Why do you care if your windows are impact rated? And what does it really mean, anyway? For someone who’s new to coastal living, these may be concepts that have not been an issue in previous home ownership situations. But for anyone living in a hurricane zone, it’s important to understand how to protect your home in case of a storm.
During a hurricane, or any storm with strong winds, the greatest danger to a building comes from wind entering the structure. Windows are a vulnerable element in any building. High winds can pick up objects – broken tree limbs, outdoor furniture, signs, etc. – and hurl them about with great force. If one of these objects strikes a window and the glass is broken, this creates an opening that allows wind to enter. Although it seems implausible, wind uplift can actually tear a building apart. If a wall is punctured, the wind enters and then needs a place to escape. This creates tremendous pressure from the inside, and if it continues to build, can eventually overpower the elements that hold the home together.
Traditionally, storm protection has often taken the shape of sheets of plywood fastened over windows from the outside. While it can be quite effective, this strategy has some major drawbacks. It’s a lot of work to cover all the windows in a home, and can be difficult and dangerous. It needs to be done properly, or the sheets of plywood can be torn off and become projectiles themselves. If you’re not home when a storm approaches, or are not capable of doing this work yourself, who’s going to do it for you when your friends and neighbors are all busy protecting their own homes? Even if you manage to get the job done, you’ll need to undo it when the storm is past, and you’ll be left with nail or screw holes in your house. You may be thinking, what about shutters? Yes, shutters can also serve as storm protection, but they need to be operable and sturdy enough to serve the purpose. And in either case, you’re sitting in a dark house until the storm passes, quite probably without electricity.
Impact-rated windows are designed to prevent penetration in several ways. The glass consists of two panes of glass (generally tempered or annealed) with a sheet of high-strength membrane laminated in between. When a projectile hits it, the glass may break, but the shards will stick to the membrane and the membrane will remain intact (up to its rated impact-resistance). No flying pieces of glass to cause injury, and no hole to let wind and weather in. Also, the frames are designed so that they are strong enough to hold together in case of an impact. And the sashes (the movable parts of a window) are designed so that they stay in place and don’t become dislodged from the window frame. All of this adds up to a system that protects homes and their occupants without the need for special storm preparation and while allowing daylight into the home in the normal way.
Even though impact-rated windows are generally much more expensive (they can cost twice as much or even more) than ordinary windows, they offer huge benefits in terms of safety, security, comfort, and peace of mind.
Vernacular Green Design 