What is the ideal room temperature for sleep? Like Goldilocks tasting the three bears’ porridge, your room temperature should be not too hot, not too cold, but “just right”. How is that for helpful guidance? For you, “just right” might be on the cool side, while your romantic bed partner might prefer a Caribbean vacation-type sleep environment with a warmer room and fan gently blowing over the bed mimicking an evening ocean breeze. Room temperature really is a matter of preference, up to a certain point.
For most people, a slightly cooler room results in better sleep quality. This is, in part at least, because your core body temperature cools down a little during sleep. A warmer room counteracts your body’s natural thermoregulatory rhythm and does not allow your core body temperature to drop as easily. This can significantly disrupt your sleep quality and leave you feeling fatigued even after eight hours of sleep. A cooler room temperature matches what your brain and body is looking for during sleep, a cool down. But you can’t go too cold either. If the room is uncomfortably cold, sleep quality will also be disrupted and increase the risk of fatigue the next day.
What is the “certain point” where room temperature preference can be used to guide where you set your thermostat? It seems that, if ambient humidity is between 40% and 60%, then ambient room temperatures between 17°c and 28°c won’t disrupt sleep. This means that if you like it warmer, you can crank up the heat and if you like it cooler you can drop it, just keep the humidity in mind.
There is one complicating factor. Your PJ’s, mattress and bedding can impact temperature and humidity. They need to either wick away the heat and humidity or retain it so that your brain and body experience your preferred temperature. In other words, a room that is 26°c could disrupt your sleep even if you like it warm if your mattress, bedding and PJ’s do not wick away heat and humidity and a room that is 17°c will disrupt your sleep even if you like it cool if your mattress, bedding and PJ’s don’t retain heat.
Understanding the role of your PJ’s, mattress and bedding on temperature, humidity and sleep quality can bring a little harmony back into the bedrooms of romantic partners with different “ideas” of where the thermostat should be set for a good slumber. If your preferred temperatures are different, you can either bundle up in cozy PJ’s or strip down to your birthday suit.
OK, so now we have some useable guidance for our home sleep environments. But stripping down in a work nap room might not be appropriate and sometimes it is difficult to provide efficient temperature control for individual rooms in bunkhouses and other company provided sleep facilities. For these situations, the best advice is to err on the side of caution and to try to design sleep facilities with constant ambient temperatures that are a little cooler and between 17°c and 22°c with slightly higher humidities that are between 30% & 50%. Lower humidities can dry out the respiratory system, make it a little difficult to breath and disrupt sleep. Humidities higher than 50% can be too uncomfortable and can make ideal 17°c to 22°c temperatures feel very different. But remember comfort is key and that allowing your sleepers to adjust their bedding so they can get closer to their preferred temperatures is necessary. Discomfort of any sort, including feeling too hot or cold while sleeping can disrupt sleep quality and increase the risk of fatigue.
 Haskell, E., Palka, J., Walker, J., Berger, R., & Heller, H. (1981). The effects of high and low ambient temperatures on human sleep stages/Effets de températures ambiantes élevées basses sur les stades de sommeil chez l’homme. Electroencephalography and Clinical Neurophysiology, 51(5), 494-501.