Why Closed Windows Are Not a Good Idea in Hot Weather

Why Closed Windows Are Not a Good Idea in Hot Weather

During the summer, most people close their windows to keep the hot air out. However, it could be more beneficial to keep windows open even in extreme heat.

While summer heat can be pleasant, few enjoy sweltering indoors. To combat high temperatures, people often lower blinds and draw curtains to keep their rooms cool. However, those who stay home during the day often crave fresh air, leading to evening ventilation. So, should windows be opened even in extreme heat?

So what is the issue with closed windows? Many people keep windows closed during extreme heat to keep it out, but this can be counterproductive. The best ventilation practices depend on the building structure. For instance:

  • Ground Floor and Semi-Basement Apartments: In solid buildings, the indoor climate often remains cool even on hot days. Here, it's advisable to open windows only when the indoor temperature becomes unbearable to create a draft.

  • Basements: If the outside temperature is 25 degrees Celsius or more, keep basement windows closed during the day. Otherwise, condensation can form on cold basement walls, leading to mold growth.

  • Upper Story Apartments: Due to their elevation, upper story apartments can receive more direct sunlight, making them prone to overheating. Windows should be opened at optimal times. 

Despite high temperatures, opening windows can be beneficial. Staying indoors with closed windows increases humidity, making the heat more unbearable. Although the incoming air might be warmer, the draft it creates, especially when supported by fans, has a cooling effect overall and helps keep humidity at a comfortable level.

Optimal Ventilation Strategies

A sensible approach is to open windows in the early morning or late evening when outside temperatures are lower. This allows fresh, cool air to circulate through your home without heating up the rooms during the day. Additionally you can take these measures:

  • Use Fans: Fans can enhance the cooling effect of the draft, making the indoor environment more comfortable.
  • Portable Air Conditioners: These can help maintain a comfortable indoor climate while keeping windows closed, preventing hot air from entering.