Sleeping with the window open in winter: Which bedding keeps you warm?
Many people sleep with a window tilted open or wide open all year round – and in November they suddenly find that their bed can no longer keep up. Those who want to sleep with an open window often have a bedroom temperature of 12 to 14 degrees at night instead of the usual 17 to 18 degrees. There is no simple answer as to which bedding will retain the heat: it depends on how cold the room really gets, how quickly you feel the cold – and what lies beneath the duvet.
What really matters when a window is open in winter
1. How cold it actually gets. There can easily be a difference of four to five degrees between a window tilted open in a well-insulated apartment and a window wide open in an old building. It is also crucial whether cold air blows directly over the head of the bed. Where a draft hits the shoulders and neck, a thicker cover won't help, but rather a different bed position – or a fabric that retains the heat directly against the skin.
2. Fiber and surface weight. Heat is not created in the fabric itself, but in the air that it traps. Brushed cotton such as flannel creates a fine nap: flannel weighs around 160 g/m² and stores a layer of air in these raised fibers that feels warm immediately upon getting into bed. Fine flannel is lighter and more finely brushed, while Nicki uses a velvety nap that warms up particularly quickly but absorbs very little moisture.
3. The whole bed, not just the cover. The most common source of error: a warm duvet cover on top, a thin jersey sheet underneath. The mattress then becomes a cold bridge – the back and feet remain cold, even though the duvet is right. Those who sleep with an open window should consider the sheets and pillowcases just as carefully as the duvet cover.
Comparison of warm qualities
| Quality | Property | Ideal for | Price range (135x200 + 80x80) |
|---|---|---|---|
| Melange flannel | 100% cotton, woven from differently colored yarns instead of printed; just as warm as flannel, but with a finer, softer feel | Very cold rooms, sensitive skin, long-term use | approx. €49.95 – €64.95 |
| Flannel / Fine flannel | Brushed cotton with a strong nap; flannel around 160 g/m², fine flannel lighter and finer | Classic winter warmth with a design, rooms around 15 – 16 degrees | approx. €49.95 – €59.95 |
| Nicki | Velvety nap, warms up very quickly, but absorbs little moisture | Guest rooms, youth rooms, small budget | approx. €27.95 – €32.95 |
| Renforcé / Jersey | Smooth or elastic, no nap – feels cool when getting into bed | Heated rooms, not for open windows in winter | available year-round |
Which bedding is right for you?
You sleep with a window wide open and get cold quickly. Then Melange flannel is the safest choice. The quality was developed in 2012 at biberna as "Flannel 2.0" and is still woven in the company's own weaving mill in Hamminkeln to this day – from differently colored yarns instead of being printed, making it mottled and particularly soft. Specifically: the biberna Melange flannel bedding, item number 0840500, from €49.95 in 135x200 cm.
Your window is only tilted open, and the room remains at 15 to 16 degrees. Here classic fine flannel is sufficient, and you have a larger selection of designs. One example from the winter bedding: the biberna Fine flannel bedding Stripes, item number 0007253, from €49.95. Fine flannel sets are made according to biberna specifications, tested and shipped in Hamminkeln.
It should above all be warm immediately and cost little. For guest rooms or a cool youth room, Nicki is the practical solution: The velvety nap warms up faster than cotton. The Castell Nicki bedding, item number 0380746, is €27.95 for 135x200 cm. However, those who sweat heavily at night are better off with cotton.
The duvet is right, but the bed still feels cold. Then it is the sheet's fault. A brushed fitted sheet changes the feeling of getting into bed more than any change of cover: the biberna Melange flannel fitted sheet, item number 0841380, from €23.95, or the biberna Fine flannel fitted sheet, item number 0002744, also from €23.95. Both come from the company's own weaving mill in Hamminkeln and can be found in the Flannel fitted sheets collection.
What is often overlooked
Moisture. Cold outside air absorbs little moisture. The fabric must therefore buffer what the body releases at night. Cotton can do this, pure synthetic fiber hardly at all – that is exactly why Nicki or fleece bedding sometimes feels clammy in the morning with an open window, while flannel and Melange flannel remain dry.
Care. The nap is what you are paying for – and it suffers above all from fabric softener, which settles on the raised fibers and flattens them. Otherwise, follow the care label of the respective set; brushed cotton generally tolerates much more than velvety synthetic fiber.
Durability. A densely woven winter quality lasts many seasons, but loses a little nap with every wash. Thin cheap goods lose it in a single winter. Therefore, do not calculate the price per set, but per season.
And shipping. At biberna, we deliver all products within Germany free of charge, with no minimum order value – even a single fitted sheet.
Frequently Asked Questions
Is sleeping with an open window in winter sensible?
Fresh air lowers the humidity in the bedroom, and many people sleep more deeply in cooler air. The crucial thing is that the body still stays warm – that is exactly what bedding does. Those who are constantly cold wake up more often; then it is not the window that is the problem, but the cover that is too thin.
Does Melange flannel warm more than flannel?
No. Both qualities warm equally well. The difference lies in the feel: Melange flannel is finer and softer because it is woven from differently colored yarns instead of being printed. Those who like it particularly soft on the skin should choose Melange flannel; those looking for the strong, classic nap should choose flannel.
Is Renforcé enough if I have a thick duvet?
The duvet determines how much heat is stored – the cover determines how the bed feels in the first few minutes. Smooth qualities without a nap feel cool when getting into bed, even over a warm duvet. With an open window, that is exactly the moment when most people start to feel cold.
Do you sweat under flannel if the room does get warm?
Flannel is pure cotton and absorbs moisture instead of retaining it against the skin. Synthetic fiber qualities are more problematic. If you fluctuate between feeling cold and sweating, Melange flannel is the more tolerable compromise.
Do I really need a warm fitted sheet too?
If the back or feet remain cold, even though the duvet is sufficient: yes. The sheet lies directly on the mattress and thus directly against you. A brushed fitted sheet made of flannel or Melange flannel is the most affordable single measure to make a cold bed warm.
And the pillowcase?
The cold draft hits the head of the bed first. A pillowcase in the same warm quality as the duvet cover makes a noticeable difference here – many sets already include it, and individual pillowcases are also available in the Pillowcases collection.