Aafke Van der Ende, sleep expert: “A room that is too humid is ideal for mites to appear”

Sleeping with the window open is second nature for some people and completely unthinkable for others. While some swear they need fresh air to fall asleep, others say they can’t rest at all under those conditions. According to sleep expert Aafke Van der Ende, speaking to RTL, there’s no one‑size‑fits‑all rule.

Why bedroom temperature matters

The temperature of your bedroom has a direct impact on sleep quality. Van der Ende says the ideal range is about 60–65°F, since the body naturally cools down at night. If the room is too warm, your body struggles to release heat, and your sleep suffers.

Opening a window can help reach that cooler temperature—especially in the summer, when nighttime air tends to be fresher. In winter, though, leaving the window open can make the room too cold. In those cases, she recommends airing out the room at other times of day instead.

Ventilation and air quality

Throughout the night, we exhale carbon dioxide and release moisture through breathing and sweating. Without enough ventilation, the air can become overly humid. Van der Ende warns that a damp bedroom creates the perfect environment for dust mites and mold.

The downsides of sleeping with the window open

There are drawbacks, too. Outdoor noise—traffic, late‑night conversations, sirens—or simply feeling unsafe with an open window can make it harder to fall asleep. The expert also notes that stressing too much about doing everything “perfectly” can backfire and make sleep even more difficult.

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