Watch the video on Impact-Resistant Windows.
Coastal homeowners from Maine to Texas can probably guess what Ivan, Frances, Charley, Jeanne, Isabel, Bonnie, Fran and Andrew have in common. They were hurricanes that resulted in over a billion dollars worth of damage in the past two decades.
Tropical storms officially become hurricanes once they grow to having sustained winds in excess of 74 miles per hour, but gusts as low as 50 miles per hour are strong enough to cause major damage.
During high winds, debris can act with enough force to break windows and let water into the home. Winds can create lift the roof, push the walls outward, and collapse the structure.
Fortunately, now there's a product on the market that can provide better protection for the home and peace of mind for the homeowner. Impact resistant windows are becoming more and more common in coastal communities. Besides protecting the interior of the home from water and wind damage, they also increase the stability of the building envelope, reducing the risk of catastrophic structural failure from hurricane winds.
The process of creating impact resistant windows starts at a factory that makes a sandwich of multiple laminates, usually polyvinyl butyral (PVB), between two sheets of glass. This sandwich is then heated to melt the laminates together and release any air trapped between the layers.
Next, the glass is placed in a high-temperature, high-pressure autoclave that tempers the glass to its final impact resistant strength. The sheets are then cut to size and framed.
To be certified as impact resistant, the windows must pass a battery of tests. While the glass is expected to break during these tests, it shouldn't shatter or be pushed out of the frame. Often state and local building codes determine the specific thresholds, but generally all windows must pass the following tests:
- The first test is called a launch missile impact test. A 9-pound 2x4 wood stud is launched at 50 feet per second (fps), or almost 35 miles per hour, at the center of the window. If the window doesn't shatter, another board is then shot at one of the corners of the window. Both the center and the corner of the window must be able to hold together to pass this test. Hurricane-prone Florida has slightly tougher testing standards, requiring windows to withstand boards launched at 80 fps.
- After the launch missile impact test, the window is then subjected to pressures that simulate winds of up to 200 miles per hour. If the window remains intact within the frame, it can be certified as an impact resistant window.
For homeowners who don't have impact resistant windows, the most common method for protecting windows is to board them up or cover them with protective plywood sheets. While this method is better than not doing anything, it relies on conditions that aren't always practical for the homeowner.
First, there must be ample warning that a hurricane is coming to allow the homeowner enough time to collect and install the materials. Also, the supply of materials can quickly be exhausted in coastal areas as a storm approaches. And this method requires the homeowner to be at home and physically able to install the protective sheets. This task can be impossible for older homeowners, and it can be impossible for everyone if there's an order to evacuate the area.
Because hurricane-prone coastal areas remain one of the highest growth areas for new construction in the United States, builders will be asked to help homeowners find ways to protect their investments. Impact resistant windows are a great way for the builder to offer the homeowner a first line of defense against wind.
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