By JACK J. MURPHY and JIM TIDWELL
The green movement in the United States is a serious effort to minimize and even reverse the damage being done to our planet. The federal government has implemented dozens of programs to provide incentives to individuals and businesses to conserve energy and reduce their negative environmental impact. Energy conservation is the area of activity that has garnered the most attention. With declining levels of fossil fuels, increasing costs, and the rise in global temperature, almost everyone agrees that we need to conserve energy wherever possible. The green movement doesn’t stop with energy consumption in buildings; it also encourages recycling building materials and waste and water conservation.
GREEN CONSTRUCTION AND ITS COMPONENTS
Green construction creates sustainable, high-performance structures that integrate and optimize all major high-performance building attributes such as energy efficiency, durability, life cycle performance, and occupant productivity. This holistic approach to design, construction, and demolition minimizes the building’s negative environmental impact; is environmentally responsible; and is resource efficient throughout the building’s life cycle, from the site design to construction, operation, maintenance, and deconstruction.
SITE AND LANDSCAPE ISSUES
A site’s selection and use have greater potential to affect a fire department’s ability to provide service to a green building’s occupants than any other factors. In the past, prescriptive code requirements for fire department vehicles and personnel access were considered reasonable. However, with a focus on walkable communities, urban villages, ecological designs, and so on, these prescriptive requirements are being challenged, and performance criteria are needed to better serve the public.
Firefighters must have access to sites and buildings to provide emergency services. To develop a sustainable site, the amount of ground covered by impermeable materials such as asphalt must be minimized. The fire service may be more comfortable with paved roads, driveways, and fire lanes, but aggregate open-grid pavers and permeable concrete, which can be engineered as all-weather surfaces, will also support the weight of a fire apparatus. Marking these types of accessways may be challenging, but there are many ways to do so.
| (1) Although awnings and trees provide shade for green buildings, they may hinder roof access. (Photos by authors.) |
It’s likely that a developer will want streets narrower than normal fire lanes. He may desire traffic-calming devices such as speed humps, and he may plan landscaping and benches where streets or access roads would usually be. Fire department vehicle access is a public safety requirement, and some ideas that can merge the developer’s goals with fire department access needs include roll-down curbs, drivable sidewalks, and other innovative ways to get fire apparatus to their destination.
A planned large walkable community may severely limit firefighter access to a building’s interior spaces. In this case, consider providing firefighting resources within the facility. Standpipes are an obvious choice, but other novel features might include firefighter staging areas such as pressurized rooms with substantial passive fire protection; they may contain a cache of fire equipment and a standpipe connection. Landscaping can also encourage fire spread if this isn’t considered during the planning stages. In areas subject to wildland fires, the issue becomes even more important.
BUILDING ENVELOPE
The design and construction of a building’s exterior will significantly impact its ability to conserve energy—one of the hallmarks of green construction. Other factors such as natural lighting, recycling, and overall environmental stewardship will also be considered. Enhanced insulation products and techniques, high-performance glazing, and vegetative roofs are a few of the shell components that contribute to sustainability. Although some have little or no effect on fire safety, others present significant challenges, which include the following.
Insulation. As insulation techniques and products evolve, a reasonable level of fire safety must be ensured. Most foam insulation products coming to the market are either polyurethane or expanded polystyrene foam, both of which are manufactured from petroleum derivatives. Untreated and exposed to elevated temperatures or flame, these foam products will burn vigorously, producing copious quantities of smoke and spreading fire to other combustibles.
Most foam insulation materials are closed cell foams, which are either rigid or softer cells. As long as fire doesn’t reach the foam core, they are as safe as any other building component. Depending on the foam level of flame retardant, however, it’s possible that a fire could consume the entire foam core, leaving only the encasing material to withstand the structure’s gravity.
The burning characteristics of foam insulation are such that any installation instructions, listing criteria, or design instructions must be followed very carefully. Failure to design and install a product in strict compliance with its listing could increase the foam’s ignition hazards and fire spread potential, which could have disastrous results.
