a lower metabolic rate for females will not influence the recommended temperatures in the existing standards. Also their study is not conclusive. They only studied 16 females at a sedentary activity.
They should also have studied 16 men at the same activity to be able to compare. The reason why we, in some field studies, find that women prefer higher room temperature than men is attributed to the level of clothing. Women adapt better their clothing to summer conditions while men are still wearing suit and tie. So if the thermostat is set to satisfy the men, the women will complain about being too cold. In the standard, this adaption of clothing to summer is taken into account so if the standard is followed the women would be satisfied; but maybe not the men.”