Green, or sustainable, building continues to increase in popularity and frequency, spurred by environmental concerns, financial incentives, and increased regulations. “Going green” means minimizing the effects of the built environment through the efficient use of resources, reduction of waste and environmental discharges, and a focus on human wellness and health. While green technologies can have obvious benefits in the short and long term, many of the evolving design elements and techniques can create new or changed risks, especially in the event of a fire. It’s imperative that professionals in fire service and insurance understand those risks so they can manage and mitigate them to the maximum extent.
To evaluate fire-related risks associated with the green movement, we should first consider what green building is. The U.S. Environmental Protection Agency defines green building as “the practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle from siting to design, construction, operation, maintenance, renovation, and deconstruction. This practice expands and complements the classical building design concerns of economy, utility, durability, and comfort. Green building is also known as a sustainable or high performance building.”1 There are a number of rating schemes for green buildings, such as the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) system. In general, these rating schemes do not directly address a building’s fire protection design and features.
Numerous aspects of green technology, such as energy-saving ventilation designs, and site-related issues, such as the load-bearing capabilities with respect to fire apparatus of nontraditional roads and landscaping, can limit or complicate apparatus access to a building during a fire. This article, however, focuses primarily on construction-related effects within the building during a fire.
The goals of green design and construction that stress efficiency in the use of resources, both in terms of materials used and energy consumed, have led to many changes in construction methods, techniques, and materials. One example is the prevalence of large open spaces that maximize natural lighting, remove barriers that improve heating and cooling efficiency, and increase the feeling of openness for occupants.2
Another major consideration is the change in fire load, specifically changes occurring over the last 30 to 40 years that have seen the evolution from cellulose-based furniture and other contents to synthetic or petroleum-based materials. The result is impressively apparent in UL’s (Underwriters Laboratories) video comparing modern and legacy living room furnishings.
The comparison of time to flashover of 3 minutes 30 seconds for the modern room versus 29 minutes 30 seconds for the legacy room is staggering. The inclusion of green structural and insulation materials of recycled wood and plastic further add to the potential increase in fire load.
The following is a detailed discussion for some of the key green building materials and methods.
Lightweight construction materials
While lightweight construction is not unique to green buildings and has been prevalent since the 1980s, the industry encourages lightweight wood trusses and engineered lumber in modern construction as a green alternative to full-dimensional lumber. The use of lightweight construction materials reduces the consumption of raw materials and allows the use of recycled wood products. Examples include trusses with gusset plates, glue-laminated beams, and structural composite lumber. While beneficial from a sustainability perspective, those new construction techniques also change the level of risk.
“Ongoing changes in construction methods, building materials, home designs, and products used in home furnishings present new potential safety challenges under fire conditions,” says Steve Kerber, director, UL Firefighter Safety Research Institute. “UL has been conducting research with fire departments across the country into the characteristics of the modern residential fire to reduce safety risks and to protect the lives of firefighters and occupants alike.”
A recent research project jointly conducted by UL and the Chicago Fire Department4 indicated that lightweight construction burns and collapses faster than conventional solid wood members. It’s one of several studies5 conducted by UL under the direction of Kerber in collaboration with other organizations, including the National Institute of Standards and Technology (NIST), the Fire Department of New York (FDNY), and several academic institutions.
Truss construction also allows for larger spans, which results in more open space and less compartmentation. The use of these trusses in floor systems also creates void spaces that can delay fire detection and facilitate horizontal fire spread.
Lightweight construction also changes firefighting tactics. Recent UL studies identified ventilation as a primary consideration in the outcome of fire suppression operations. Since lightweight construction members are likely to fail more quickly and typically without warning when compared with traditional sawn lumber, firefighters must exercise extreme caution in personnel placement above and below the fire. Recognition of the presence of lightweight construction and the determination of involvement of those structural elements in a fire event are a top priority for responders. Incident commanders should strongly consider defensive operations when lightweight structural elements are exposed to fire conditions. Insurers should recognize that defensive operations typically lead to larger or complete property loss. We can mitigate that risk to a certain extent by early detection and the installation of fire sprinklers.
Firefighter awareness and recognition of the presence of lightweight construction are essential. That can be best accomplished through training, effective preplanning, and good communication with building departments. Some state and local jurisdictions have regulations that require warning signs or placards that indicate truss or other lightweight structural components in the floor or roof. This link shows some examples.
Insulating materials
To facilitate energy conservation, the addition of insulation is a common aspect of green building. But if improperly constructed, some insulation materials can result in faster fire spread and the generation of toxic products of combustion.
Insulation can be installed in the interior or on the exterior of a building. Insulating materials can consist of fiber-reinforced polymer (FRP), rigid foam, spray-applied foam, structural integrated panels (SIP), and exterior insulation and finish systems (EIFS). All of those insulations are primarily polyurethane or expanded or extruded polystyrene; SIP panels consist of rigid foam sandwiched between two layers of wood or metal to achieve desired strength and insulation values.