Fire department concerns with insulation include the following:
• Exterior facades of foam may not be structurally sound and can be easily mistaken for stone or other solid materials. A firefighter should be aware that applying a load to a foam component of a building’s façade, such as his own weight, may cause it to fail. Do not expect foam to carry any load. Do not place ladders, firefighters, or their gear on foam core outcroppings of buildings or other façade components that might fail under load. Buildings under construction may not have completed all of the required protection schemes for foam insulation material, and a partial exterior application may burn profusely. These fires are spectacular and have the ability to spread to interior rooms through windows and other openings.
Vegetative roof system. A vegetative roof system is a top layer of living plant materials and soil known as growth media or engineered soil and is supported on the roofing assembly below. There are three categories of vegetative roof systems: extensive, intensive, and simple intensive. Each type is defined by the depth of the growth media layer and the kind of vegetation.
The extensive green roof system is the most common vegetative roof system and consists of a growth medium (soil) less than six inches deep and three to four inches wide. It requires minimal maintenance once the vegetation has become well established (usually after two or three growing seasons). Typical vegetation consists of low-growing, nonwoody plants including succulents, mosses, and grasses. These ideal plants have tolerance to drought and temperature extremes, exhibit good growth and survival rates, and have a strong horizontal root system that is a nonaggressive vertical root system.
| (2) Growth media on a roof may hinder truck operations for ventilation. |
Fire department concerns regarding vegetated roof systems include the following:
• Roof load. The loads applied to a green roof will be substantially different from those applied to a traditional roof. The type of growing medium and plants will add considerably to the load, and if the roof is intended for social gatherings, that load will also need to be calculated. When calculating the roof load, include the complete saturation of the growing media. Many green roofs include stone or concrete pavers, which may not show up on preliminary drawings but must be included in load calculations. Wind uplift pressures and wind loads should be included in the process. Avoid any roofing material or objects placed on the roof that might become flying debris.
• Roof drainage. Adding plants and a growing medium to the roof can radically change a traditional roof’s water retention characteristics and thus its drainage characteristics. Also, make arrangements to prevent roof drains from being obstructed by growing medium or other material from the planted roof.
• Roof slope. Green roofs, unlike traditional roofs, have increased slopes that may require additional engineering to keep the growing medium and plants from shifting during heavy rain.
• Roof access. A clear space around the roof’s perimeter should be made wide enough to accommodate firefighters with equipment. In addition, pathways should be provided so that firefighters can access rooftop equipment, skylights, and other areas to perform vertical ventilation.
• Supporting structures. Support may be either concrete or steel, so long as all of the loads are considered. One potentially overlooked consideration is the corrosion resistance of any anchors, fasteners, or roof components. Some corrosion-resistant treatments perform differently under conditions where they are constantly wet or damp, as opposed to being in a wet/dry cycle.
• Fire exposure. Although there are no current ratings for green roofs, FM Global Insurance has suggested that green roofs be considered similar to traditional roofs with regard to exposure from an interior fire. If the roof is metal deck, it is considered Class I or II; if it’s concrete deck, it will be considered noncombustible. When considering exterior fire exposure, a careful evaluation is necessary. Consider this hazard when selecting plants and other rooftop materials. Plants with a high moisture content, low growing succulents, and similar plants will enhance the roof’s fire performance, assuming they’re maintained. Avoid plants with high levels of volatile oils or resins, especially in areas prone to wildland fires.
• Parapets. To avoid losing a growing medium and to provide safety for anyone below a green roof, consider providing a parapet along the roof’s perimeter. It should be tall enough to ensure that it will contain any material that is subject to floating off the roof during harsh weather.
• Wind-speed restrictions for green roof systems can apply to geographical locations where the basic wind speed (three-second gust) is determined and does not exceed 100 miles per hour (mph); this applies to all building heights. Area wind uplift pressures, wind rating pressures, and wind loads need to be designed and calculated for safety factor based on a dry condition (no water present in the growth media, retention mat, drainage panel, and so on) and without the presence of a vegetation load. Green roof windborne debris from wind uplift pressure may be a problem if the roof is not designed to meet wind specification of the area.
High-performance glazing.Sustainable buildings depend a great deal on natural lighting to create the interior environment desired and to save on artificial lighting. Therefore, windows become important because of the potential energy loss resulting from heat transfer between the building’s interior and exterior.
