February 26, 2016
by Jennifer A. Morgan, CSI, and Michael Chusid, RA, FCSI, CCS
It is not necessary for most building design and construction professionals to know everything about lightning protection systems (LPS); just the following key points:
1. Risk considerations
Cloud-to-ground lightning occurs in Canada about 2.34 million times a year, including about once every three seconds during the summer months. Lightning is a discharge of static electricity that can send 300 million volts and 30,000 amps through the atmosphere or whatever objects lie in its path between clouds and ground. The burst of energy can trigger fires, cause structural and physical damage, and disrupt electronic and other building services. It also injures or kills 175 Canadians in a typical year. (This data from Environment Canada can be found at www.ec.gc.ca/foudre-lightning/. The site has additional information about lightning and lightning safety, including the Canadian Lightning Danger Map (CLDM) representing areas at greatest risk of being struck by lightning in the next 10 minutes. If storms are forecast or seem imminent, CLDM should be consulted frequently by those engaged in or responsible for outdoor events and activities.)
Lightning-related damage and disruption costs the Canadian economy between $600 million and $1 billion each year. Nearly $40 million of this is allocated to property damage. The Council of Canadian Fire Marshals and Fire Commissioners (CCFMFC) estimates lightning causes around one per cent of building fires. The insurance industry estimates lightning-related property damage claims range in number from 3900 to 5250 per year. The report from which these statistics are extracted summarizes:
The estimated impact of lightning in terms of damage and disruption to Canadians is very large and likely much greater than that attributed to other forms of hazardous weather (i.e. tornadoes, hail, and hurricanes) over the long term.(For more information, see Mills et al’s report, “Assessment of Lightning-related Damage and Disruption in Canada,” published in Natural Hazards.)
Lightning density (frequency/area) is pronounced throughout the lower latitudes from the Maritimes to the eastern slopes of the Rockies and especially in Southern Ontario. Yet, every province is at risk. For example, lightning sparks over half the wildfires in British Columbia. (For more info, visit www.bcwildfire.com/Weather/lightning.htm)
While tornadoes, hurricanes, and floods garner more headlines, lightning is the most frequent weather-related disaster, and vulnerability to lightning is increasing. (Mills [note 2] finds that lightning causes substantial damage in aggregate; however, isolated incidents do not command the kind of media attention given to other types of disasters. As an example, the Category F4 tornado in Edmonton on July 31, 1987 received far more reportage than did the 40,000 lightning strikes scattered throughout Alberta on the same day. A media phenomenon further reducing awareness occurs when many architectural photographers remove air terminals before images are published, thus reducing the public and professions awareness of lightning protection.) According to recent climatological research, global warming could boost the frequency of lightning strikes by 50 per cent. There is also growing recognition that lightning protection contributes to building and community resilience. (See D. Romps et al’s article, “Projected Increase in Lightning Strikes in the United States Due to Global Warming,” from Science in the November 2010 edition. The editor summarizes: “Lightning occurs more frequently when it is hotter than when it is colder. They predict the number of lightning strikes will increase by about 12 per cent for every degree Celsius of rise in global average air temperature.”)
Concurrently, the need for lightning protection is becoming more urgent as buildings are increasingly filled with sensitive electronic devices and systems. The dramatic zigzag bolt from the heavens is the most typical image of lightning. Yet, damage also occurs when arcs leap from one structure into another, and when electrical surges travel for kilometres through power or telephone lines. These remote strikes can fry circuits in computers, appliances, equipment, security systems, light-emitting diode (LED) lighting, electronic door hardware, fire alarms, and other mission-critical devices.
The true extent of this type of damage is underestimated because it is not always associated with lightning. For example, when a major hospital conducted a routine test of a new backup generator it found a nonfunctional circuit board, which was assumed to be a manufacturing defect. The board was replaced but was, again, inoperable at the next routine inspection. Only after several such incidents was the correlation between the failures and thunderstorms realized. No further failures have occurred since an LPS was installed.
