Window Sprinklers as an Alternative to Fire-Rated Glass

Architects now have a choice in how to achieve fire-rated partition designs
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Sponsored by TYCO
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Demonstrating Window Sprinkler Code Compliance

As noted already, codes and standards require performance levels but don’t dictate the design of buildings or products. Instead they look for evidence that demonstrates performance to match the code requirements for health, safety, and welfare. In addition to the NFPA view on this point, Section 104.11 of the International Building Code reads as follows:

“The provisions of this code are not intended to prevent the installation of any materials or to prohibit any design, or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method, or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability, and safety.”

Using these code provisions as a basis, window sprinklers have undergone a rigorous but well-established process overseen by the ICC, which is summarized in the following paragraphs.

ICC Acceptance Criteria

The International Code Council operates a separate subsidiary known as the ICC Evaluation Service (ICC-ES). According to its website (, it is recognized as “an industry leader in performing technical evaluations for code compliance, providing regulators and construction professionals with clear evidence that products comply with codes and standards.” Its reputation is based on evaluations of hundreds of building products, components, methods, and materials to determine equal compliance with the ICC family of codes.

Acceptance criteria researched and published by the ICC Evaluation Service

Image courtesy of ICC

Acceptance criteria researched and published by the ICC Evaluation Service is used as the generic basis for subsequent reviews of specific products or systems seeking code-compliance approval for alternatives.

The first step in conducting a review or evaluation involves the creation of generic (i.e., non-product-specific) acceptance criteria (AC), which can be looked at as the “performance specification” for a class or type of product. Accordingly, it has created and published acceptance criteria known as AC 385: Special-Purpose Sprinklers Used with Fixed Glazed Assemblies to Provide an Alternative to a Fire-Resistance-Rated Wall Assembly. As with all AC documents, it is clearly stated that “this acceptance criteria has been issued to provide interested parties with guidelines for demonstrating compliance with performance features of the codes referenced in the criteria. The criteria was developed through a transparent process involving public hearings of the ICC-ES Evaluation Committee and/or online postings where public comment was solicited.” Hence a thorough and very open process is engaged before the AC reports are crafted, reviewed, and issued.

Independent Testing

Consistent with all code-based performance, the ICC-ES relies on independent laboratory tests following code recognized testing standards. AC-385 for window sprinklers follows that practice and references the most relevant and well-known standards for fire testing. These include either ASTM E-119: Standard Test Methods for Fire Tests of Building Construction and Materials or the very similar UL 263: Standard for Fire Tests of Building Construction and Materials. Either of these tests exposes a specimen of the material or assembly being tested to a controlled fire in a test chamber with specified temperatures for a specified time period. As such, the test provides “a relative measure of the fire-test response of comparable building elements under these fire exposure conditions.” In the case of walls and partitions, it produces a measurement of the transmission of heat and the transmission of hot gases caused by the fire. The length of time that the wall or partition remains intact enough to resist the transmission of heat and hot gases at the prescribed level ultimately determines it’s fire-resistance rating (e.g., 30, 60, 90, or 120 minutes).

ASTM E-119 diagram with temperature on Y-axis and Tim(minutes) on X-axis

Image courtesy of Johnson Controls

Independent testing following established standards is the recognized method of determining the performance of products and systems for code compliance.

AC-385 recognizes that, under these standards, there is an inherent difference between testing an opaque wall and testing a surface that is being sprayed with water; namely, the water lowers the temperature on the test surface. Therefore, they prescribe a calibration procedure for the test chamber based on setting the test furnace at the same level of natural gas flow rate as for a gypsum wall board assembly that achieves a 3-hour rating. The rationale behind this calibration is that this is the best way to achieve the time-temperature curve that is prescribed in the ASTM E119 or UL 263 standards.

Although not specifically called for in AC-385, the use of ANSI/UL 10B: Standard for Fire Tests of Door Assemblies has also been used as a relevant testing standard. Section 10 of this standard includes a hose stream test to determine how a heated surface in a partition responds to a stream of water. In this case, the surface being tested would be the window to see whether or not it cracked or had other physical damage due to the water spray. Windows with window sprinklers have undergone this test and the glass has remained intact, indicating that windows with window sprinklers are able to meet the same fire-resistance rating as fire barrier assemblies.

ICC-ES Reports

When a manufacturer has a specific product to be reviewed, then it can use the ICC-ES process to demonstrate the performance of that product. So, for window sprinklers, a manufacturer can use the AC-385 criteria and engage an independent test laboratory to conduct the requisite tests and report the results. If those results indicate that the product meets the criteria, then the manufacturer can submit that data for review to the ICC-ES and request a formal report indicating code compliance. Of course, if the test results do not indicate code-compliant performance, then the manufacturer needs to re-design or otherwise modify its product until the test results are favorable.

The difference between the ICC-ES Report (ESR) and the Acceptance Criteria document is that the ESR is issued based on the evaluation of a specific manufactured product. The ESR will follow the requirements of the AC but then apply them to the product and the information submitted for review. Typically, ESRs will identify such things as the evaluation scope (relevant code and reason for evaluation), the intended uses of the product, a general description of the product and any related systems or products inherent in their use (i.e., window sprinklers and windows), and installation details. This information makes it very clear to everyone involved what the evaluation is based on and is limited to provide a very specific, very clear assessment. In addition, the ESR will commonly indicate a few more important points, including conditions of use for achieving code-compliant performance (typically based on conditions outlined in the AC). The ESR will also identify the data submitted for review and the means of identifying the product in the field as distinct from other products.

Authorities Having Jurisdiction

All of the above steps ultimately lead up to the use of a product or system in building construction that the local authority having jurisdiction (AHJ) can review and approve for use. If the design professionals have chosen to incorporate an acceptable design alternative, such as window sprinklers, into the construction documents, then the AHJ has the duty to require documentation of acceptability of the specific products being used. Therefore, the relevant AC and ESR documents need to be listed as required submittals in project specifications so they can be reviewed by both the design professionals and the AHJ. Based on the comprehensive and open nature of developing these documents as described, all involved can reach out to the ICC-ES in the event there are any questions or concerns. More typically, the documents readily demonstrate appropriate code compliance for glazed walls.

One point that is sometimes misunderstood by architects and an AHJ is the use of window sprinklers at doors. Both the Acceptance Criteria AC 385 and the ESR reports contain the following Conditions of Use (paragraph 5.1.7 in AC 385 and 5.8 in ESR-2397): “The assembly is not permitted to incorporate penetrations. Openings must be protected in accordance with IBC requirements for opening protection.” Therefore, if an architect designs and an AHJ approves a glazed wall with doors using these specific types of special purpose window sprinklers, then code compliance can only be shown if the openings are further protected according to the IBC as required above. If not, then the doors are a breach in the fire rating since window sprinklers are not proven to be a code-compliant alternative for unrated doors, even though they may have been accepted locally. That can leave the architect of record liable in the event of a fire so diligence in the proper code-compliant protection of doors in glazed walls is important.


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Originally published in Architectural Record