Fire department concerns with high-performance glazing include the following:
• Some glazing systems make it extremely difficult to break a window for ventilation or rescue purposes. For security purposes, a blast-resistant film is often applied to glazing, making it virtually impossible to penetrate with normal tools. Consider inserting breakout panels similar to those required in high-rise buildings. These panels should be clearly identified so that, in case of emergency, firefighters can use them for entry or ventilation.
Building design attributes.There are many methods for altering a building’s energy use and other consumables through design techniques. For instance, the building’s orientation to the sun will affect heating and cooling needs; constructing the building to take advantage of natural light will reduce the need for artificial lighting, and eliminating alcoves and similar spaces on the building’s exterior will enhance security without requiring additional lighting.
One of the more relevant design attributes to fire safety is the use of large, open spaces. This style of building has grown in popularity for a number of reasons, mostly because it provides an opportunity to use more natural lighting, provides fewer barriers to air movement for a greater heating/cooling efficiency, and creates an overall feeling of openness for the occupants. From a fire safety perspective, these large open spaces can promote faster fire growth because of the greater volume of air and the more readily available fuel sources. This type of design also creates a lack of compartmentation, which limits fire spread to a smaller area such as a room, a wing, or a building floor.
Most building fires are ventilation controlled—that is, the size of the fire is controlled by the availability of oxygen. In many room fires, the lack of oxygen stymies fire growth until someone (many times a firefighter) opens a door or window to allow for additional oxygen.
When designers begin using large open spaces in commercial buildings, some code provisions may come into play. For instance, atria, because of their large volume of open space, require additional protection by building and fire codes, which could include automatic sprinklers, fire alarm systems, smoke control systems, passive fire protection, and fire safety and evacuation planning.
In homes constructed to residential codes, no such recognition exists, possibly because residences are perceived to be smaller and less hazardous than commercial buildings. From a fire safety and fire suppression perspective, however, the occupancy is less important than the building. Take caution when working a fire in a residence with large open spaces. The span of support beams is longer, and the ceilings are taller, representing a far greater risk of collapse, which will likely be considerably larger, resulting in entrapment of the firefighters working in the space.
Fire department concerns with building design include the following:
• Ventilation-controlled fires will no longer be the norm, as the large open spaces will provide all the ventilation necessary to consume all combustibles in a building. A department’s fireground strategies and tactics should consider controlling ventilation using positive-pressure techniques or otherwise directing the airflow. Also, firefighters should be aware of the building’s fuel load and make appropriate plans to control a free-burning fire that may not have vented to the exterior.
• Large open spaces require long spans of support beams. Lightweight construction with long spans in large spaces will contribute to early structural failure in these buildings.
• Where atria use automatically controlled windows to contribute to energy conservation, their controls should be integrated with the fire alarm system and the smoke management system and provide manual control to the fire department during firefighting operations. It’s likely that, without full building system integration, some of these features will contribute to fire spread and interfere with fire department emergency operations.
Water conservation.Two green community water techniques deserve our attention: rainwater collection systems and gray water systems. Rainwater collection systems collect water for landscape irrigation and other uses that don’t require significant treatment. If the collection vessels are on or under the ground, they don’t pose a problem for the fire service as long as they don’t inhibit firefighter access. However, if rainwater is collected and stored on rooftops or on upper floors of buildings, they add a significant structural load, which must be addressed. Although new construction is relatively easy, design engineers simply calculate the additional load when designing the structure. Retrofitting a collection system on existing buildings poses a far more difficult problem. These additional loads must be considered during the installation of these water conservation systems, including the containment vessels, piping, and collection systems.
| (3) Exterior photovoltaic panel inverters. |
Gray water is typically recognized as a source of potentially recycled water that has been used but not polluted. This normally comes from bathing, washing, and similar activities. Gray water can be collected and reused for landscape irrigation and other uses that don’t require potable water. One current reuse method uses warm gray water to heat water in piping systems through something akin to a heat exchanger. These systems pose a different potential problem for the fire service.
Fire department concerns regarding water conservation include the following:
• Underground rainwater cisterns may not be identified. Driving over one of them could collapse the cistern cover and disable a fire apparatus.
