An unheated room stresses your body by constricting blood vessels, raising blood pressure, and thickening blood, increasing risks for heart attacks, strokes, and respiratory issues like asthma/COPD, while also harming mental health and sleep quality, especially for vulnerable groups like the elderly and young children, potentially leading to severe outcomes like hypothermia.
As outlined in this chapter, cold indoor temperatures have been associated with increased blood pressure, asthma symptoms and poor mental health. Cold homes contribute to excess winter mortality and morbidity.
Sitting or sleeping in a cold room is not good for you and increases the risk of heart attack, stroke, chest infections and breathing problems. “Try to keep indoor temperatures to at least 18c if you can, we have included information about help available with heating costs in the tips below.
A cooler room helps your core body temperature drop, which tells your brain it's time to rest. This natural signal can help you fall asleep more quickly and reduce restlessness at bedtime. You may stay in deep sleep longer. Overheating can disrupt your sleep cycle.
It's important to note that an indoor temperature of less than 16°C increases the risk of asthma and other respiratory conditions while going below 12°C puts the cardiovascular system under stress. A cold home can also increase your risk of depression and confusion.
Do You Get Sick from Being Cold? While it's advice you've heard for years, Fecher says it's true, but not in the sense of getting a cold virus or the flu. “You can't get sick from being cold in general, whether you're outside or inside,” Fecher says.
Sleeping too cold
“When we're cold, our body kicks into high gear to try and get us warm again,” says Dr. Drerup. Blood vessels become constricted, breathing becomes shallow and it puts extra pressure on our cardiovascular system to get our body temperatures regulated again, she adds.
The best room temperature for sleep is between 66 to 72°F. Your skin should ideally be between 88 to 95°F during sleep. The temperature under your bed covers should be around 90 to 93°F with 40% to 60% humidity.
The 3-2-1 bedtime method is a simple sleep hygiene strategy: stop eating 3 hours before bed, stop working 2 hours before bed, and stop using screens (phones, tablets, TVs) 1 hour before sleep, helping your body transition to rest by reducing stimulants and digestive load for better sleep quality. A more detailed version adds 10 hours (no caffeine) and 0 (no snoozing) for a 10-3-2-1-0 rule.
Cold sleep can activate brown fat, which may help boost metabolism and support calorie burn. A chilled bedroom supports natural hormone production, including melatonin and growth hormone, which play key roles in sleep, immune health, and overall well-being.
In Japan, it is standard practice to heat only the living room, rather than heating the entire apartment or house, as seen in Europe and America. It is not common to heat the bedroom in Japan. As a result, average bedroom temperatures are much lower in Japan.
Recognize the warning signs of hypothermia
Thicker Blood: Cold weather can cause your blood to become denser, increasing the risk of clotting. This is particularly dangerous for individuals with existing vascular conditions like deep vein thrombosis (DVT) or peripheral artery disease (PAD).
Signs and symptoms
Type C: Moderate or Temperate Climates
Often described as moderate in temperature and precipitation, type C climates are the most favorable to human habitation in that they host the largest human population densities on the planet. Type C climates are found mostly in the midlatitudes bordering the tropics.
Cold homes are also associated with negative health outcomes more widely, including heightened risk of heart attacks, impairment in children's lung and brain development and respiratory problems, which can be exacerbated by damp and mould.
The koala is famous for sleeping around 20-22 hours a day, which is about 90% of the day, due to their low-energy diet of eucalyptus leaves that requires extensive digestion. Other extremely sleepy animals include the sloth (up to 20 hours) and the brown bat (around 20 hours), with some snakes like the ball python also sleeping up to 23 hours daily.
The 80/20 Rule means that you stick to your healthy, consistent sleep schedule 80% of the time. You then can make exceptions to your schedule 20% of the time. The 80/20 Rule allows you to “live life” and enjoy those special moments with your family.
Signs of poor core sleep (deep, restorative sleep) include waking up foggy, daytime fatigue/energy crashes, poor concentration, irritability, frequent illness, memory issues, and mood swings, indicating your brain and body aren't fully repairing and consolidating memories. You might also experience increased sugar cravings, slow muscle recovery, and a weakened immune system.
Ideal room temperature for sleeping
According to The Sleep Charity, the ideal bedroom temperature for sleeping is 16–18°C. Anything over 24°C could be too hot and make you restless, while trying to sleep in a cold room with a temperature below 12°C could make it harder to nod off.
Waking up drenched in sweat, even in cooler environments and during the winter, is a sign that you sleep hot. Excessive sweating is your body's way of telling you it's having trouble regulating your temperature. Our body temperature naturally fluctuates throughout the night as we go in and out of REM sleep.
Not only can sleeping in a colder room increase brown fat and burn more calories during the 7–8 hours of shuteye, but getting a good night's sleep will also leave you feeling more alert and better able to make healthy eating choices while awake.
Sleeping in a cold room is okay as long as you're comfortable with the temperature. The crisp air alone is unlikely to make you sick if you're healthy. However, the room shoudn't be too cold. Just as rooms can't be uncomfortable when they're too warm, the same goes for overly cold rooms.
While fans cannot lower the temperature in a room, they can create a breeze that can help cool you. As the Energy Department points out, fans “cool people, not rooms” through the wind chill effect, in which wind displaces warmer air and helps evaporate sweat from the skin, making people feel cooler.
Anything below 40° – is a high trigger for hypothermia. If you asked me anything below 55° is freaking cold out, unless you are outfitted to be in the outdoors 24/7 and to sleep outside. I would go with anything below 70 or above 75.