A long standing tornado myth states that if you open windows in a tornado, it will prevent the roof from being blown off. There’s another myth that says you should only open north facing windows. I’m not sure where these myths originated, but they are both pretty silly and could be potentially fatal in that they mislead the homeowner into a false sense of security. It’s really a matter of simple physics. Watch the small video to the left. Open Windows would not have made difference and the outcome would have been exactly the same; the house would still have been destroyed.
The roofs on most well constructed houses are held together by steel “L” brackets, a lot of nails, and 2×4 wood beams (or trusses). A window is nothing more than about a 1/4 inch pane of glass. If this myth were true, in that a closed window could be responsible for causing the roof to blow off, that is saying the glass is stronger than the construction of the roof, and that by opening the windows, the air will have an escape instead of launching the roof off the top of your house. This simply isn’t true.
If the winds that make a tornado are strong enough to hurl a car or a train car hundreds of feet through the air, and even scour asphalt off the road, then your windows being open or closed won’t make the slightest bit of difference when the tornado hits. The other argument that opening the windows on one side of the house and not the other might cause more internal air pressure because the air won’t have an escape out the other side is also false. The same principal applies. The glass window will give out and break far before the roof or walls do. Despite what some think, the air pressure differential or “sucking” of the tornado doesn’t cause a house to explode. It’s the brute force strength of the wind, which can reach speeds in excess of 200 mph.
The air pressure differential between the inside of your home and inside of a tornado is not that great. The Texas Tech’s Institute for Disaster Research conducted several experiments and concluded that the pressure drop found inside a tornado with a wind speed of 260 mph (just shy of an F5 tornado) was only about 10%. That’s about 1.4 pounds per square inch which really isn’t that much. Most well built houses and buildings can vent this great a pressure change with no ill affects on the dwelling, even if all the windows and doors are closed. There are attic openings, chimneys, furnace vents, and other small openings underneath doors and closed windows for which the air can escape. It’s not the pressure differential that destroys a house when a tornado hits, even though it may look like the house is exploding.
There are two things associated with tornadoes that can destroy a house. First and foremost, the wind. A wind clocked at 260 mph is going to flatten just about everything in its path regardless of the windows being open or closed. The broadside of a house is going to act like a sail and whether you have a 4’x4′ window sized hole isn’t going to make a bit of difference. Second of all, wood beams, trees, large debris, and a million bricks from your neighbors house will become airborne missiles. So again, opening the windows during a tornado isn’t going to minimize the damage to your house one single bit.
The best thing you can do is save the time you would wasted opening the windows by seeking shelter sooner. Watch the news if there is the threat of severe weather. If a tornado is heading your direction and you cannot escape, the safest place to be is below ground in a storm shelter or basement. If that isn’t possible, then the next best places are either in an interior closet on the first story or a bathtub. If you see the tornado, do not try to outrun it in your car.