Understanding Hurricane Ratings for Impact Windows

When living in a hurricane-prone area, one of the most crucial decisions you'll make is choosing the right impact windows. How do you know which impact window can protect your home and loved ones during a hurricane?

The effectiveness of impact windows is often indicated by their ratings based on various tests that simulate hurricane conditions.

Large Impact Missile Testing

One way to assess the strength of an impact window is to simulate a hurricane-like event with small and large missiles.

For instance, in Miami-Dade County, impact windows are required by the local code to pass the Missile test to see how the window holds up against flying debris during storms.

During large missile impact tests, 2×4 pieces of lumber are shot out of a steel piping cannon with compressed air at the glass material. The material passes the test if three different samples of the same material withstand the impact of the lumber on two separate surfaces of each glass.

Design Pressure (DP) Rating

Another hurricane rating for impact windows is the Design Pressure (DP). To figure out a window's DP rating, they do tests in three areas:

• Water resistance

• Air resistance

• Handling weight and pressure

The higher the DP rating, the tougher the window is. For example, a window with a DP rating of 50 has been tested to handle around 200 mph winds or 75 pounds per square feet of pressure. 

On the other hand, a window with a DP rating of 35 can manage about 125 mph winds or 50 pounds per square feet of pressure. When your windows confront the fierce might of a hurricane, their ability to withstand the onslaught of wind becomes crucial. 

How to Evaluate Design Pressure Ratings

The Saffir-Simpson Hurricane Wind Scale classifies hurricanes in the following format:

• Category 1: 74-95 mph

• Category 2: 96-110 mph

• Category 3: 111-129 mph

• Category 4: 130-156 mph

• Category 5: 157+ mph

You can imagine every 10 points in the DP rating as the equivalent of a hurricane level. So, an impact window with a DP rating of 200 should be able to survive a Category 2 hurricane, a DP rating of 30 should withstand a Category 3 hurricane, and so on.

Performance Grade Rating

This rates how well a window can handle hurricane-like winds, usually scoring between 15 and 70. A higher PG means it can handle strong winds and debris better while keeping water and air out. 

Most impact windows typically have PG ratings between 15 and 70, with the numbers directly correlating with the extent of wind pressure the window can handle. For instance, a window with a PG rating of 35 can handle 35 pounds per square foot pressure.

The PG rating is newer than the DP rating and has stricter requirements. As this rating system is more recent, it better reflects an impact window's performance than the DP rating.

Visible Transmittance (VT)

Impact windows don't have to be crystal clear. A low VT means less light comes through, providing more privacy and making it harder for burglars to see inside.

Solar Heat Gain Coefficient (SHGC)

This measures how much sun heat a window lets in. A low SHGC means less heat enters your home, keeping it cooler during hot weather. Low numbers like .30 to .60 mean the window effectively repels solar radiation. It is ideal for homeowners in coastal areas like Florida who want to keep indoors cooler.

Why Do Windows Have Different Ratings?

Just as everyone has unique tastes, homeowners have reasons for choosing specific windows. Someone living in a hurricane-prone area might need impact-resistant windows for safety.

Meanwhile, another homeowner might be keen on impact windows to make their place more energy efficient. These differences in needs explain why there are various window ratings. They're there to help folks find the right window that matches what they want and suits the demands of their area.

Safeguard Your Home With Highly-Rated Impact Windows in Miami and Broward!

We offer a range of high-quality impact windows designed to withstand hurricanes and other forces of nature. Our windows have high hurricane ratings, ensuring superior protection for your home and family. Call us today to explore our wide selection of impact windows.