• Added loads to structures may result in early, violent collapse. It’s critical to consider “point loading” of a roof or floor system by the addition of water tanks.
• If gray water is used, it’s possible that firefighters could be exposed to unknown biological hazards. Carefully investigate the gray water’s makeup prior to any emergency operations in the building. Gray water, at this time, is not recommended for use in the water supply for a sprinkler system.
BUILDING SYSTEMS
Alternative power systems. There are a number of alternative power systems on the market. The two most common are photovoltaic (PV) systems and wind-power generators (wind turbines). Both systems generate direct current (DC) power, which must be converted to alternating current (AC) for use in buildings. Although wind turbines and PV systems have a lot in common, it’s necessary to consider each separately to ensure all of the hazards are considered.
PV solar panels. The fire service can be sure that it will have at least one emergency involving a building with a PV solar panel system. PV power is an array of cells that contain a solar PV material, which converts solar radiation into DC electricity. Solar cells produce the DC electricity from sunlight, which can be used to power equipment or to recharge a battery. These modules are used for grid-connected power generation that uses an inverter to convert the DC to AC. A solar cell requires protection from the environment and is usually packaged tightly behind a glass sheet. The PV panel construction should be tested as an assembly to meet the same fire rating as the roof it’s being mounted on.
PV works best when the sun is shining, although power may be generated if any light is available to the panel. Most PV modules and installations are ground mounted or built into the building’s roof or walls. In a PV emergency, firefighters must be aware of potential dangers and hazards. The obvious dangers are electric shock, inhalation from module chemicals used in manufacturing solar panels, and tripping hazards when panels are installed on rooftops.
Fire department concerns with PV systems include the following:
• Power shutoffs. There may be several places to shut off PV system power. However, the safest shutdown point is at the PV panel itself. Although current technology would make this arrangement easily achievable, no manufacturer has done so. This leaves the next best location for shutdown at the inverter; this is a fairly standard design. The system should be designed to automatically shut off power to the building’s electrical system should the inverter lose power from the power company’s grid. This would enable firefighters to terminate power at the inverter by using routine power-cutting techniques. If this is accomplished, the next consideration is the inverter’s location. For fire suppression purposes, the inverter should be as close to the solar-generating devices as possible because the wiring between the generating device and the inverter will always be energized. Microinverters are now available, individually controlling each solar array. Installation of these devices will typically be in close proximity to the array they control and are preferable to any other arrangement currently available. If a system is very small and doesn’t have the appropriate shutoffs, reduce or eliminate power generation by covering the panels with a dark-colored tarp or other material that effectively eliminates any light reaching the panels. This is not the best choice and may not immediately reduce the power generation to zero, but in an emergency, consider all options.
• Marking/labeling. Clearly marking a building that has any alternative power source is important to firefighters. This marking should be at a noticeable location, usually at the building’s power feed. Power shutoff locations should be indicated and marked accordingly. Any components and wiring should be labeled including wiring that will remain energized after normal power is shut off. All markings should consist of materials that will withstand the elements. Also, trip hazards should be identified and marked for firefighters working on a roof in a smoky environment.
• Roof ratings. All PV cells should be tested and listed by a recognized testing laboratory. Their fire resistance should be at least as robust as the roof they’re being mounted on to comply with most building and fire codes. It’s possible, even likely, that installation of a PV array on a roof will change the way the roof reacts under fire conditions. This is caused by the proximity of the panels to the roof, resulting in thermal feedback and the wind tunnel effect between the panel and the roof that can be achieved under certain conditions. Wherever possible, avoid placing firefighters on rooftops, especially where solar panels are installed.
• Roof access for ventilation. Placing a solar panel or two on the roof of a building won’t normally create a significant problem for roof ventilation. However, if much of the roof is covered, the problem becomes severe unless this concern is addressed during the planning stages. Consider providing access routes and ventilation points on roofs with these systems. Pathways on a residential pitched roof, where panels are located, should be at least three feet wide and on the ridge line or hip for support. On commercial flat roofs, the pathway should be at least six feet wide and on all edges of the roof, and ventilation points should be provided every 150 feet in a matrix or similar pattern on the roof. Always provide pathways over robust structural members. Even with this configuration, firefighter safety concerns may dictate a command decision on the fireground that roof ventilation is not worth the risk, and to use alternative tactics.
