Brief Answer: The optimal sleeping temperature is 16–18 °C room temperature. At this temperature, the body can lower its core temperature, which promotes falling asleep and improves sleep quality. However, room temperature is only half the story. The crucial factor is the microclimate under your duvet — and that depends on the duvet itself. A duvet that is too warm at 18 °C will lead to sleep disturbances just as much as a duvet that is too thin at 14 °C.
You turn up the heating at night because you're cold — and then wake up sweating. Or you open the window, freeze under the duvet, and can't fall asleep. Millions of Germans are familiar with this problem. The solution rarely lies with the thermostat alone.
Sleep research shows: Room temperature sets the framework, but the duvet determines whether you sleep well. A wrongly chosen duvet sabotages even the perfect room temperature.
Last updated: April 2026
Contents
- The ideal sleeping temperature: What research says
- Why the body needs to cool down at night
- Room temperature and duvet: The interplay
- Which duvet for which room temperature?
- Optimising sleeping temperature by season
- 7 tips for the optimal sleeping temperature
- Manufacturer's tips: The right duvet for your bedroom
- Frequently asked questions
The ideal sleeping temperature: What research says
According to sleep research, the optimal bedroom temperature is 16–18 °C. This range is recommended by the German Society for Sleep Research and Sleep Medicine (DGSM) as well as international sleep studies.
Why exactly this range? The body's core temperature drops by 1–1.5 °C during sleep. This drop in temperature is not a side effect — it is an active part of the falling asleep process. If the room temperature is too high, the body cannot release enough heat.
Temperature and sleep stages
Core body temperature directly influences how deeply you sleep:
- Falling asleep phase: The body begins to release heat through the hands and feet. A cool environment supports this process.
- Deep sleep: The lowest core body temperature is reached during deep sleep. Rooms that are too warm reduce deep sleep phases.
- REM sleep: During REM sleep (dream phase), the body regulates its temperature less effectively. Extreme room temperatures particularly disturb this phase.
Why the body needs to cool down at night
Thermoregulation is a central mechanism of sleep. In the evening, the body produces the sleep hormone melatonin, which simultaneously lowers the core body temperature. This process signals to the brain: it's time to sleep.
If the environment is too warm, this mechanism does not work optimally. The body has to sweat actively to cool down — this costs energy and disturbs sleep. Studies by the National Institutes of Health (NIH) show that room temperatures above 24 °C measurably worsen sleep quality.
Too warm vs. too cold: Which is worse?
Too warm is more problematic than too cold. A bedroom that is too warm shortens deep sleep phases and increases nocturnal awakenings. A cool bedroom, on the other hand, can be compensated for with the right duvet — the body only needs to retain the heat given off under the duvet, not actively cool down.
Room temperature and duvet: The interplay
Most guides on bedroom temperature end with the recommendation "16–18 °C". This is too simplistic. Because whether you sleep well at 17 °C depends crucially on your duvet.
The microclimate under the duvet should be 28–32 °C and a humidity of 40–50 %. These values are referred to as the thermoneutral zone — the range in which the body neither needs to heat nor cool.
The duvet as a temperature regulator
A duvet has two tasks: to store warmth and to wick away moisture. Depending on the filling material and filling weight, it performs these tasks to varying degrees:
- Down duvets have the best warmth-to-weight ratio. They warm strongly with little weight and regulate moisture excellently.
- Synthetic duvets also warm, but transport moisture away more slowly. For those who sweat, moisture can accumulate.
- Natural hair duvets (camel hair, cashmere) actively regulate temperature — they warm when it's cold and cool when it's warm.
From our production: We produce down duvets in three warmth classes: summer (light), all-season (medium), and winter (warm). The difference lies in the filling weight — for the same duvet quality (90% down, Class 1), the filling quantity determines how warm the duvet keeps you. A summer duvet in 135x200 cm contains approx. 400 g, a winter duvet approx. 1,000 g of down.
Which duvet for which room temperature?
| Room temperature | Recommended duvet | Warmth rating | Filling weight (135x200) |
|---|---|---|---|
| above 22 °C | Summer duvet (light) | Warmth level 1–2 | 300–500 g |
| 18–22 °C | All-season duvet (medium) | Warmth level 3 | 500–800 g |
| 14–18 °C | Winter duvet (warm) | Warmth level 4–5 | 800–1,200 g |
| below 14 °C | Duo-winter duvet or 4-season | Warmth level 5+ | over 1,200 g |
These values apply to down duvets. Synthetic duvets require a higher filling weight for the same thermal performance, because the thermal performance per gram is lower.
Optimising sleeping temperature by season
Spring and autumn (15–20 °C)
The ideal months for good sleep. The outside temperature can be well regulated by ventilation. An all-season duvet with a medium filling weight is the best choice — it balances out temperature fluctuations between day and night.
