Maybe you like to sleep out from under covers, or have the fan on while you take your naps, but there's something about a cool breeze that makes falling asleep just so much more comfortable.
But even if you like to be toasty warm under your blankets, you should really be keeping that window open at night, otherwise you may be ruining your sleep, or worse.
Researchers have found that many people who are sleeping in enclosed spaces often have trouble falling asleep, waking up, and even report having poorer overall rest.
They decided to take 17 students of relatively good health and track their sleeping habits. They put them into two different rooms, one with the windows and doors shut, and another where either one of them were left open.
With a motion sensor on one of their arms and underneath their pillow, they measured how restless they were throughout the evening, and then asked them a series of questions after they woke up.
However, the biggest discovery came when they measured the air quality over a period of five days.
The researchers found that the people who slept in the fully enclosed rooms reported much worse sleep patterns than those who were in the rooms with better ventilation.
It wasn't the temperature or the humidity levels that caused them to get less rest either.
Air quality reports found that the students with open doors and windows had average CO2 levels of 717 parts per million (ppm). Compare this to the students in the closed room where the average CO2 levels reached 1150 ppm.
While it is a relatively low increase, this was only tested over a five day period. If you normally keep the windows closed for weeks during the winter or the whole year, you can see how this would begin to suffocate your nocturnal breathing.
Symptoms of early CO2 poisoning include constant sleepiness and the inability to concentrate. If you feel you are experiencing these symptoms you should consider keeping the window open some nights.