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How Do I Know if My Windows are Impact Resistant?

Posted by Jimmy Hawley on Nov 19, 2014 1:30:00 PM

If you live in an area where hurricanes are a common natural disaster, it's important that you take precautions to prepare and protect your home from damaging winds and flying debris.


Every time a hurricane is about to make landfall, you see stories on the news of homeowners nailing plywood over their windows to protect them. Although plywood is one way to protect your windows, it's not necessarily the best way.

There are other forms of hurricane protection, such as impact windows and hurricane shutters, that will do a much better job of protecting your home's openings during a hurricane.

Impact windows are becoming an increasingly popular form of hurricane protection, but it's not uncommon for people to be unsure as to whether the windows on their home are impact resistant.

What is the difference between regular windows and impact windows?

The main design characteristic of impact windows and doors is the shatter-resistant glass that's securely fastened to a heavy duty frame. Impact resistant glass consists of two layers of glass that's bonded together by a layer of polyvinyl butaryl (PVB). If the outer layer of glass breaks, the shattered pieces will adhere to the PVB film. Even after sustaining a direct hit from a large object, the glass may crack but will not expose your home to wind and water. On the other hand, standard glass windows are made out of standard float glass that will break into large, sharp shards upon impact.

Steps to identify impact windows

Here are a few tips to help you identify whether your windows are made of impact-resistant glass:
  • Look for a permanent mark in one of the corners of the glass. The mark will include the supplier's name, place of fabrication, the date it was manufactured, thickness and any certifications or safety standards that the glass meets.
  • Check the glass for a temporary label. Although most sheets of impact resistant glass will carry a mark in the corners, the glass may have been cut in a way that excludes the mark. In this case, the manufacturer may attach a removable label that states the type of glass along with the information above.
  • Examine the reflection in the glass. If you still can't find any markings or labels on the glass, hold your hand or an object up to the glass and look at the reflection. Impact resistant glass contains two sheets of glass, and you should see two different reflections.

Why should I install impact windows?

Impact windows protect your home as soon as they're installed, meaning there's no need to prepare your windows before a hurricane. Installing impact windows that meet design pressure standards from Zone 4 or Zone 5 will prevent debris from breaking your windows, meaning you'll never have to worry about debris or rain entering your home during a hurricane. Impact windows also provide protection from ultraviolet (UV) light that causes damage to your personal property such as fabrics, photographs and paint. Impact windows protect your property from the fading and discoloration that occurs due to exposure to direct sunlight.

Tip Sheet: 12 Things You Need to Know About Impact Windows

Do impact windows need to meet any building code standards?

Impact resistant windows must meet certain guidelines in order to be sold and marketed as such. The American Society for Testing and Materials (ASTM) has strict guidelines for what windows can be certified as impact resistant. Impact windows must pass the launch missile impact test, and both the center and corners of the window must hold together to pass this test. Impact windows are also subjected to pressure that simulates wind up to 200 mph.

Impact windows are very different than most windows on the market and are usually installed by a hurricane protection company. If you're unsure as to whether your windows are impact resistant, follow the tips above or contact a local hurricane protection company. They'll be able to help you in determining whether you have impact windows in your home.
Impact Window FAQs

Topics: Impact Windows