Do Not Keep Windows Closed All Day During Heat

What to do

Ventilate for longer in the morning and evening when the outside air is cooler. During the day, keep direct sun out with blinds, curtains, shutters or awnings.

The important exception: if the air indoors becomes humid, heavy or stuffy, open windows briefly and create cross-ventilation if you can. Five minutes of real airflow is usually better than leaving one window tilted for hours.

Why it helps

The rule “keep everything closed during the day” can protect you from hot outside air, but it is too rigid on its own. People, showers, kitchen activity, laundry and damp towels can raise indoor humidity. In smaller homes, still humid air can become uncomfortable and stressful.

A short air exchange may not lower the room temperature much, but it can reduce humidity, smells and CO2. After that, close the windows again, shade the room and keep extra heat sources low.

Watch these signs

Ventilate briefly if windows fog up, the air feels heavy, you get a headache, or the room feels unpleasantly damp despite shade. A simple hygrometer helps: if humidity climbs noticeably, a short reset is better than blindly sticking to the rule.

For older, weakened or ill people, temperature is not the only issue. Stuffy humid air can add strain. Use controlled ventilation, keep water nearby and move activity to the coolest room.

Avoid this mistake

Do not leave the apartment open to midday heat. That warms up walls, floors and furniture. Think in short windows: exchange the air, close again, keep shading.