I am not claiming to be a expert or anything like that but, I work for a window company that actually use hurricane windows and when we send out the windows to get our certification a hurricane has a push and pull effect. With the giant outdoor fan it is just trying to blow the house over. Our units need to withstand a push/pull effect for a period of time and this test didn't actually simulate a actual hurricane.
I think the Mythbusters didn't grasp the concept of this myth. This myth refers to the pressure differential caused by the sudden drop in barometric pressure outside, and the higher pressure inside, causing the house to destabilize. Huffing and puffing to blow the house down is another myth.
That might be true, but it just seemed like they were trying to blow the house apart aside from what really happens with the changes in pressure. That's where the real test to open and closed windows is going to make the difference. I really hope that re-look at this myth and try it again with pressure changes. I actually got to see hurricane windows being tested and it really something seeing them get hit with 3 2X4's before being completely broken.
I'd also like to see them try and just break one window under the pressure circumstances you guys are talking about. Living in Florida all my life, they always said thats how you lose your roof, if one window breaks the pressure pulls it off.
My only problem with the hurricane test is the 'scale' model. To me it doesn't matter if they are trying to truely replicate a hurricane or just blow the house over, there is one main problem: The scale house is not to scale. True scale models need to be made with scale materials and scale fasteners as well. For example, nail or screw 2 5' 2x4's together with 2 inch nails or screws then test the durability or force it takes to rip it apart, now take 2 1' 2x4's with the same fasteners and test it again, it will take a lot more force to destroy or rip apart the smaller scaled design. I usually hate to be picky but for true scale testing to try to destroy something, all items should be as close to scale as possible.
The scale model of the house is stronger than it should be. On the show it was supposed to be half scale. That means the 2x4 wall studs should be split in half long ways so that they are half the thickness and width to be accurate. Or use 1x2's instead of 2x4's. As well as the plywood walls would have to be half as thick.IMAGINE THIS: you have two pieces of ree-bar commonly used to reinforce concrete. One a foot long and one 6 inches long. Your not going to be able to bend the 6" piece as easily as the foot long one unless you decrease the thickness of the bar by half. So the house was not properly half scale.
Even the thickness of the glass needs to be half as thick cause a 1/4 " thick piece of glass thats 6"x6" is gonna be stronger than one that is the same thickness but 12"x12"
I guess the one thing I would really like to see would be more testing on the window part of the myth. The only window part they were testing was if the house will blow over with the windows open or closed. Lets see what it takes to blow up a window in a hurricane. Lets see different methods to hurricane proof a house. Use the obvious like the hurricane windows then 1/2 inch plywood, 3/4 inch plywood, particle board, fencing nailed over the window, etc, etc. What your trying to prevent is something breaking the window to create the pressure difference. Lets find cheap and re-useable solutions for people in hurricane area's.
In the early 60's and 70's in Florida, when a hurricane was approaching, we were advised to open only ONE window just a crack on the opposite of the winds. As the hurricane traveled past your position, and wind came from the other direction, you closed that window and opened one on the opposite side of the house. The open window was not in the direct path of the oncoming wind.
Originally posted by Venster: I think the Mythbusters didn't grasp the concept of this myth. This myth refers to the pressure differential caused by the sudden drop in barometric pressure outside, and the higher pressure inside, causing the house to destabilize. Huffing and puffing to blow the house down is another myth.
Exactly...as someone who grew up on the Gulf Coast and who has gone through SEVERAL hurricanes, I've learned all sorts of storm survival techniques from the scientific evidence provided by the federal govt. and other sources. The thing about opening windows was totally not represented properly here. The deal about the windows is to do with the sudden and dramatic change in pressure because a Hurricane has extremely low barometric pressure. Also, opening all windows would OBVIOUSLY be a really stupid thing to do. They only simulated wind and rain but NOT the huge change in pressure. Everyone down here knows to board up your windows but they also know to crack a few of them open slightly to ensure that the pressure change doesn't cause the windows to shatter. Ask anyone who lived through Camille, which had the lowest ever recorded barometric pressure of any hurricane, and they will tell you about the dangers of keeping all windows completely closed. I'm a huge fan of Mythbusters, but this episode actually ticked me off.
