How to Keep Your Room Cool

If your room does not feel cool even when the air conditioner is running, or if heat seems to linger into the evening, the issue may not be how you are using the unit but the environment itself. By paying attention to a few key factors—such as blocking heat, ventilation, and temperature management—you can stay comfortable while reducing energy use.

Ventilate Before Turning On the Air Conditioner

When you return home, the air inside may feel hotter than the air outdoors. This happens because heat accumulates inside a closed room. Turning on the air conditioner in this state forces the unit to work harder to remove the accumulated heat, increasing energy consumption. Instead, start by opening the windows to create airflow and let the hot air escape. Ventilating the room before switching on the air conditioner can improve cooling efficiency and help avoid unnecessary energy use.

Be Mindful of Doors and Windows

When the air conditioner is running, leaving doors or windows open allows cooled air to escape. This reduces cooling efficiency and forces the unit to use more energy to maintain the desired temperature. To prevent this, keep windows properly closed and avoid drafts from outside. When entering or leaving a room, open and close doors quickly and make sure they are fully shut. Small habits like these can make a noticeable difference.

Use Natural Cooling Methods

Water absorbs heat as it evaporates—a process known as evaporative cooling. By using this natural effect, you can create a cooler environment without relying only on the air conditioner. For example, sprinkling water on the ground lowers the surface temperature, and doing so in the evening helps the effect last longer. Hanging a wet bedsheet outside an open window can also help cool the air before it enters the room.
These methods tend to be most effective in dry conditions. In addition, opening two or more windows to let air flow through the room helps prevent stagnant air and can make the space feel cooler regardless of humidity.

Make Better Use of Curtains and Blinds

Making good use of curtains and blinds can be an effective way to keep the sun’s heat from entering the room. Light-colored fabrics, such as white, are recommended because they reflect sunlight and infrared radiation, helping limit heat build-up. Darker colors, on the other hand, tend to absorb heat and may contribute to higher indoor temperatures. Applying heat-blocking film to window glass can further reduce the amount of heat entering the room.

Understanding the Risk of Indoor Heatstroke

Heat absorbed by ceilings, walls, and floors during the day can remain indoors at night, causing the room to stay warm. In conditions like these, the risk of heatstroke can increase—even indoors. If you notice symptoms such as fatigue or thirst, be sure to stay hydrated, wipe away sweat, and cool your body as needed. If you continue to feel unwell, avoid pushing yourself and seek help when necessary.

Creating a Comfortable Sleep Environment

A comfortable night’s sleep depends on maintaining an appropriate balance between temperature and humidity. On hot and humid nights, using the air conditioner’s timer function can help prevent overcooling by turning the unit off automatically after you fall asleep. If you prefer to keep it running through the night, a setting of around 26℃ can help maintain comfort without excessive cooling.