What’s the Difference Between Hurricane and Tornado Window Glazing?

06/16/2020

While both natural disasters wreak havoc on buildings, window selection requires different strategies. What’s the difference between hurricane and tornado window glazing? Hurricane glazing is there to protect the building envelop because we assume that people have left the building, while tornado glazing is there to save the lives of people because unexpected severe weather requires they shelter in place.

Ellen Rogers and Drew Vass covered this topic in the May/June 2019 issue of Window + Glass Magazine. Read on for a summary of their findings.

Hurricane Glazing Requirements

Before you can choose the right glazing, you first need to understand what forces windows must withstand. While both hurricanes and tornadoes cause wind damage, it functions in different ways. Hurricane-resistant glazing is designed to protect the inside of a building from high winds, rain, and projectiles. Because a hurricane lasts longer than a tornado, windows need to stay in place during a storm. The main purpose of hurricane window glazing is to resist windborne debris.

The impact test for hurricane glazing is a nine-pound two-by-four shot at 120 mph. Then in addition to standard pressure testing, windows must go through cycle testing measure long-term resistance to flying debris.

Tornado Glazing Requirements

While tornados cause wind damage as well, they are different from hurricanes in that they strike quickly and often without warning. Unlike a hurricane that can last several days, most tornados last less than 10 minutes and strike quickly, without warning.

Tornado testing also includes pressure testing, but the impact test for tornado glazing is a 15-pound two-by-four shot at 100 mph, which is 10 times the amount of load compared to Miami-Dade requirements.

While demand for tornado glazing has been low, since it would be very expensive to achieve testing protocol, the Code Council (ICC) 500 section of the 2015 International Building Code (IBC) – Standard for Design and Construction of Storm Shelters requires buildings in a high-risk area to incorporate tornado-safe rooms into their buildings. This means that many commercial buildings – schools, first responder facilities, and community centers – must comply with the ICC 500-2014 standards. A 2019 Key Media Research Study shows that “impact-resistant applications/products’ was the second-highest trend (of 10) that glass fabricators say will affect their businesses over the next three years.”

Choosing the right glazing

While tornados and hurricanes may seem similar at first glance, there are different considerations when it comes to each. Choosing the right window glazing depends on the building’s use and location. It is important that people are taking refuge behind windows products suited for the storm that they are seeking shelter from. Not sure which is right for your project? Contact us for a quote.