Assessing Wind Vulnerability

How to assess wind vulnerability of critical facilities' roof systems

Editor's note: The following article is adapted with permission from the American Society of Civil Engineers (ASCE) from a peer-reviewed paper, "Wind Vulnerability Assessment of Roof Systems and Rooftop Equipment for Critical Facilities: A Preliminary Protocol for Design Professionals," presented at ASCE's April 2011 Structures Congress.

Roof systems and rooftop equipment are key building components that frequently are damaged during high winds. These components' wind vulnerability depends on various factors, including adequacy of their design and installation and material degradation over time. Leakage from damaged roofs or rooftop equipment has interrupted numerous facility operations, and many critical facilities, such as emergency operations centers, fire and police stations, hospitals, nursing homes, power plants, schools and other buildings that are essential for delivering vital services or protecting a community, have been forced to evacuate occupants because of roof leakage.

By identifying wind vulnerabilities, mitigation efforts can be undertaken to avoid future damage and disruption of services provided by critical facilities. Design professionals can use the following preliminary protocol to systematically guide their assessments of roof systems and rooftop equipment.

FEMA P-424, "Design Guide for Improving School Safety in Earthquakes, Floods, and High Winds"; FEMA P-543, "Design Guide for Improving Critical Facility Safety from Flooding and High Winds"; and FEMA P-577, "Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds" recommend performing a vulnerability assessment on all critical facilities older than five years. If a facility is located in a hurricane-prone region (as defined in ASCE 7-10, "Minimum Design Loads for Buildings and Other Structures"), the assessment is recommended regardless of building age. These publications note it is particularly important to perform assessments on facilities located in hurricane- and tornado-prone regions.