Lightning protection and the building envelope

Photo courtesy

by Jennifer A. Morgan, CSI, and Michael Chusid, RA, FCSI, CCS
Global warming could increase lightning strikes by 50 percent, according to recently published climatological research. The distribution of lightning activity may also change, raising the occurrence of lightning in regions that heretofore had little risk. At the same time, the need for lightning protection becomes more urgent as buildings are filled with increasingly sensitive electronic devices.

Lightning protection systems can be integrated with new architectural styles and innovative features—such as earth-covered roofs and rooftop photovoltaic (PV) collectors—and new strategies are emerging for special facilities such as stadia. There is also growing recognition that lightning protection contributes to the sustainability and resilience of buildings and communities.

A discharge of static electricity between clouds and earth, lightning can send 300 million volts and 30,000 amps through the atmosphere—or whatever objects lie in its path. The electrical resistance encountered by the burst of energy can trigger fires, cause structural and physical damages, and disrupt electronics and other building services. It can also injure or kill people in or near the structure; lightning is the second most frequent weather-related cause of death.

Property damage from lightning has low probability, but high consequences. Lightning damage in the United States costs over $1 billion annually. The dramatic zigzag bolt from the heavens—causing fires and structural damage—is the most typical image of lightning. Yet, damage can also occur when arcs leap from one structure into another, and when electrical surges travel for miles, through power or telephone lines, and fry circuits in computers, appliances, equipment, building control systems, and light-emitting diode (LED) lighting. These risks should be balanced against the modest cost of installing lightning protection.

2012 Vaisala map
Lightning is not limited to specific locations. More importantly, low flash density does not mean zero exposure to risk. California and Oregon, low-risk states, were among the 14 contiguous states that experienced lightning fatalities in 2013. (National Weather Service). Image courtesy Vaisala

Lightning protection is an intrinsic part of the building envelope that mediates between the building’s contents and the electrical forces of nature. However, a building owner or a project’s architect/engineer (A/E) may be concerned lightning protection will impact the building’s aesthetic. This concern is understandable since everyone has seen buildings with carelessly placed components distracting from the structure’s appearance.

Fortunately, the reality is most lightning protection systems can be nearly invisible from normal vantage points. Air terminals—previously known as ‘lightning rods’—are typically slender, short rods that seem to disappear against the sky. Conductors, the cables that carry current to ground, can be run inside the building or can be detailed to blend into the design. As the case studies in this article demonstrate, lightning protection can be installed on most buildings without diminishing their appearance.

Design and certifications
The fundamentals of lightning protection have been recognized and improved upon for more than 200 years. In the United States, they are codified in standards such as National Fire Protection Association (NFPA) 780, Standard for the Installation of Lightning Protection Systems, and Lightning Protection Institute (LPI) 175, Standard of Practice for the Design, Installation, Inspection of Lightning Protection Systems.

UL standards include:

  • UL 96, Lightning Protection Components;
  • UL 96A, Installation Requirements for Lightning Protection Systems;
  • UL 497, Protectors for Paired-conductor Communications Circuits; and
  • UL 1449, Surge Protective Devices.

Lightning protection systems must comply with industry standards, certifications, and listings to ensure quality of design, fabrication, installation, and inspection.

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