Wind Storm Tests
Wind storm Codes & Standards in the U.S.
ASTM E1886-97: TEST METHOD FOR PERFORMANCE OF EXTERIOR WINDOWS IMPACTED BY MISSILE(S) AND EXPOSED TO CYCLIC PRESSURE DIFFERENTIALS
This test method determines the performance of exterior windows (along with walls, doors, and storm shutters) when faced with missile impacts and air pressure. A missile propulsion device, an air pressure system, and a test chamber are used to model the same conditions found in a windstorm environment including wind-borne debris. This test method determines which elements of a building remains un-breached during a windstorm.
ASTM E1996-99: Covers required Test E 1886 specifications for exterior windows, glazed curtain walls, doors and storm shutters used in buildings located in geographic regions that are prone to hurricanes.
SOUTH FLORIDA BUILDING CODE – DADE COUNTY PROTOCOL
Hurricane Andrew swept through southern Florida and became one of the most destructive hurricane of all time. Afterwards, an investigation unveiled a multitude of problems with existing building construction. Weak building codes, cheap materials and poor construction compromised the structural integrity of many homes and offices. The findings centered on the separation of windows, doors and roofing materials during Andrew that turned into destructive flying objects. This debris would then shatter and break many glazing systems and doors. As a result a new South Florida building code was enacted, known widely as the Dade County Protocol, for new building construction in the region. The code's primary goal was to protect residential homes and commercial buildings from wind-borne debris.
It's important to note that many states with similar windstorm threats have adopted the Dade County Protocol building code.
Dade County Protocol Tests
The Dade County tests focus on two windstorm related areas – impact and pressure
Impact Test 1 – Large Missile
Any window, door or skylight located at ground level up to 30 feet must pass the large missile test under the Dade County code.
Two 9 lb. 2 x 4’s are launched from an air cannon at a glazing system with a speed of 34 mph. A manufacturer looking to qualify must provide 3 window samples and survive impact to the center of the glazing system as well as the corner of the window.
Impact Test 2 – Small Missile
The small missile test uses smaller projectiles (5/8” steel ball bearings) to simulate debris more likely to strike a structure above 30 feet. As with the large missile test, the supplier provides 3 samples, but this test includes 10 impacts to the center of the window, 10 along the edge, and 10 near the corner.
All 3 samples must survive the smaller missile test to pass.
Pressure Test
The glazing system then needs to pass a pressure test under the Dade County Protocol. A wind-load cyclic pressure test is conducted to simulate actual hurricane forces using 9,000 variable wind cycles.
To pass, the window must remain inside the frame and not have a crack longer than 5” or wider than 1/16”.
Security film is not an approved protection system under the Dade County Protocol. First, it does not meet the standards under the large missile test. Unfortunately, too much weight is placed on the large missile impact test because it’s a relatively unlikely event during most hurricanes. Separate studies have shown the likelihood of a large missile impact is less than 5%. Additionally, no security film has ever passed the Pressure Test. Similar to the bomb blast tests, a window is not certified under the Dade County Protocol unless that specific window/film/glass combination is tested.
Many experts believe the Dade County Protocol is overkill. Created by lobbyists of the laminated glass industry to prevent Security film application (After all, an air cannon will shoot through most walls – why is the focus only on windows?). The good news for window film is the Dade County code does not apply to existing buildings or homes - it only applies to new construction. Therefore, Security film is a cost-effective, upgrade solution to increase safety in high risk windstorm locations.
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