Tag Archives: room temperature

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.


Superconductivity achieved at room temperature for a fraction of a second

Using a pulse of infrared light, physicists at the Max Planck Institute for the Structure and Dynamics of Matter have turned an insulating material into a superconductor even at room temperature, a property that was retained  for only a few millionths of a microsecond. Superconductivity is a state where a material can conduct electricity with absolute zero resistance, with no loss of energy. Traditionally, the state has been demonstrated in metals and ceramics which typically need to be cooled near to absolute zero temperature (-273 degrees Celsius). This breakthrough in fundamental research might spark further interest in achieving the much sought after superconductivity state at room temperature.

Resistance is futile

Star Trek’s Data – ruining jokes since 1987. Via University of Wisconsin.

If you’ve ever touched a high power cable or even a simple appliancea like a hair dryer, you’ve certainly felt how hot it can be. The heating you’re sensing is due to the resistance of material that various wires and electrical components are made of. When electricity passes through these materials, impurities cause electrons to bounce off into atoms, causing them to shift position. This motion is translated into temperature (the vibrations of atoms). Heat is wasted energy (unless you wanted that way for heating) and even power lines that use very good conductors lose roughly 6% of the power they transmit. As such, there are many fields that are interested in using materials that have as little resistance as possible… ideally zero!

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Superconductivity was first discovered by Dutch Physicist Heike Kamerlingh Onnes in 1911, when he and his students found that the electrical resistance of a mercury wire cooled to about 3.6 degrees above absolute zero made a dramatic plunge. The drop was enormous – the resistance became at least twenty thousand times smaller. Since then, much work was made to improve our understanding of this peculiar state. We now know superconductivity is a quantum mechanical phenomenon characterized by the Meissner effect – the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state.

Not all metals can be superconductive. While most metals, like copper or silver, also experience a severe drop in electrical resistance when cooled near to absolute zero, they still show some resistance. While only a couple of materials capable of reaching superconductivity state were identified in 1980, today a whole slew of new alloys have been recognized thanks increase interest in the subject. These include  niobium-titanium, germanium-niobium or niobium nitride. The most promising materials belong to a class based on ceramic materials, like the compound yttrium barium copper oxide (YBCO), which can be superconductive at only minus 200 degrees Celsius.

In effect, superconductivity can be segmented in low temperature conductors and so-called “high temperature” conductors, but even the best of the latter must be cooled below -140 °C to achieve near zero resistance. While we now understand how low temperature conductors like lead work, the same can’t be said about the high temperature ones as many of its mechanisms remain a mystery.

Spooky quantum mechanics

his picture shows a light-induced redistribution of interlayer coupling in YBCO. In the superconducting state, the pump light enhances the superconducting coupling between the copper-oxygen bilayers at the expense of the superconducting coupling within the copper-oxygen bilayers. A similar case is found for the normal state, that the laser light induces a superconducting coupling between the bilayers, meanwhile weakens the precursor superconducting coupling within the bilayers. Credit: Jörg Harms/MPSD,CFEL

his picture shows a light-induced redistribution of interlayer coupling in YBCO. In the superconducting state, the pump light enhances the superconducting coupling between the copper-oxygen bilayers at the expense of the superconducting coupling within the copper-oxygen bilayers. A similar case is found for the normal state, that the laser light induces a superconducting coupling between the bilayers, meanwhile weakens the precursor superconducting coupling within the bilayers. Credit: Jörg Harms/MPSD,CFEL

An important step forward in understanding how these conductors work was made by Max Plank researchers – including Wanzheng Hu, Daniele Nicoletti, Cassi Hunt and Stefan Kaiser lead by Andrea Cavalleri – whose findings might ultimately help materials become superconductive at room temperature.

The team focused their attention on the aforementioned Yttrium barium copper oxide (YBCO), whose crystal structure consists of stacks of two closely spaced copper-oxygen planes, with thicker intermediate layers which contain barium as well as copper and oxygen.  Previous studied showed how pairs of electrons can already hop between the closely-spaced copper oxygen layers at temperature past its critical superconductive temperature of minus 180 degrees Celsius, but not across the large distance to the next bilayer unit. This effect has been likened to a “tunnel”, meaning they can pass through these layers like ghosts can pass through walls.

“Our goal is to use light pulses to stimulate the electron pairs to tunnel freely between all layers at higher temperatures, thus effectively increasing the critical temperature,” explains Hu.

Last year, in 2013, the team reported an amazing discovery. They discovered that when YBCO was irradiated with infrared laser pulses it briefly became superconductive at room temperature. Specifically, oxygen atoms that sit in the gap between pairs of copper-oxygen planes were targeted. The distance between these oxygen atoms and the planes has been found to be directly related to the critical temperature. Don’t jump off your chair, just yet! The superconductive state only survived for a couple of picoseconds (trillionths of a second).


Resonant excitation of oxygen oscillations (blurred) between CuO2 double layers (light blue, Cu yellowy orange, O red) with short light pulses leads to the atoms in the crystal lattice briefly shifting away from their equilibrium positions. Credit: Jörg Harms/MPI for the Structure and Dynamics of Matter

For some time, the scientists were left scratching their heads regarding the specific mechanisms involved. Now, the Max Plank team published a new paper in Nature where they explain what they believe had had happened. To solve the riddle, they enlisted the help of fellow physicists at the LCLS in the US, the world’s most powerful X-ray laser.

“We started by again sending an infrared pulse into the crystal, and this excited certain atoms to oscillate,” explains Max Planck physicist Roman Mankowsky, lead author of the current Nature study. “A short time later, we followed it with a short X-ray pulse in order to measure the precise crystal structure of the excited crystal.”

Besides causing the atoms to oscillate, the infrared pulse shifted their positions in the crystal as well. This briefly caused the copper dioxide double layers thicker – by two picometers or one hundredth of an atomic diameter – while the layer between them was thinned by the same amount. The increments might seem minute, but these were enough to increase the quantum coupling between the double layers to such an extent that the crystal turned superconductive, albeit for a fleeting moment.

Why we need superconductivity

Practical applications that use superconductivity today include  magnets for nuclear spin tomography or particle accelerators. However, if superconductivity can be achieved at lower temperatures, thus reducing the energy required to cool the crystals, then a whole new realm of possibility might unfold before our very eyes – some straight from science fiction like the quantum locked superconducting disk that’s been charming people on the web for some years now. What happens in this particular case is small weak points in a thin superconductor allow magnetic fields to penetrate, locking them in. These are called Flux Tubes.

superconductive quantum locking

Image: YouTube

If the quantum locking effect can maintained with low energy input, we might see things like zero friction rails that seemingly levitate at high speeds. Check out the video below for some mind bending demonstrations.