Not too hot, not too cold. What’s the ideal room temperature?

Either at home or at the office, you’ve probably struggled more than once to get the room temperature to your exact preferred level. But that ideal temperature actually depends on many factors such as your age and sex, the time of the year and the exact room in which you are located.

Credit Flickr Jernej Furman (CC BY 2.0)

Room temperature… but what’s the room?

According to the American Heritage Dictionary, room temperature is defined as “around 20–22 °C (68–72 °F)”, while the Oxford English Dictionary defines the temperature as “about 20 °C (68 °F)”. However, what we understand as room temperature is actually a range of temperatures, chosen to represent comfortable habitation for humans. There is no one fixed room temperature.

At the room temperature range, a person isn’t either hot or cold when wearing ordinary indoor clothing, and while that sounds trivial, it’s actually quite important. The average body temperature for a human is 37ºC (98.6 Fahrenheit) and our brains work hard to make sure our bodies maintain this temperature. To do this, our brain makes our body burn glucose to warm up or ventilate and sweat to cool down. See, your brain is both wise and selfish — it knows what’s best for itself is best for the body.

Throughout different cultures, room temperature can vary quite significantly, both in the same period, and seasonally (what is considered ‘room temperature’ in the summer might not coincide with the winter room temperature).

The World Health Organization (WHO) suggests a minimum of 18ºC (64.4) as the ideal home temperature for healthy and appropriately-dressed individuals, meaning no vest tops or shorts on indoors during winter. Meanwhile, for those very old or very young or with an illness, the WHO suggests a 20ºC (68 Fahrenheit) temperature.

The range between 18–24º C (64–75 Fahrenheit) isn’t associated with health risks for healthy adults with appropriate clothing, humidity and other factors, the WHO argues. In other words, anywhere within this range, you should be alright. Cold air inflames lungs and inhibits circulation, increasing the risk of respiratory conditions

However, temperatures lower than 16 °C (61 Fahrenheit) with humidity above 65% were associated with respiratory hazards including allergies. Unfortunately, income constraints also direct what’s an acceptable room temperature. Lack of energy affordability can make it difficult for people on low incomes to heat their houses adequately. Even temperatures lower than 16 °C have been linked with worse health outcomes.

Best temperatures at home

A pleasant temperature is important for our homes.

‘Room temperature’ also depends on the room — it’s not the same whether you are in the living room, the bedroom, or the bathroom when choosing your ideal temperature.

The French Environment & Energy Management Agency (ADEME) came up with a few useful guidelines to follow depending on the room we are at. For living areas such as the living room or the dining room, ADEME suggests an ideal temperature of 19ºC, considering it’s a place where we spend a lot of inactive time such as working or watching TV. This varies according to our age and health. Older people should have a temperature between 20-22ºC (68-71 Fahrenheit).

The situation changes in the bedroom, as an excessive temperature may affect our sleep. ADEME recommends a temperature that doesn’t exceed 17ºC (62.6 Fahrenheit), which can be lowered to 16ºC (60.8 Fahrenheit) with a good duvet and a well-isolated room. This can also be complemented with a hot-water bottle. As a rule of thumb, the bedroom can be 1-2 degrees colder than the rest of the house.

The bathroom is also a quite unique place in the house. It’s unused most of the day but we want it to be at the right temperature when we do use it. Going into a bathroom when it’s too warm or too cold can be annoying or even dangerous for your health (especially if it’s cold after you take a bath). That’s why ADEME recommends a temperature of 22ºC (71 Fahrenheit), which would be enough to feel good after we get out of the shower or the bath.

What about work?

Work is a whole different issue, and who hasn’t argued about the thermostat or air conditioning with a coworker? Finding an ideal office temperature to please everyone is not only hard — is basically impossible, several studies have found

Unsurprisingly, most people are discontent with their work temperature. A survey in 2015 to office workers in the US found that 50% were dissatisfied at least several times a month with the temperature of their office. And that’s not it, as 42% said their offices were too warm during summer and 56% considered them too cold during winter — and this has many implications for organizations and their workers.

Not being able to keep workers comfortable has significant financial implications. In the UK, a study showed as much as 2% of the office hours are wasted by people arguing over the temperature levels, which cost the economy $15 billion per year. Meanwhile, a study in Australia showed temperature arguments cost $6.2 billion per year. Even with all the arguments, we still have trouble finding the best room temperature.

The effects on productivity are also quite clear. A study tracked the activity of clerks in an insurance office to measure the impact of temperature in their efficiency. With a 25ºC (77 Fahrenheit) temperature workers typed non-stop with an error rate of 10%. When the temperature dropped five degrees, they were half as productive. Even more surprisingly, the temperature in the room can influence people’s willingness to collaborate. A study showed that warmer conditions induced greater social proximity and the use of more concrete language, while another study found that holding a cup of hot coffee encouraged workers to judge others are more generous and caring.

Men vs women

There’s even a gender bias in thermal comfort, a study has found. Most office buildings set temperatures based on a decades-old formula that uses the metabolic rates of men to calculate the ideal room temperature… but this doesn’t really work for women. Women, on average, prefer room temperatures several degrees warmer than men. This not only means women are colder but also lowers their ability to perform certain tasks in the office at a temperature that’s more comfortable for men (the opposite can also be true).

Study author Agne Kajackaite worked with over 500 German college students, placing them in a room and taking tests at different temperatures, ranging from 16ºC (61 Fahrenheit) to 32ºC (92 Fahrenheit). The researchers found a difference in performance between men and women depending on the temperature.

Previous studies showed women preferred rooms at 25ºC (77 Fahrenheit), while men are more comfortable at (21.6ºC). Women are usually colder than men at the same temperature because of the physiology. Nevertheless, before Kajackaite’s work, the consequences of being colder weren’t much clear. The warmer the room, the better the women performed.

“As the temp went up, women did better on math and verbal tasks, and men did worse. And the increase for women in math and verbal tasks was much larger and more pronounced than the decrease in performance of men,” Tom Chang, co-author, said in a statement.

A matter of health

While for many healthy and young individuals the right indoor temperature might be a matter of comfort and productivity, for the elderly it’s also a matter of health. During summer, seniors are exposed to an increased risk, while in winter the risks can be as just as severe.

A study found it only takes 45 minutes for a cold room to have a significant impact on the elderly, decreasing the strength in most of the major muscle groups. With a reduced strength, their safety and independence can be affected. With that in mind, the study suggested a minimum temperature of 18ºC (65 Fahrenheit).

This is also very important for babies’ health, with a recommended room temperature between 20ºC to 22ºC (68 to 72 Fahrenheit). This reduces the risk of overheating, which has been linked to fatal sleep accidents and sudden infant death syndrome (SIDS). As a general rule, if the bedroom temperature is comfortable for you, it’s also for your baby.

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