Lightning protection code changes improve safety and resilience

by maz_atta | April 14, 2021 12:00 pm

Jennifer Morgan, CSI, and Michael Chusid, RA, FCSI, CDT

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The 2020 edition of the Canadian Standards Association (CSA) B72:20, Installation Code For Lightning Protection Systems, is a significant overhaul of the previous, 1987 version. According to Simon Larter of Dobbyn Lightning Protection, chair of the CSA committee responsible for writing the new edition, “This is the first revision to the document in over 30 years and marks a major step forward for the Canadian lightning protection industry. A quick look…shows a vastly changed code, boasting much greater applicability and clarity. Requirements that users previously found confusing and conflicting have been removed and the regulatory loopholes have been eliminated. In their place is a fully updated standard complying with CSA’s latest style manual, and streamlined for ease of use and installability.”

Larter explains, “Major changes include harmonization of the requirements with those of the U.S. lightning protection standard (the National Fire Protection Association [NFPA] 780, Standard for the Installation of Lightning Protection Systems), an added chapter on protection for solar arrays, and a new lightning risk evaluation method. Guidance has been added for several specialized structure types, including structural steel buildings, telecommunications equipment, rooftop helipads, and fabric structures. The document now gives authorities having jurisdiction (AHJs) and design professionals more comprehensive information from which decisions regarding lightning protection can be derived.”

The updated requirements, as they are incorporated by reference into the National Building Code (NBC) §s3.6.1.3 and other codes and standards, “will dramatically increase the quality and safety of lightning protection systems country-wide,” according to Larter.

This will have an obvious and immediate impact on the work of lightning protection system (LPS) designers and installers. Additionally, architects, engineers, and property managers and owners will benefit from increased clarity when drafting lightning protection project specifications. This, in turn, should lead to increased protection of buildings and their contents from lightning damage.

Bringing it down to earth

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Lightning is one of the most frequent, violent, and destructive forces of nature. Yet, individual incidents seldom generate the type of widespread attention garnered by meteorological events that affect a broad region, such as floods or blizzards. A reading of headlines from across Canada reveals significant havoc is caused by lightning on a regular basis. (See “Lightning Damage Case Studies”, page 24.)

To determine which buildings are most vulnerable to lightning damage, a risk assessment guide is included in Annex C – Determining the Need for Protection of CSA B72:20. Lightning protection should be provided for a structure if the threat exceeds the tolerable threshold.

Factors contributing to the lightning threat determination include:

• ground flash density – the frequency of lightning strikes in various parts of the country;
• equivalent collection area – taller and bigger structures provide a larger “target” for lightning; and
• location factor – isolated, tall, and elevated structures are at greater risk than are those that are surrounded by taller buildings.

Tolerable lightning frequency is based on:

• construction – buildings with combustible structural systems and roofs have less tolerance than are those with noncombustible and conductive materials;
• contents – buildings with valuable or hazardous contents have less tolerance than those with lower value;
• occupancy – buildings that are difficult to evacuate have less tolerance than other structures; and
• consequences – structures that are required to provide continuity of service have less tolerance, structures where a lightning strike could have dangerous consequences to the environment have a much lower tolerance.

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An easy-to-use, online lightning risk calculator that considers these factors and produces a risk report for a specific structure is available without cost at www.bit.ly/LightningRisk. While this tool can be used with new construction or existing buildings, it is most advantageous to conduct the lightning risk assessment early in the design process.

There are applications for which an LPS should be considered regardless of the outcome of the risk assessment. These include factors such as:

• the presence of large crowds, where continuity of critical services is required (e.g. hospitals and power generating stations);
• facilities containing explosive or flammable materials; and
• sites of irreplaceable cultural heritage.

Additionally, LPS is required for most military and nuclear construction, and many AHJs (e.g. Alberta Infrastructure and SaskPower) frequently require lightning risk assessments.

