Mitsubishi seeks to redefine thermal comfort standard

JAPAN/DENMARK/AUSTRALIA: Mitsubishi Electric has signed agreements with universities in Japan, Denmark and Australia to redefine thermal comfort in buildings and promote it for adoption as an international standard. 

Mitsubishi maintains that there is a growing demand for office environments that support the health, comfort, and productivity of workers, particularly in light of a shrinking working-age population in many countries. It argues that while many factors influence office environments, one of the most significant is thermal conditions, encompassing air temperature, mean radiant temperature, humidity, air velocity, clothing insulation, and metabolic rate. 

Since 2023, Mitsubishi Electric and Waseda University have jointly researched themes such as carbon neutrality and well-being, and initiatives for improving thermal environments. To accelerate this work, they are now launching a collaborative research project with Technical University of Denmark and The University of Sydney, both recognised globally for their expertise in building science and thermal comfort research. 

That agreement has now been extended to include the Technical University of Denmark and the University of Sydney to develop a thermal comfort index that accurately predicts individual thermal sensations. 

The existing standard, the predicted mean vote (PMV), has been widely used to assess thermal environments by calculating people’s expected sensations of heat or cold based on environmental conditions (such as air temperature, mean radiant temperature, relative humidity, and air velocity) and human factors (including clothing insulation and metabolic rate). 

Since its adoption as ISO 7730 in 1984, the PMV has been applied in the design and operation of buildings worldwide. However, Mitsubishi claims that because PMV predictions are based on statistical averages encompassing large numbers of people, it cannot fully capture the individual differences that occur within a typical office population. 

Even when indoor thermal environments are optimised for PMV, Mitsubishi argues, some occupants will inevitably experience discomfort, such as feeling too warm or too cold. 

“In today’s workplaces, where diverse people come together, it is important to move beyond uniform indices like the PMV. Developing a new index that more accurately represents individual thermal sensations is critical to improving well-being for all and creating indoor environments that account for diversity,” the company said in a statement. 

Unlike existing indices, the envisioned index will integrate a wide range of factors, including personal attributes and indoor environmental conditions.