Green insulating materials have many advantages. They’re lightweight, made of recycled plastic, and have a high R-value (a measure of thermal resistance). It’s important to use the appropriate approved materials with proper protection. Nonapproved insulating materials that aren’t treated or are exposed without an appropriate barrier can burn intensely and generate large quantities of toxic products of combustion. Without adequate protection to the insulation or where nonapproved plastic insulation panels are used, the building can present a significant fire hazard.
The fire that occurred on February 9, 2009, at China Central Television (CCTV) headquarters in Beijing is an example of a fire that spread quickly through the entire building fueled by nonapproved extruded polystyrene insulation panels behind alloy curtain walls. Strong code adoption and enforcement practices help ensure the use of appropriate materials and the proper installation and arrangement of insulation systems.
Another consideration is that well-insulated structures, especially with high-performance glazing, contain the heat from a fire. In those cases, firefighters can anticipate accelerated time to flashover.
Photovoltaic (PV) solar panels
An often-used green initiative is photovoltaic (PV) solar panels to generate electrical power. A PV system typically includes the PV module (array) that generates electric direct current from the sun’s energy, inverters that convert direct current to alternating current, and disconnects that isolate the PV module (array) from the building’s electrical circuitry conduit. The system may include an electric storage device (batteries) to store the solar-generated electricity. Even if you can disconnect the PV system, a PV module will always generate electricity when the sun shines. Therefore, the units will almost always contain energy and can present a significant electric shock hazard to firefighters should a fire occur.
In addition to the shock hazard, a PV system poses other safety considerations. Structural collapse is a concern due to the added weight from the system, especially when structural elements experience fire conditions. The PV panels and system components can be combustible and add fuel to a fire, and the PV system can also provide an ignition source.
Solar power installations can obstruct access for firefighting activities, including vertical ventilation and stretching of hose lines, thereby reducing the effectiveness of suppression operations. Strong building code adoption and enforcement can address structural load requirements and proper installation of the PV system. Fire department standard operating procedures (SOPs) or standard operating guidelines (SOGs) should be in place to clarify response strategies and tactics. Identifying and preplanning such installations are also essential components of effective response.
Vegetative roof
Another popular green initiative is a vegetative, or green, roof on a building to reduce the carbon footprint and improve insulation. Green roofs typically consist of a growth medium on top of a root barrier, drainage and water-retention layers, and a waterproof base. Foliage is planted in the growth medium. A green roof reduces building energy consumption, and the overall positive effect to the environment is unquestioned.
A properly designed and well-maintained green roof can actually reduce the threat of a roof fire, since a green roof system contains a large amount of aggregate material that is not combustible. However, a green roof can pose potential risks to the building itself or neighboring buildings if it’s not designed and maintained properly. A vegetative roof can accumulate dead or dry plantings that provide a highly combustible fuel source that could cause a fire to spread within the building or to adjacent buildings.
Other risks include roof collapse if the underlying structure experiences the effects of fire, possibly enhanced by the saturation of the growth medium from fire streams or a malfunctioning drainage system. Additionally, green roofs may affect fire department access and hinder standard firefighting operations, including ventilation and deployment of fire hoses.
Conclusion
Green building embodies the worthy goal of minimizing the effect of the built environment on the planet and its occupants. With that concept comes new and different risks that, if not managed, can result in increased chance of structural collapse, faster time to flashover, and fire events that generate more toxic products of combustion. The good news is fire detection and suppression systems can provide a high level of risk mitigation.
In many ways, the fire service has begun to adapt to the risks, but there is more work to do. Preplanning is essential so that firefighters are aware of where and what green building concepts and technologies are employed. Changes in strategies and tactics could be necessary. They include proper ventilation in coordination with hose teams and transitional attack using exterior streams to reduce fire intensity.
Specialized training is also a key consideration, as it can help firefighters and insurers recognize and comprehend the changing risks associated with green buildings, identify building construction, and understand fire dynamics. A solid incident command system (ICS), good fireground communication, and the use of standard operating procedures and guidelines are also essential.
Strong building codes and enforcement are another critical element of managing and mitigating risks of green building. That will help ensure adequate access and appropriate construction materials and techniques, including the use of approved materials and fire barriers and the suitability of fire detection and suppression systems. A strong fire inspection program helps ensure that installations and systems are maintained within prescribed parameters.
As always, the highest priority is the safety of the public and responding firefighters, followed by the protection of property and the environment. While green building creates challenges, the tools mentioned above improve our chances of a successful outcome.
1See US EPA link http://www.epa.gov/greenbuilding/pubs/about.htm
2Bridging the Gap – Fire Safety and Green Buildings Guidehttp://www.firemarshals.org/greenbuilding/bridgingthegap.html