CSA B72:20 cautions:

“Lightning can result in indirect losses that sometimes accompany the destruction or damage to buildings and their contents. An interruption to business… can involve losses quite distinct from and additional to the losses arising from the direct destruction of material property. There are cases where whole communities depend on the integrity of a single structure for their safety and comfort… A stroke of lightning to the unprotected chimney of a pumping plant, for example, can result in a serious shortage of sanitary drinking water, irrigation water, or water for fire protection.” (§C.7)

If lightning protection is required

“The function of a lightning protection system is to provide a means by which a lightning discharge can enter or leave the earth while eliminating or minimizing damage to the structure on which the system is installed,” as succinctly stated by CSA B72:20 (§0.1).

An LPS does this by providing a low-impedance path to safely conduct lightning through a building, between earth and the atmosphere. The path includes:

• strike termination devices (such as air terminals, also known as lightning rods) and conductors on the roof and other elevated locations;
• grounding electrodes;
• a conductor system connecting the roof-level and ground-level systems by means of down conductors;
• interconnecting conductors to provide equipotential bonding connections throughout metallic building elements and systems; and
• surge protective devices on power, communication, and data lines penetrating the building envelope.

A fuller discussion about LPS elements and system design is in the authors’ previous paper, “Lightning Protection: Five Concepts you Need to Understand,” in the March 2016 issue of Construction Canada.[4] The Lightning Safety Alliance[5], in conjunction with lightning protection professionals across the nation, also provides continuing education classes.

Most of the revisions to CSA B72:20 will not be noticeable in the field except by experts. However, the following changes will be apparent to most construction industry professionals walking a jobsite.

Prior to the update, intercepting conductors could be installed on parapets and roof ridges without the benefit of air terminals. As a result, lightning strikes were apt to perforate parapet caps and roofing materials. Air terminals are now required in those locations.

Air terminals must now project a minimum of 254 mm (10 in.) above what they protect; an increase from the previous requirement of 50 mm (2 in.).

Rooftop equipment was previously permitted to be simply bonded to the main lightning conductor. Now, rooftop units must be provided with air terminals and conductors if they are not in a zone of protection offered by lightning protection installed on higher elements of the structure.

Standard electrical conductor (e.g. No.2, #2/0) was previously permitted to be used in an LPS. In the new edition, only conductors and components labeled specifically for lightning protection may be used.

The recommendation against sharp bends in conductors did not define any limits. Now, bends must have a 200 mm (9 in.) minimum radius.

Copper components are no longer permitted in contact with steel or galvanized steel. Instead, aluminum is required in these locations to prevent galvanic corrosion.

Another important distinction is that CSA B72:20, “does not cover installation requirements for early streamer emissions systems or charge dissipateon/charge transfer systems. No recognized standards body or testing agency exists for Canadian installation of these devices.” (§1.3)

A new tune

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While CSA B72 has been harmonized with other North American standards, each document has notes that are necessary to complete the melody. Therefore, the authors recommend a project specification also reference the following:

• Lightning Protection Institute (LPI) 175, Standard of Practice for the Design – Installation – Inspection of Lightning Protection Systems;
• NFPA 70, Installation of Lightning Protection Systems; and
• the Underwriters Laboratories (UL) 96A, Installation Requirements for Lightning Protection Systems.

Taken together, these standards cover almost every condition encountered in conventional buildings. For example:

• NFPA limits, with regards to wind resistance, the size of ornaments installed on air terminals, a topic unaddressed in CSA B72;
• CSA B72 permits rooftop railings as thin as 3.2 mm (126 mils) to be used as strike termination devices, while UL 96A makes clear this also applies to rooftop ladders; and
• NFPA provides extensive guidance on lightning surge protection, while CSA B72 offers only a short, non-normative annex on the subject.

