Breaking Wind: How Safe is Safe?

Breaking Wind: How Safe is Safe?

If you’re in a mandatory evacuation zone for a hurricane (whether due to winds or flooding), ideally it would be best to relocate outside the affected area. Often, that is not possible, in which case you’ll be relocated to a community shelter. But what makes that shelter any different than your home?

In the U.S., many designated shelters are designed to ensure life-safety protection. The International Code Council (ICC) and National Storm Shelter Association (NSSA) have comprehensive building construction standards that have undergone “missile impact” or debris impact testing: a 9-pound wooden 2″x4″ is fired from a cannon directly at a concrete wall at various speeds up to 0.4 times the simulated hurricane’s maximal wind speed (see images below).

While the ICC-500 standard is most commonly used and often sufficient for storm shelters, the Federal Emergency Management Agency (FEMA) has even more rigorous specifications (P-320/P-361) that provide near-absolute protection against extreme wind events (hurricanes and tornadoes). Spaces designed with the FEMA protocol are termed “safe rooms”, as opposed to shelters, and can withstand multiple direct hits from a 15-pound beam propelled at 100mph.

The Saffir-Simpson Hurricane Scale classifies hurricanes based on the intensity of their sustained winds (not temporary gusts).

• Category 1 (74-95 mph) – Very dangerous winds will produce some damage, but usually cause no significant damage to well-structured permanent homes.
• Category 2 (96-110 mph) – Extremely dangerous winds will cause extensive damage, possibly exposing parts of the roof or damaging poorly constructed doors and windows.
• Category 3 (111-129 mph) – Devastating damage will occur with some structural damage to most small residences and utility buildings, including minor curtainwall failures. Manufactured homes usually sustain severe and irreparable damage. Mobile homes are completely destroyed.
• Category 4 (130-156 mph) – Horrific damage expected, including extensive curtainwall failures and some complete structural failures of small residences.
• Category 5 (>156 mph) – Catastrophic damage will occur. Complete roof and complete building structural failures are common with small utility buildings blown over or away. Heavy irreparable damage or total destruction.

For Hurricane Sandy, parts of New Jersey and New York will anticipate gusts of wind up to 80 mph tomorrow, whereas areas outside the main path may experience wind speeds closer to 50 mph. A total of 6-12″ of rain could fall through Wednesday.

Obviously, a hurricane causes more than just high winds. The majority of people will probably be more concerned with flooding and/or power outages from a tropical storm or Category 1 hurricane.

Stay safe out there. Better to be over-prepared than under-prepared.

Additional info: http://www.fema.gov/

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Image: Wind Science & Engineering Research Center Debris Impact Test Facility in Texas