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Which duvet is the warmest?

1 Jan, 2024
Marco Achtereekte

Which warmth class of comforters is the warmest?

Which duvet is the warmest? The answer to this question is seemingly very simple. After all, comforters from heat class 1 are seemingly always the warmest. However, before you get busy with this information. Please read on because there is more than just heat.

Thus, ambient temperature, the insulation of your bedroom, the properties of a quilt and your personal preferences also play a very powerful role. Dive into the wonderful world of duvet offerings and the theoretical explanation of how heat classes are created?

The technical explanation of heat classes

The classification below divides insulation capacity into 4 heat classes. One looks for the thermal insulation of a surface unit. This is called thermal resistance in technical jargon. In England, the so-called Tog was developed for this purpose; in the US, this isolation is expressed in Clo. For your information, 1 clo = 1.55 Tog. Specifically, down also looks at fill power.

Heat ClassAmbient temperature outsideSeasons
Heat Class 1Average 4°C or lowerVery cold winters (11 – 13.5 Tog)
Heat Class 2Average 8°CCool winters and autumn nights (8 – 11 Tog)
Heat Class 3Average 12°CMild winters and spring and autumn nights (6 – 8 Tog)
Heat Class 4Average 16°C or higherWarm summer nights (2.5 – 4 Tog)

What is a Tog?

Tog is a unit of thermal resistance used to measure the insulating properties of comforters for classification purposes. A higher Tog number represents better insulation and more heat. Tog values usually range from 1 (very light) to 15 (very hot). Nice and easy right when you can just measure thermal resistance? Yes indeed! However, it doesn’t quite complete the story because you are not measuring with this whether a quilt is insulating. Especially for down duvets, for example, this insulation value, fill power or CUIN value is very valuable.

The Tog value is very well known in Great Britain and the British Isles and is actually hardly used in the Low Countries and by extension Western Europe. A lot of producers create their own interpretation. This makes it less easy for you, as an interested consumer, to compare properly. So often a warm quilt is conveniently called a 4-season model. These quilts can be used together or as individual quilts thanks to attached “cutters” or buttons. A warmer part for the in-between seasons and a lighter part for summer, together they then form the very warm winter comforter.

What is fill power?

Fill power is a scientific yardstick to measure the quality of down. The higher the fill power, called the CUIN value, the better the quality of a duvet. Simply put: at the same fill weight, down with a high CUIN value retains more heat. More air is retained and that insulates better. You also see more volume and often that down is much fluffier. The quilt is noticeably lighter with the same thermal performance. In this example, the best quilt is the one with the highest heat-insulating property at the lowest weight.

Again, we make a small observation here, because this value is also approached theoretically. In ideal conditions, without humidity, the test is performed several times and the average is calculated. However, the humidity of your bedroom is ideally 50% on average. The moisture will cause the thermal insulation to be lower in real conditions.

What is the impact of filling on the warmth experience of a duvet?

As you can read, it seems easy to determine thermal resistance and filling power and the stocking is finished. However, we also immediately gave our comments on the results. And then there are big differences between, for example, comforters made of natural hair (wool, etc.), down and feathers, silk, bamboo, Lyocell and synthetic fibers. Because all these materials also have other properties.

This leads them to react differently with perspiration or with excess heat. In other words, what are its moisture-regulating, ventilating and heat-regulating properties? And are they hygienic to sleep under, in other words are they washable or at least cleanable? And what about allergies? Are they hypoallergenic by nature or do you really need to wash at high temperatures?

Being cold under quilt

The influence of bedroom temperature on your choice of quilt?

The ideal bedroom temperature is about 18°C. That ideal temperature applies to every season. So that means also during the colder fall and spring nights and especially during a cold winter. A lot of people choose to leave the windows open all year round in the bedroom. With respect to humidity and heat, it could be better.

During cold days, ventilate your bedroom vigorously and long enough in the morning. Then close your windows and open your bedroom door. This way you don’t let heat go to waste, and a bedroom usually warms up to about 18°C. Just before you go to sleep, put the windows back ajar or open them. You crawl into a comfortable bed and your bed textiles are also well dried during the day.

Sleeping with a window open?

If you sleep with a window open, then you know you can safely use an extra warm comforter. Do you get cold easily? Then down comforters or class 1 wool or synthetic winter comforters are a good choice. If you are always too hot consider heat regulating quilts such as camel hair, (Texeler) sheep’s wool or mixed natural hair quilts.

If you want to be able to work with 1 duvet in all seasons, there is only 1 choice: a 4-season version. The two duvets knot together to form one thick duvet. If you take off the lightest one, it is perfect for hot summer nights. The one that remains is rather medium warm and fine to keep you warm during spring and fall.

Which comforter is warmest: Conclusion

A heat class 1 is clearly the warmest variant. But look a little further than just the heat classes. Keep in mind the bedroom temperature. It is greatly determined by the insulation of your home, sleeping with windows open or closed, and whether you lightly heat the bedroom during the winter.

Also consider the specific properties of the fillings used for quilts. Down is generally highly insulating and thus warmer, while natural hair such as wool comforters are highly moisture regulating and can often regulate heat better.