In addition to codes and standards, the lightning protection industry is supported by organizations that certify individuals working in the industry and the quality of installations. As Larter explains that building, “designers should ensure lightning protection is installed by experienced, qualified firms with a demonstrable record of providing certified systems.”

The Lightning Protection Institute[7] (LPI) has testing and certification programs to qualify lightning protection installers and designers. Additionally, the Lightning Protection Institute – Inspection Program (LPI-IP) performs third-party inspections and certifications of individual LPS installations. More information about these certifications is in the aforementioned article in Construction Canada.

Specifiers can rely on these codes, standards, and certifications as the basis for delegating LPS design. A project specification should require LPS to comply with the four codes and standards, the design to be prepared by an LPI-certified Master Installer or Master Installer/Designer, the installation to be performed by a firm with requisite experience and an LPI-certified Master Installer, and that the installation be inspected and certified by LPI-IP.[8]³

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By delegating design, it is not typically necessary to draw or detail LPS in contract documents. Drawings, however, should indicate the scope of the lightning protection if there are multiple structures onsite. They may also be necessary to explain special esthetic requirements, such as the alignment of air terminals with certain façade features or the use of metal fabrications as strike termination devices in lieu of air terminals.

Specifiers need note the latest edition of MasterFormat—the CSC and CSI standard for organizing construction activities by work results—has created new section numbers and titles for lightning protection of buildings, including:

• 01 56 21 – Temporary Lightning Protection;
• 13 01 46 – Maintenance of Lightning Protection; and
• 13 46 00 – Lightning Protection Systems.

Lightning protection was in Division 13 – Special Construction prior to being moved to Division 26 – Electrical in the major revision of MasterFormat in 2004. Restoring it to Division 13 underscores:

• an LPS is integrated with many other systems in a building; and
• while lightning protection services are frequently subcontracted through electrical contractors, the requirements for and components of an LPS are much different than those that apply to building power systems.

Ongoing developments

The revised code says, “Liability for the safety of occupants from lightning has become an increasingly important factor owing to stricter safety practices enacted by provincial and federal agencies.” (§C.3)

More, design professionals and property owners have a moral and common law liability to protect the health, safety, and welfare of buildings and the public.

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The need for lightning protection has grown due to increasing reliance on electronic controls to operate buildings and the quantity of sensitive electronic equipment housed within structures. Even if there is no structural damage from a lightning strike, the powerful surge induced by lightning can create costly damage to electronic circuits in unprotected facilities.

Finally, changes in the frequency and distribution of lightning strikes, has been driven home by a summer of lightning-spawned destruction. Firefighters from Québec were deployed in California to help contain so called “lightning complex fires” that had already destroyed an estimated 14,000 km² (5405 mi²) of wildlands by the time this manuscript was submitted. British Columbia recorded 1600 lightning strikes in a single weekend in August 2020. In Northwest Territories, researchers allege lightning-caused fires rose by two to five per cent a year for the last four decades. While claims like this are still subject to scientific debate, and data on the changing characteristics of strikes to buildings is being gathered and analyzed, it has become increasingly prudent to consider LPS as part of building and community resiliency.

The revised code represents the product of extensive scientific research, field experience, and codification. Much of the early work demonstrating the value of LPS was conducted in Canada. For example, Ontario’s Lightning Rod Act became effective in 1922 and subsequent studies proved properly designed and installed lightning protection systems were invaluable in preventing structural fires. With the new code, Canada once again moves to the forefront of the art and science of effective lightning protection.

[11]Jennifer Morgan, CSI, is with East Coast Lightning Equipment, Inc. (ECLE), the leading North American producer of components for lightning protection systems. She is also an officer of the Lightning Safety Alliance. She can be reached through www.ecle.biz.

 

[12]Michael Chusid, RA, FCSI, CDT, provides technical and marketing support for building material manufacturers and can be reached through www.chusid.com.

Source URL: https://www.constructioncanada.net/changes-to-lightning-protection-code-changes-improve-safety-and-resilience/

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