Opening windows does not balance pressure, but invites wind into the house. The internal wind pressure pushes up against the roof and out through the walls, increasing the risk of structural collapse and roof damage.
When natural disasters like storms and floods strike, we often feel fear and try to protect our possessions. One common misconception is that opening windows during a storm can prevent a house from “exploding” due to pressure differentials.
In preparation for Typhoon No. 3, many people stayed home and reinforced their houses. (Photo: Xinhua).
As Typhoon Yagi approached Vietnam on the afternoon of September 7, a post on Threads circulated this information, advising those in the storm’s path to open their windows to “balance the pressure” inside the house and minimize damage. The post attracted numerous comments and shares.
Immediately, many users requested the account owner to delete the post to avoid spreading misleading, unscientific information during this critical time. The post has since been removed.
In reality, the belief that opening windows during a storm can “balance pressure” originated from significant damages caused by storms in the early 20th century. At that time, many people observed that roofs were often blown off during tornadoes, leading them to believe that internal pressure was the culprit.
They thought that opening windows would relieve pressure inside the house, preventing the roof from being lifted and thus avoiding catastrophic damage. Consequently, this became a widely accepted piece of advice during tornadoes and storms.
However, many subsequent studies have completely debunked the idea that opening windows during severe storms can help balance pressure.
Opening windows invites wind into the house, potentially lifting the roof
To understand why opening windows is ineffective and can be dangerous, we need to examine how wind affects buildings during severe storms like Yagi. When storm winds or tornadoes strike a building, they do not create uniform pressure around the house. Instead, they create areas of positive pressure on the windward side (the side facing the wind) and negative pressure on the leeward side and the roof.
A small house in Cam Pha city, Quang Ninh province suffered roof damage, losing many belongings. (Photo: Viet Linh).
As wind blows over the roof, it generates lift similar to how airplane wings create lift. This effect, combined with wind entering through gaps in the building, can cause the roof to be lifted off.
However, when wind enters a building through an opening (such as an open or broken window), it increases the internal pressure. This pressure pushes up against the roof and out through the walls, combined with external forces, which can lead to complete structural failure.
Leaving windows open will not balance pressure as many believe. Instead, wind will enter the house and become trapped inside, exerting pressure on the roof and walls from within.
One of the greatest dangers during storms and tornadoes is debris from objects that can injure people and animals. Anything from branches to roof tiles can become hazardous in strong winds.
If you leave windows open, you are not only “inviting” wind into the house but also allowing dangerous debris to enter. A stone, a tile, or a piece of wood propelled by the storm winds could shatter windows, destroy belongings, or even injure or kill those inside.
What to do when a storm approaches?
The Office of Science and Society at McGill University explains that if houses were designed like empty boxes, wind could pass through, reducing overall pressure on the structure. However, homes in Vietnam are not simply empty boxes; they are often narrow, adjoining houses or apartments.
Hallways, walls, and doors create internal barriers that prevent wind from circulating within the house. When wind enters through open windows, it gets trapped at these barriers, causing pressure to be unevenly distributed throughout the house, which can weaken the structure and make it more susceptible to collapse.
One of the most significant findings that debunked the myth about opening windows came from studies on tornado damage, particularly after the Wichita Falls tornado in 1979 in Texas.
Researchers found that when windows were left open or broken by debris, wind entering the house increased internal pressure on the roof. At the same time, winds blowing over the roof created lift like airplane wings. These forces combined increased the risk of roof damage.
Glass windows at a showroom in Hanoi are reinforced. (Photo: The Bang).
If the roof is lifted during a storm, the walls of the house become much more prone to collapse. The roof helps keep the walls connected. When it is lost, the walls risk tipping over, making it seem as if the house “exploded.”
Therefore, the most important thing you can do to protect your home during a storm is to keep all windows and doors tightly closed.
You should also close all interior doors. According to the Insurance Institute for Business and Home Safety (IBHS), closing interior doors can reduce pressure on the roof by 30% during a storm. By breaking up the pressure into smaller areas, the likelihood of the roof being lifted decreases.
The Federal Emergency Management Agency (FEMA) recommends sealing garage doors and, if possible, reinforcing them. Garage doors are often the largest openings in a house. If wind gets through this door, it can cause significant damage to the entire structure.
