Web Exclusive Feature! Fire Protection for Glazed Windows
Currently, there is also confusion between the term, "Listed Window Sprinklers," as advertised by some manufacturers. If you were to look in the Underwriters Laboratories (UL) Fire Protection Equipment Listing Directory, you will find a listing category titled: "Sprinklers, Outside (VOKR)." Under this heading, you will find an explanation stating, in part: "These sprinklers are non-automatic and are intended for protection of windows, walls and roofs against exposure fires." These nozzles (none in this category have operating elements) are intended for use with deluge systems to provide exposure protection and will not provide a fire resistive rating.
For quite some time, standard spray sprinklers with fusible elements have been used to protect glazing in walls that were required to be fire rated. These walls may have been required to maintain an occupancy separation by the building code. They may also have been required to carry a two-hour fire rating because they were part of an egress corridor. This is typically required to assure safe passage of occupants out of a building during a fire.
During the design phase of a building, the design team--possibly consisting of the architect, engineer, insurance underwriter, (hopefully) the local fire authority and others--would meet to discuss the requirements for the particular project. The aesthetic desire for the use of glazing to create an open, airy feel in the building would often result in conflict with required building and fire codes. This conflict would usually be resolved by concessions from the building and fire authorities. It seemed reasonable that if closely spaced sprinklers were located near the glass, this would create a kind of "water curtain," thereby protecting the glass from failure.
More questions remain. Will the sprinkler(s) respond quickly enough to prevent thermal shock once the water discharges onto the hot glazed surfaces? What data and testing was used to allow the use of these sprinklers in this particular application? Did the building code or fire code reference specific criteria and requirements for this installation? Who assumes liability, the installing contractor or approving authority?
A New Way of ThinkingTo answer these questions, sprinkler manufacturers had to consider a new design for automatic sprinklers specifically for use with glazed windows. The new window sprinkler that resulted from these deliberations was designed to offer both exposure protection and fire resistance to meet multiple code requirements.
And because these sprinklers and their use, in conjunction with glazed partitions, went a step beyond the typical use of automatic fire sprinklers, it was also necessary to step beyond the traditional listing procedures and reports. Evaluations and corresponding reports were sought from the National Evaluation Service (NES), the ICBO Evaluation Service and the Building Materials Evaluation Commission (BMEC) of Canada. And a "Specific Application Sprinkler" listing was established at Underwriters Laboratory under the category "Window Sprinklers" to test the sprinklers and ensure that they do provide a fire resistive rating.
In 1995, the test program was established in conjunction with UL for the purposes of determining if the window sprinklers, when located within specific parameters, and with a specific discharge pattern, would maintain the integrity of single pane, heat-strengthened glass for two hours, when subjected to a window exposure fire test, as well as a 40 kW fire test at the base of the glazing.
The window exposure fire test utilized test furnaces which were calibrated to bring room temperature up to 1,832 degrees F (1,000 degrees C) over a period of two hours. This was done to maintain the standard time-temperature curve specified in ASTM E-119 (Figure 3) and CAN/ULC-S101-M89.
These tests included glazing assemblies connected with vertical mullions as well as glazing assemblies that were connected by a silicone butt joint.
After successful completion of the tests and the establishment of subsequent installation parameters, these new types of window sprinklers were approved for use as an "equivalent method of construction," when acceptable to the Authority Having Jurisdiction, to provide an equivalency of a two-hour rated partition when using glazed assemblies. Thus, by stepping beyond the traditional use of automatic sprinklers, a new design was able to unite the concepts of exposure protection and fire resistance in these glazed window applications.