Filling the duvet regulates sweat
Who sweats a lot at night, probably has the wrong filling in his blanket. In down you sweat a lot, because it comes to a high heat development. Down comforters are therefore completely unsuitable for people who sweat easily.
Unlike feather beds. The heat development is low here. Who transpires, should pay attention to the highest possible proportion of feathers in his blanket. So the mix does it. In addition, of course, as a factor, the fresh air supply in the bedroom and the temperature control (heating).