• Roof loading. For new systems, the additional load of solar panels should be considered when developing the building’s structural design. For retrofit applications, it is critical to ensure the roof system has the carrying capacity for the panels and will withstand any additional loads, such as wind loads, especially in areas subject to hurricanes and similar weather events.
• Fire. If a fire occurs within a solar array, it should be treated like any other energized equipment. Never assume that the fire has affected the power-generating capacity; always consider all circuits energized. If a fire occurs in a building supplied by an alternative power source, verify power shutdown prior to operating within the structure.
Wind turbine systems.Wind farm turbines are used for commercial production of electric power and are usually three-bladed and pointed into the wind by computer-controlled motors. These turbines have speeds of more than 200 mph and are highly efficient and reliable. The blades are usually colored light gray so they blend in with the clouds. They range from 65 to 130 feet or more in length. The tubular steel towers can range from 200 to 300 feet tall. At the highest rotation tip, speeds can exceed 300 feet per second. A gear box is commonly used to step up the generator’s speed.
All turbines are equipped with shutdown features to avoid high-speed wind damage. Wind turbines on buildings present similar issues as any other applied live load. The building must be able to withstand not only the device’s weight and peripheral equipment but also the forces of wind against the blades and any forces exerted by the blades’ rotation. Whether the wind generator is mounted on a stand-alone tower or the building, the electrical system is the same and very similar to the systems used for PV systems. The wind generator sends DC electricity to an inverter—converting the power to AC—and synchronizes the sine wave, voltage, and amperage with the traditional power source for the building. As with PV systems, any power loss from the primary power source should automatically shut off power coming from the inverter.
(4) Hazards associated with solar array panels include electric shocks and tripping. |
Hydrogen fuel cell power systems. The fuel of choice for modern fuel cells is hydrogen. Hydrogen fuel cells are somewhat more technologically advanced than the battery in your car; they use both hydrogen and oxygen to generate electricity, and their by-product is water. They are considerably larger than a typical automobile fuel tank. And, as with any new technology, there are many issues to work through before they become viable for any particular application. Regardless, they are currently available and in use around the country.
Hydrogen fuel cells have their advantages and disadvantages. Storing hydrogen on site provides pure, available hydrogen to the fuel cell. It’s a simpler installation, as there is no separator to manage and the quality and quantity of the fuel are known. The downside of this is that hydrogen is considered a dangerous gas; it has the widest flammable range of any gas, thus making it more prone to accidental ignition than any other fuel.
Hydrogen fuel cell generators are likely to become much more prevalent. Whether it’s a fuel cell uninterruptible power system (UPS) for a desktop computer or a large hydrogen fuel cell-powered generator for a large campus, emergency responders need to be ready. The fire service should be alert to new installations and replacement of generators; determine if any are using natural gas or on site hydrogen storage, and plan accordingly. Gas detection with automatic shutdown and storage site security should be considered for any installation.
Battery storage systems. Batteries can be used in all types of systems, including PV, wind-power systems using turbines, hydroelectric generators, hybrid renewable energy systems, and other redundant power sources.
A battery system typically serves the following two purposes:
• To store power from the grid or a generating source (PV, wind generators, and so on) to be used when the normal source of power becomes unavailable.
• To filter the power coming into the building’s internal power grid. Routing all power through a battery system effectively removes all of the variances that could damage electrical equipment within a building.
Several types of batteries can make up one of these systems. Lead acid batteries are the most common because the overall cost is lower than other types. They generate hydrogen gas in relatively small quantities as they are charged; these systems must be in well-ventilated rooms.
Another concern to firefighters is the electrolyte used in these batteries—sulfuric acid. As long as the acid is contained within the battery, it presents no significant threat. However, if the battery is damaged from fire or mechanical action, the acid is highly corrosive and toxic. Other batteries using similar technology are commonly called gel-cell batteries. These batteries use the same technology, but the electrolyte has silica suspended in the solution, stiffening the liquid into a gel. This reduces the hydrogen production during charging, and any spill is more easily handled because the high viscosity of the medium inhibits its ability to spread.