Finally, builders should have training and management protocols to protect workers against lightning. This is of particular concern on large sites, since shelter for workers may be located at a distance. The best advice is, “When thunder roars, go indoors.”(See “Lightning Safety on the Job” www.lightningsafety.noaa.gov/job.htm)
2. Professional responsibility
Neither national or provincial building and electrical codes require lightning protection. Instead, the decision to install lightning protection is at the discretion of building owners and their risk management advisors, insurance underwriters, and design professionals. Yet, surveys of architects reveal several Catch-22 challenges. (While not specifically requiring lightning protection per se, several provinces have acts regarding licensing of lightning protection installers and requiring them to conform to CAN/CSA-B72-M1987. Some governmental agencies, including National Defense and Alberta Infrastructure require lightning protection on certain structures. The National Building Code (NBC) suggests (but does not mandate) compliance with the CSA standard. One should consult local authorities having jurisdiction (AHJs) for clarification.)
For example, most architects do not consider lightning protection unless a client asks for it. This is problematic because most building owners rely on their architect to provide professional guidance on technical issues.
An owner’s expectation, in this regard is in line with the Royal Architectural Institute of Canada (RAIC). It states: “Architects serve as trusted advisors… while serving the public interest and addressing health and safety matters.”(Visit https://www.raic.org/raic/what-architect for more information.)
An additional problem arises because most architects assume the electrical engineer will deal with the LPS. Alas, most engineers provide only the grounding and surge protection required for the building’s electric power system, and not for lightning protection.
The architectural stance appears to contradict the RAIC’s statement that:
It is important for the success of your project that the architect—who is uniquely trained and experienced in this regard—be responsible for the overall management of sub-consultants throughout the entire project. This enables the architect to produce well-integrated results by coordinating both the design and administration of the project. (See www.raic.org/raic/how-choose-architect#subconsultants)
An architect should ask himself or herself the following question: “If my client suffers a lightning-related loss, how can I demonstrate I have met the industry’s standard of care?”
Fortunately, a solution to this question is provided in CAN/CSA B72 Appendix A, General Principles of Lightning Protection. (A more detailed risk analysis is in NFPA 780 Annex L, www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=780. An online application for performing calculations based on NFPA 780 Annex L can be accessed online by visiting www.ecle.biz/riskcalculator)
It takes into account a building’s environment, construction type, occupancy, and contents, plus the consequences. The appendix provides a formula for assessing the risk of a lightning damage:
R = (A + B + C + D +E) / F
R = Risk, rated from 0 (light) to over 7 (severe).
A = Structure type, ranging from 1 for small single-family residences to 10 for hospitals, nursing homes, housing for the elderly or handicapped, and buildings containing hazardous materials.
B = Construction type, ranging from 1 through 5, depending on materials used for the structural framework and roof.
C = Relative location, ranging from 1 for small structures near higher structures to 10 for structures extending more than 15 m (50 ft) above adjacent structures or terrain.
D = Topography, ranging from 1 for flat land to 5 for mountain tops.
E = Occupancy and contents, ranging from 1 for noncombustible material in unoccupied buildings to 10 for historic content or explosives.
F = Lightning frequency (annual mean number of days per year with thunderstorms), ranging from an index of 9 for areas with five or fewer days to and index of 5 for areas with 30 to 40 days per year—the maximum expected in Canada.
NFPA cautions that there is need for protection in some cases regardless of the outcome of the risk assessment, including buildings with:
The risks of an unprotected structure should be balanced against the modest cost of installing lightning protection. Roof area is the most significant factor in determining the work required to install lightning protection. This means a multi-storey edifice costs less per square metre of interior floor area than a single storey building would. Costs to install LPS are higher in buildings with extensive rooftop equipment and demanding architectural considerations, and are less in buildings with a modicum of rooftop equipment and a simple configuration. Buildings taller than
25 m (82 ft) are considered Class II structures under CAN/CSA B72 and will incur additional expenses. Understandably, structures such as tall chimneys (Class III) or those housing hazardous occupancies (Classes IV and V) have greater complexity and cost. (A construction cost study, suitable for budgeting LPS in the early stages of project design can be downloaded at www.ecle.biz/coststudy. Based on U.S. construction costs, it must be adjusted based on exchange rates and local market conditions.)
