Green design, HVLS fans, and the challenges for sprinkler designers + installers
NFPA Journal®, March/April 2013
The world would be a lot easier for sprinkler system designers if sprinklers were the only system in the building. The reality is that between mechanical systems, plumbing systems, structural systems, and all the other components necessary to make a building function, the sprinkler designer has many challenges to effectively locate sprinklers in a building.
The concept of designing around “obstructions” and other building components has been around for more than 100 years. Over that time, NFPA 13, Installation of Sprinkler Systems, has evolved to address the placement of many types of sprinklers around many classifications of obstructions. While it is not practical for the spacing and obstruction rules in NFPA 13 to cover every building configuration, most common arrangements can be linked to one or more of the spacing and obstruction rules. Every so often, however, a new challenge comes along that requires specific rules for locating sprinklers.
The push for green building design and energy conservation has resulted in new mechanical systems and design approaches to meet these “green goals,” and these new systems and approaches can create challenges for sprinkler designers and installers, who are commonly the “last men in” on a project. The latest such challenge is the high-volume low-speed (HVLS) fan. These behemoths are becoming more and more prevalent in warehouses and large open spaces. HVLS fans use long blades rotating at low speeds to provide effective ventilation and maintain the desired temperature and humidity. The low speed of these fans allows for efficient energy use, while limiting the turbulence and noise created by the rotating blades, which can have a diameter of up to 24 feet (8 meters). When faced with a fan that big, the sprinkler designer’s first question is, “How does this affect my sprinklers?”
NFPA’s Technical Committee for Sprinkler System Discharge Criteria first discused this concept before the publication of the 2010 edition of NFPA 13. At that time, the committee did not have any data on the impact of these fans, and the standard included no design requirements.
The following year, the Fire Protection Research Foundation (FPRF), working with leaders from the insurance industry, stepped up to help find some answers. The FPRF, an invaluable resource to the NFPA technical committees, set up a project to study the effects of these fans on sprinkler performance in full-scale testing scenarios. These tests studied the impact of the fans on sprinkler systems, focusing on activation time and spray pattern development.
The findings of the study, available at nfpa.org/foundation, were presented to the discharge committee, which used the information to develop a new set of design rules pertaining to this equipment for the 2013 edition of NFPA 13.
These new rules require the fan to be limited to 24 feet (8 meters) in diameter, with the sprinklers arranged such that the fan is centered on four adjacent sprinklers. The fan installation must be coordinated with the sprinkler design in such a way that the distance between the fan blade and the sprinkler deflector is at least 3 feet (0.9 meters), to limit the impact of the airflow on the sprinklers’ activation time.
This new technology, which started as a design challenge for the sprinkler industry, became a true success story. The collaborative efforts of the FPRF, the insurance industry, the NFPA sprinkler committees, and the HVLS industry, which was an actively engaged supporter of the project, proved that “new” does not have to mean “scary.”
Matt Klaus is a senior fire protection engineer at NFPA and staff liaison on NFPA 13, 13R, 13D.