A bed is not one temperature. It changes through the night, as you do.
Cashmere is a fibre that works with that rhythm rather than against it. It regulates temperature, holding warmth when the room cools and letting it go when it does not, which is why a cashmere duvet settles over you rather than weighing on you.
That behaviour depends on the fibre itself. We choose Grade-A cashmere, ethically sourced, because the finer and longer the fibre, the more quietly it does this, season after season.
It is a simple idea, and an old one. A good bed is not the warmest one. It is the one that stops you noticing the temperature at all.