3. Lightning protection systems
The fundamentals of lightning protection have been recognized and improved on for more than 200 years. (In brief, the LPS provides a low-resistance path with adequate capacity for lightning’s electrical charge. Air terminals are placed at locations most likely to be the launching point for a lightning strike. They are interconnected via highly conductive cables that lead to ground electrodes. For additional information, visit www.lightning.org)
CAN/CSA B72 has not been updated in three decades and some subject matter experts advocate the standard has not kept pace with the advances in lightning protection. These experts now recommend that lightning protection meet the following codes in addition to the Canadian standard:
In practice, CAN/CSA B72 is similar to the NFPA, LPI, and UL standards. For optimal protection, however, specifications should require compliance with both sets of standards and that the more stringent clause govern in case of conflicts. (An example of a practice allowed under the Canadian standard but not NFPA is the ‘intercepting conductor.’ This practice omits air terminals and relies on horizontal cables conductors laid directly against roofing to be the contact point for a lightning strike. Many subject matter experts say this practice offers less protection and can result in damage to roofing. On the other hand, the Canadian standard is more restrictive in some regards. It limits the maximum distance between an air terminal and a roof edge to 0.5 m (1.6 ft) instead of 0.6 m (2 ft) as allowed by NFPA.)
Until 2011, the Ontario Lightning Rod Act regulated who could manufacture, install, and inspect lightning protection installations, assigned jurisdiction to the provincial fire marshal, and assured a high level of quality. The act and similar ones in other provinces are now rescinded, making it essential specifiers establish clear quality criteria for their projects. (Regarding a progenitor of the current standard: “In no case has a building rodded under the Lightning Rod Act been destroyed by lightning after having been inspected by the Fire Marshal’s Office.” This comes from Keller, H.C. Keller’s “Results of Modern Lightning Protection in the Province of Ontario,” Farm Paper of the Air.)
The Lightning Protection Institute’s program to certify individuals as Designer Inspectors (DIs) or Master Installer Designers (MIDs) has wide acceptance in the U.S. Until this or a similar system is established in Canada, the design of an LPS is best left to an experienced lightning protection contractor. The designer can be prequalified, or specifications can state requirements such as five years of experience on projects of similar size and complexity within the province.
Lightning protection components should be fabricated to comply with UL96; products fabricated for electric power systems are not sized to handle a lightning strike. A full product line—including clamps, couplings, fasteners, and accessories—requires more than 2000 stock keeping units (SKUs) plus customization capabilities to meet the full range of construction conditions.
The International Association of Electrical Inspectors (IAEI) states, “installation of a lightning protection system is much different from the installation of electrical service wiring.” Installers can be prequalified, or specifications can state requirements such as five years of experience on projects of similar size and complexity within the province. (See Soares Book on Grounding and Bonding, page 444 of the 12th ed. published in 2014.)
While most installers will guarantee their work meets the applicable codes, third-party inspection can be seen as part of the building commissioning process. New Brunswick and Saskatchewan have provincial inspection programs. UL has an inspection program and issues a ‘Master Label Certificate’ or ‘Letter of Findings’ if a project meets their criteria. While not widely used in Canada at this time, there is growing interest in the Lightning Protection Institute-Inspection Program’s Master Installation Certificate.
4. Architectural considerations
Lightning protection is an intrinsic part of a high performance building envelope that mediates between the building’s contents and the powerful forces of nature. Not only is an LPS connected to the roof and walls, but it also figures into the vital interface where the façade meets the roof.
Technically, lightning protection systems have to keep pace with new architectural styles and innovative features—such as earth-covered roofs, rainscreen cladding, and rooftop photovoltaic (PV) collectors—and new strategies are emerging for special facilities such as stadia. (Refer to Joel Kratz and Erik Noble’s article, “Lightning Safety and Large Stadiums,” in the Bulletin of the American Meteorological Society from September 2006. Find it at www.journals.ametsoc.org/doi/pdf/10.1175/BAMS-87-9-1187)
Esthetically, a building owner or designer may be concerned with the visual impact of lightning protection. This concern is understandable as buildings with carelessly placed or poorly maintained lightning protection components distract from the structure’s appearance. The same can be said for anything inelegantly mounted on a building.
However, lightning protection systems can be nearly invisible from normal vantage points and can be installed on most buildings without diminishing the architect’s esthetic vision.
Air terminals are typically slender, short rods that seem to disappear against the sky—especially when installed at the high points of a roof or set back the code-permitted distance from roof edges. While codes specify maximum spacing, air terminals can be set at closer centres to align with building elements.