This message has been edited. Last edited by: mod_ivy,
Originally posted by Roughneck979: The scale model of the house is stronger than it should be. On the show it was supposed to be half scale. That means the 2x4 wall studs should be split in half long ways so that they are half the thickness and width to be accurate. Or use 1x2's instead of 2x4's. As well as the plywood walls would have to be half as thick.IMAGINE THIS: you have two pieces of ree-bar commonly used to reinforce concrete. One a foot long and one 6 inches long. Your not going to be able to bend the 6" piece as easily as the foot long one unless you decrease the thickness of the bar by half. So the house was not properly half scale.
But the winds weren't scaled down. Your argument only makes sense if the winds were scaled down.
Absolutely, you need to scale down the structure but you can't just reduce the member sizes in half, you would have to analize the section properties of your studs such as the section modulus so you can size them so they have a true 50% max load resistance of a 2x4. Diflection of the structural members should also be looked at.
I agree with the statement that the scale house being too strongly built.The most destructive part of a hurricane is not the wind but the water. Coming from the North,I have heard this myth being more for tornados than for hurricanes.
This seems pedantic. They scaled the house down in order to fit into the field of action Florida's hurricane machine. Within that field of action, the machine produced winds typical of a category 2 hurricane. That is to say, it was a smaller hurricane, not a half power hurricane. If you resized all the materials, you'd weaken the structure in comparison to the wind forces, only succeed in making a doll house.
The pressure drop thing is truly a myth. The pressure does not drop that fast in a hurricane for the differential to ever be enough to be significant. Even in a tornado, which has much quicker pressure drops, the chance of it being the determining factor in structure damage is pretty much non-existent.
As mentioned elsewhere ... they only tested this with a one room house (and I don't know too many houses that are one room houses) with windows on four sides. In a multi-room house the wind load would be much different. Not to mention things like garages, etc, which can create a very nice "wind catcher" that can cause blowout damage to the structure. Also, if the foundation is weak, the structure can slide very easily especially with these "wind catchers".
Originally posted by wx3i: The pressure drop thing is truly a myth. The pressure does not drop that fast in a hurricane for the differential to ever be enough to be significant.... As mentioned elsewhere ... they only tested this with a one room house ... Not to mention things like garages, etc, which can create a very nice "wind catcher" ..." .
All good points, I would expect the eves of a roof that hang over the edge of the outside walls would make a very good wind catcher to lift the roof right off. Also, you probably don't need much of a pressure differential to destabilize a house under these conditions. Wood structures are flimsy enough already.
Remember this "myth" started back in the early days of the 20's and 30's when construction techniques were different than today.
I know online I saw a house make it through a hurricane, it was called a monolithic dome. Correct me if I am wrong but any kind of new construction in hurricane zones actually have to be built stronger to help with making sure the roofs won't fly off etc, etc.
Originally posted by Venster: I think the Mythbusters didn't grasp the concept of this myth. This myth refers to the pressure differential caused by the sudden drop in barometric pressure outside, and the higher pressure inside, causing the house to destabilize. Huffing and puffing to blow the house down is another myth.
Exactly...as someone who grew up on the Gulf Coast and who has gone through SEVERAL hurricanes, I've learned all sorts of storm survival techniques from the scientific evidence provided by the federal govt. and other sources. The thing about opening windows was totally not represented properly here. The deal about the windows is to do with the sudden and dramatic change in pressure because a Hurricane has extremely low barometric pressure. Also, opening all windows would OBVIOUSLY be a really stupid thing to do. They only simulated wind and rain but NOT the huge change in pressure. Everyone down here knows to board up your windows but they also know to crack a few of them open slightly to ensure that the pressure change doesn't cause the windows to shatter. Ask anyone who lived through Camille, which had the lowest ever recorded barometric pressure of any hurricane, and they will tell you about the dangers of keeping all windows completely closed. I'm a huge fan of Mythbusters, but this episode actually ticked me off.
Are you serious? What government group did you get your information from? The Lets Make Stuff Up group??? NOAA says it best. NO HOUSE IS AIRTIGHT TO START WITH ergo its a stillborn myth. It doesn't matter if the windows are closed. http://www.aoml.noaa.gov/hrd/tcfaq/C6.html
