Damp sheets point to moisture. Warm sheets point to heat. Both look like a hot-sleeper problem, but they need opposite solutions.
A duvet that cools through airflow will not help if the issue is sweat sitting on your skin. A duvet that absorbs moisture will trap too much heat if the room is already warm and you are not producing moisture overnight. The fill has to match the cause.
Wool absorbs up to thirty percent of its own weight in moisture and still feels dry to the touch. The crimped fiber structure pulls sweat away as vapor and releases it gradually. That keeps the microclimate around your body dry even when you are producing moisture overnight. A crossover study of 36 adults sleeping in a warm room set to 30 degrees Celsius found older participants fell asleep in 12.4 minutes on wool versus 26.7 minutes on cotton. That is a 14-minute gap, repeated every warm night.
Cotton takes the opposite route. The weave stays open and heat flows through it constantly. There is no moisture absorption happening inside the fiber. Cotton cools by letting air move, so it works when the room is warm and you need steady ventilation, not when your body is generating sweat that has nowhere to go.
Three checks to run. If sheets or pajamas are damp more than twice a week, that points to wool. If the room feels too warm before you climb in, that points to cotton. If you are in perimenopause, menopause, or on a medication linked to night sweats, that points to wool again.
Wool also creates a dry, low-humidity microclimate and carries natural lanolin, so dust mites struggle to settle in. Cotton is plant-based, so it is the pick if you want a vegan duvet.
Care differs. Wool is dry clean or spot clean. Cotton is spot clean and air in the sun. No machine washing for either.
Track two or three nights. Note whether you woke up warm or woke up damp. That picks the fill for you.
Originally published on [Circadian](https://circadianrest.com/blogs/pillow-talk/wool-vs-cotton-duvet-hot-sleepers).
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