Summer (above 22 °C)
In summer, the bedroom temperature often rises above 24 °C. Now, a light summer duvet with a low filling weight is important. Many people do without a duvet in summer — that's not a good idea. The body needs a minimum of covering to maintain a sense of security. More on this in our guide: Summer duvet: Which material cools best?
Winter (below 16 °C)
Many people leave the window ajar in winter — the bedroom temperature drops to 12–15 °C. This is perfectly fine if the winter duvet is warm enough. A down winter duvet with 900–1,200 g filling weight reliably keeps you warm at these temperatures. Also read our guide: Winter duvet: How much filling weight do you need?
7 tips for the optimal sleeping temperature
- Thermostat at 16–18 °C: Turn down the heating in the bedroom 30 minutes before going to bed. The room doesn't have to be freezing cold — just significantly cooler than the living room.
- Ventilate briefly before sleeping: Open windows wide for 5–10 minutes instead of constantly tilting them. This completely exchanges the air without cooling down the walls.
- Two duvets instead of one: If partners have different warmth needs, use two separate duvets with different warmth levels. This is more effective than a compromise.
- Socks or warm feet: Cold feet prevent falling asleep because heat dissipation through the feet is blocked. Warm socks or a short foot bath before sleeping help.
- Right mattress: Foam mattresses store more heat than spring mattresses. If you tend to sweat, this is a relevant factor.
- Bed linen made from natural fibres: Cotton and linen wick away moisture better than polyester. This enhances the cooling effect.
- Seasonal duvet change: Use a summer duvet (May–September) and a winter duvet (October–April). One duvet for all seasons is a compromise that is rarely optimal.
Manufacturer's tips: The right duvet for your bedroom
From 30 years of experience as a bedding manufacturer, we know: Most sleep problems attributed to "wrong room temperature" are related to the wrong duvet.
The most common problem: All-season duvet in winter
An all-season duvet is designed for 18–22 °C. If you sleep at 15 °C in winter, it's not enough. Instead of turning up the heating, a winter duvet with a higher filling weight is the better solution. You save heating costs and sleep better because the room temperature remains cool.
Down vs. synthetics for temperature regulation
Down has a unique property: its loft traps air, which acts as an insulating layer. At the same time, down wicks away up to 30% of its own weight in moisture without feeling wet. Synthetic fibres cannot do this to the same extent. That's why down duvets are superior in temperature regulation — especially for people who fluctuate between feeling cold and sweating at night.
From our production: We test each batch of down according to DIN EN 12934 for fill power. The higher the fill power, the more air the down traps — and the better it insulates. Our 90% down duvets achieve a fill power of at least 600 cuin. This means: maximum warmth with minimum weight. You'll notice the difference when you switch from a synthetic duvet to a down duvet — less weight, same warmth.
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Frequently Asked Questions
What temperature should the bedroom be?
The ideal bedroom temperature is 16–18 °C. This range supports the body's natural temperature drop and promotes deeper sleep. Temperatures above 24 °C demonstrably worsen sleep quality.
Is 20 degrees too warm to sleep?
20 °C is at the upper end of the recommended range. If you use a light duvet and don't tend to sweat, 20 °C can work. For most people, however, 16–18 °C is better. At 20 °C, use an all-season duvet at most, not a winter duvet.
Why do I freeze at night despite warm room temperature?
This is probably due to the duvet, not the room temperature. A duvet that is too thin or too light cannot sufficiently store body heat — even at a room temperature of 20 °C. Switch to a duvet with a higher fill weight or a higher down content.
Which duvet for 15 degrees room temperature?
At 15 °C, you need a winter duvet with at least 800–1,000 g fill weight (for 135x200 cm). A down duvet with 90% down is ideal, as it offers maximum warmth at a low weight. Synthetic duvets would have to be significantly heavier for the same thermal performance.
Should one sleep with the window open in winter?
Yes, if you have a sufficiently warm duvet. The tilted window provides fresh air and keeps the room temperature in the optimal range of 14–18 °C. Important: The duvet must be warm enough. Invest in a good winter duvet rather than heating costs.
Which duvet for people who sweat at night?
Night sweats often indicate a duvet that is too warm. Switch to a lighter duvet with less fill weight. Down duvets regulate moisture better than synthetics — they can wick away up to 30% of their own weight in moisture. Breathable cotton bedding also helps.
Is there a perfect sleeping temperature for babies?
Pediatricians recommend a room temperature of 16–18 °C for babies — just like for adults. However, babies regulate their body temperature less effectively. Use a sleeping bag instead of a duvet and regularly check the baby's temperature at the nape of the neck.
Does sleep temperature affect the immune system?
Indirectly, yes. Poor sleep due to incorrect temperature demonstrably weakens the immune system. Sleep research shows that deep sleep, in particular, is important for immune regeneration — and precisely this phase is shortened by excessively high room temperatures. The correct sleep temperature is therefore also a health issue.