Wind Speed vs. Wind Pressure Explained

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Many don’t understand how wind works & state that a product is rated to a specific wind speed.  This is false advertising & not true.

 

There’s no such thing as “Rated to XXX MPH wind”

This is frequently seen in marketing materials which is a false & misleading statement
that comes with many unwritten disclaimers.  

 

The Why

The formula that converts wind velocity to wind pressure has many variables. Each variable affects the resulting pressure for a given wind velocity.  A 100mph wind velocity for example can produce pressures as low as in the mid-teens (psf) to upwards of 50psf, even 60psf, and more*.  These variables include such features as building height, location of the area on the building, the terrain around the building, whether the building is on or near a hill, slope of the roof, size of the area in consideration, and more.

There are even two types of wind speeds and pressures that complicate things further, Allowable stress design and Load Factored Design (click here to learn more) as well as different wind codes that govern (Some use ASCE 7-05, most use ASCE 7-10, and there’s now ASCE 7-16 with yet different conversion factors for some building surfaces for the same wind velocity).  Engineers deal with a common denominator when designing structures (wind pressure) which sets a uniform standard anywhere (yes even on the moon) for a force that a product can resist.

How We can help

1) Engineering Express provides certified wind charts for permit for windows, doors, and garage doors.  Click Here to browse our plan store

2) Engineering Express also provides a free online tool to convert wind velocity to wind pressure.  Click Here to access it

 

* ASCE 7-16 Exposure D, 300 ft MRH, Zones 5 and 3 respectively, 10sqft tributary area, enclosed structure, flat terrain, Kd=0.85,  Forces upwards of 70psf + possible for hilly terrain, partially enclosed, Kd=1.0, at sea level.

Last Update: July 7, 2021  

March 8, 2018  Engineering  
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