Creative expression can be given to air terminals as decorative finials in a variety of historical styles or as ornamental glass balls. Additionally, customized air terminals can be built into sculptures or decorative elements and disguised as pennants, spires, or classical acroteria.
At the other end of the conspicuity spectrum, vertical air terminals can be eliminated altogether. Handrails, snow rails, equipment screens, shade canopies, and other building elements can do double duty as strike termination devices if fabricated from metal at least 4.8 mm (3/16 in.) thick and installed with electrical continuity. This technique is increasingly being used in the glass railing systems around rooftop decks, pools, and terraces in highrise buildings. (Strike terminations such as these might be specified in Divisions 05 [metal fabrications], 07 [flashings and roof specialties], 08 [curtain walls], or 12 [sculpture], and require careful co-ordination.)
Down conductors are usually placed inside of new construction. However, with adequate planning, concealed conductors can also be installed inside existing buildings. At a recently retrofitted museum, rooftop conductors entered the building through abandoned roof vents and were bonded to existing structural steel columns connected to ground electrodes; the interior finishes required only minor patching.
When conductors run on exterior surfaces, they should be placed with sensitivity to the architectural design. For example, conductors can run down the ‘back’ side of chimneys, along building edges, behind downspouts, and should be located away from main entrances. Conductors (but not air terminals) can also be painted to match adjacent materials.
5. Specifying and operations
Designers of complex projects may benefit by obtaining guidance from a qualified lightning protection system designer at the early stages of project design. The system designer can be hired by the building owner or architect/engineer (A/E) as a consultant. In this case, detailed lightning protection drawings and specifications are issued as part of the project’s contract documents.
For most projects however, an A/E can prepare a performance specification that delegates the detailed lightning protection design to the contractor. The lightning protection design is then prepared by a qualified individual working for the contractor or sub-contractor. The design documents should state the design complies with specified quality assurance (QA) requirements, be signed by a system designer, and submitted to an A/E as required in project specifications.
With delegated design, the drawings and specifications that are prepared by the project’s A/E do not need to size, detail, or locate lightning protection components or repeat requirements found in the standards. When required, however, contract documents should include optional requirements that affect project esthetics, performance, administration, and co-ordination.
After construction, the building owner or manager should inspect the lightning protection system at regular intervals to ensure visible components are intact and securely mounted. UL inspection certificates expire after three years; a qualified inspector should then be hired to test the system and make necessary repairs so the certification can be renewed.
While damage can occur from vandalism, abuse, or damage to the underlying structure, most problems with LPS are due to building changes. For example, problems can occur when a new pump is installed and not properly bonded to the lightning protection system, or if an air terminal is dislodged during rooftop HVAC maintenance. Building operations staff should be trained to respect its lightning protection systems and appropriate clauses should be included in contracts with vendors working on the building. Some building owners have maintenance agreements with certified installers to be on call.
Reroofing also requires attention. The owner should be consulted before disabling lightning protection in case special procedures are required or the work schedule needs to be adjusted to maintain critical protection. In some instances, existing lightning protection components can be reused if they are determined by a qualified system designer to be in satisfactory condition. Modifications to the lightning protection work should be performed by a qualified lightning protection installer.
The duration of a lightning strike is about 30 microseconds. Fortunately, a properly designed, installed, and maintained lightning protection system can last for the life of a structure. (These authors are certified by the Lightning Safety Alliance to present its continuing education course, “LSA101–Lightning Protection Basics 101.” Visit www.lightningsafetyalliance.com/education.html for more information.)
By observing these guidelines, building owners and the public can enjoy peace of mind knowing lightning protection systems “stand on guard for thee.” (For assistance with this article, the authors wish to thank Scott Simpson of Simpson Lightning Rod [Rockwood, Ont.], Dave Cliff of Dominion Lightning Rod Co. [Dundas, Ont.], Jason Tysick of Burchell Lightning Protection Ltd. [Perth, Ont.], and Simon Larter of Dobbyn Lightning Protection [Calgary].)
Jennifer A. Morgan, CSI, is an officer of East Coast Lightning Equipment Inc., a UL-listed manufacturer of lightning protection components, and an officer of the Lightning Safety Alliance. She can be reached via www.ecle.biz.
Michael Chusid, RA, FCSI, CCS, is an authority on building materials and a consultant to building product manufacturers specializing in product innovation and marketing. He can be reached via www.buildingproduct.guru.
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