Other types of batteries are seldom used because of the additional costs involved. However, battery technology is evolving very quickly; new materials and methods for storing energy are entering the market virtually nonstop. Of particular note is the evolution of lithium ion batteries, which are lighter and carry more capacity per pound than most other units (they have about six times the capacity of a similar-sized lead acid battery). From a safety perspective, all lithium batteries require an internal protection circuit to keep the voltage, current, and temperature within safe limits. Should the circuit fail or physical damage be inflicted on the battery, it could ignite with significant heat output.
The size of the installation is an important factor in determining the risk associated with battery systems. A stand-alone UPS battery pack supplying a desktop computer shouldn’t create a significant problem. However, a storage system that supplies an entire computer network in a building or on a floor poses a greater risk. Consider a bank of batteries capable of supplying a large data center; the amount of hazardous material is significant. The off-gassing of certain types of batteries must be addressed using redundant ventilation techniques, and responding firefighters should be well aware of the large electrical installation and its potential for shock hazards.
Fire department concerns with battery storage systems include the following:
• Shock hazards. Most battery systems in buildings contain enough energy to electrocute a person. Treat them as any other energized circuits, and use extinguishing methods appropriate for electrical fires.
• Hazardous materials exposure. Traditional batteries contain highly corrosive acid. Contact with this material will be highly injurious to the emergency responder, and inhaling acid fumes could result in long-term medical conditions or even death. Always wear self-contained breathing apparatus and appropriate protective gear in these environments.
• Combustible metal. Some of this new technology uses exotic metals and other materials to achieve certain goals. Using water on some of these materials will generate a violent reaction. Responders should know the appropriate extinguishing medium to use when they encounter these installations and, if it is known, what the reaction will be.
High-volume low-speed (HVLS) fans. HVLS fans can range from six to 24 feet in diameter. The HVLS ceiling and vertical fans are developed to provide significant energy savings and improve occupant comfort year-round in large commercial, industrial, agricultural, and institutional buildings. A massive 24-foot-diameter fan can move as much as 350,000 cubic feet and can be powered with a two-horsepower motor at a mere 440 watts.
Fire department concerns with HVLS fans include the following:
• Fans can obstruct sprinkler spray, resulting in less water reaching a fire and a change in droplet size and geometry.
• Fans cause accelerated fire spread by providing additional air flow, oxygen, and velocity, resulting in unique fire spread characteristics.
REFERENCES
1. www.firemarshals.org/programs/green-buildings-fire-safety-project/?&static-authorize-sign-is-invalid.
2. www.osfm.fire.ca.gov/training/pdf/photovoltaics/pvstudentmanual.pdf.
3. Paiss, M, “Solar Electric Systems and Firefighter Safety,” Fire Engineering, May 2009.
JACK J. MURPHY, MA, is a fire marshal (ret.) and former deputy chief for the Leonia (NJ) Fire Department. He is also a licensed New Jersey state fire official. He serves as a board trustee for the New York City High-Rise Fire Safety Directors Association, a member of the National Fire Protection Association’s High-Rise Building Safety Advisory and Pre-Incident Planning Committees, and a deputy fire coordinator for the New Jersey Division of Fire Safety (Bergen Region). He has published various fire service articles, authoring the RICS-Rapid Incident Command System field handbooks and the Pre-Incident Planning chapter of Fire Engineering’s Handbook for Firefighter I and II. He co-hosts the fireengineering.com “Taming Your Work Environment” podcast and is an advisory board member of Fire Engineering and FDIC. Murphy has a master’s degree and several undergraduate degrees.
JIM TIDWELLwas a 30-year member of the Fort Worth (TX) Fire Department, serving as a fire marshal, an executive deputy chief, and chief of department (interim). After leaving the department, he led the International Code Council’s (ICC’s) Fire Service Activities Team, where he spearheaded efforts to provide opportunities for fire service input and influence in the ICC code development system. Tidwell has actively promoted fire service issues on a local, state, and national level for many years, which includes service on ICC and National Fire Protection Association code development committees, working with legislative and executive branches of government to ensure fire service issues are recognized, and volunteering for the National Fallen Firefighters Foundation on a number of projects.
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