Every time a hurricane is about to make landfall somewhere along the Gulf coast or Atlantic seaboard, we see stories on the news of homeowners nailing plywood over their windows to protect them. Plywood is one way to protect your windows but there are other methods and technically advanced products that homeowners in hurricane prone areas could utilize to protect the windows of their homes.
(photo credit: SanFranAnnie on flickr)
There are two main ways to protect your windows against hurricane-force winds (other than plywood):
- Install hurricane shutters – There are a few different kinds of shutters.
- Install impact-resistant glass windows throughout the home.
I’ll be giving you a few tips on impact resistant windows in this post and then hurricane shutters in a post soon to follow.
What Are Impact Resistant Windows?
Hurricane windows are not the same thing as impact resistant windows. Impact windows are what you want if you want your house to have a better chance of surviving a hurricane.
Impact resistant windows are a laminated product. There are two main types or residential impact resistant windows, depending on the degree of impact resistance you are looking for.
One type of window consists of multiple layers of polyvinyl butyral (PRB) sandwiched between two sheets of glass. The glass is then placed in an autoclave at around 400 degrees Fahrenheit under high pressure to temper the glass in order to increase its strength. The PRB type windows are designed for small missile (projectile) impacts.
There are also impact resistant windows designed for larger missile impacts referred to as PET laminated glass and glass-clad polycarbonate. In most cases, the windows are attached to the frame with structural silicone sealant.
Impact resistant windows need to be paired with beefed up frames in order to offer sufficient protection from projectiles. These frames may be constructed of wood, metal, vinyl or a combo of materials and have stiffeners and reinforcement to make them much stronger than typical window frames.
If you are retro-fitting an existing window, it is recommended to replace the entire window system, frame and all, in order for it to work as designed. Securing the window frame to the opening according to the manufacturer’s specifications is key to keeping it intact under hurricane conditions.
Why Should I Install Impact Resistant Windows On My Home?
- Because impact resistant windows have advanced to the point where they are thoroughly tested to withstand Category 5 wind conditions and the debris that goes with it. What that means is that your home has a much better chance of remaining intact with minimal damage.
- If one of your windows falls victim to a chunk of wood flying through it, the air pressure in your home will expand rapidly (much like a balloon) and something will give way. It could be your roof, another window, a door, or even a wall. Once that happens, your home is extremely vulnerable and will quickly deteriorate with each passing minute. Hopefully, you and your loved ones will be out of harm’s way (inland) and not be around to witness the destruction ‘cuz it won’t be a pretty sight.
Are There Any Building Code Standards For Impact-Resistant Windows?
Impact resistant windows must meet certain guidelines in order to be marketed and sold as such. The American Society for Testing & Materials (ASTM) has strict guidelines (E1886 and E1996) for impact resistant windows before it can be certified as impact resistant. In south Florida, for instance, the building code states that all homes constructed after July 2001 must have hurricane shutters or impact resistant glass and window frames for exterior openings in a house to protect against wind-borne debris.
Codes will vary by community, but generally, impact resistant windows must meet these basic guidelines:
- The first test is called a launch missile impact test. A 9-pound 2×4 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.
Here is a 7-second video… "illustrating the testing procedure for a large missile impact test procedure required by ASTM 1886-1996. The window will be cycled thousands of times inward and outward at 1.5 times the design pressure to simulate actual category 5 hurricane conditions before being certified for sale as a hurricane impact window." via engineeringexpress on youtube:
What brands of windows are certified as impact resistant?
As you may have guessed, there are many brands of impact resistant windows available. Most major window manufacturers have impact resistant windows in their product line. Here are just a few:
- Kolbe impact resistant windows
- CGI impact resistant windows and doors
- PGT impact resistant windows
- Astor high impact windows and doors
- Marvin StormPlus impact testing and performance standards
Be sure to look for products certified to meet large missile impact level D, and wind zone 4 testing standards.
Sources and More Info
on Impact Resistant Windows and Hurricane Shutters:
- Florida building codes information on hurricane building codes
- Texas Department of Insurance product evaluation index for impact resistant windows and other building materials
- NOAA’s FAQ section on the hurricane season
- Hurricane shutters FAQ on the NOAA website
- hurricane retrofit guide for windows and doors
- University of Florida information on impact-resistant windows and tempered glass
- Bob Vila on impact resistant windows
- ToolBase Services information about impact-resistant windows
- Window Specs for High Wind Zones
- Read this for even more great info on impact resistant windows.
- Post-hurricane Survival Guide info