If women tend to feel colder than men, it's all due to a legacy dating back sixty years.

Setting the air conditioning doesn't always bring everyone into agreement. Choosing the ideal temperature becomes contentious because people have specific and personal needs. But however difficult it may be to draw a clear pattern, there is an obvious gender divide between women and men.

To understand the difference, we need to go back to the 1960s, when Danish engineer Povl Ole Fanger established the thermal comfort model to govern the indoor climate of buildings. Among the factors considered — alongside air speed, humidity, ambient temperature and mean radiant temperature — the engineer took into account the metabolic rate and the thermal insulation provided by clothing. The first factor was calibrated on the values of an average man, the second on the typical attire of the office worker of the era: a man in a jacket, shirt and tie. The issue is that most air-conditioned spaces still set their thermostats according to this standard today.

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A study published in Nature Climate Change found that the average metabolic rate measured in women is approximately 20 to 32 per cent lower than the one used to determine how much to cool offices in summer, because it was calibrated on men's values. The difference lies in the fact that men have, on average, more muscle mass, which generates heat, while women have a higher percentage of body fat, which insulates the internal organs but reduces heat transfer to the skin. The female body has a different thermoregulation strategy: it retains heat internally more effectively, but, having less muscle mass, it ends up triggering vasoconstriction earlier than in men, thereby reducing blood flow to the hands and feet in order to protect the internal organs. Nevertheless, the female thermal response is subject to many variables, including menstruation, pregnancy and menopause.

Air-conditioned indoor spaces (such as offices, schools and shops) are less comfortable for women because they increase the risk of overcooling. Overcooling refers to a condition in which excessive cooling has brought an environment below the recommended comfort temperatures. Beyond the discomfort, this excessive cooling carries other concrete risks. For instance, surfaces cooled below the dew point encourage condensation and, consequently, the proliferation of mould. It is clear that raising thermostats by just a few degrees means ensuring equity — but it also means guaranteeing an ideal temperature for those men who suffer in overly cold environments. And then there is energy, demand for which has increased by an average of around 4 per cent per year since 2000, twice the rate of growth seen for water heating. Consider that today air conditioners and electric fans account for roughly one fifth of the electricity used in buildings worldwide, equivalent to 10 per cent of all global electricity consumption.