Fire Rated Glass Protects Students from the Inside and Out
This article first appeared in the March 2016 issue of Doors and Hardware Magazine.
Architects have always incorporated glazing in their designs for a number of aesthetic and functional reasons – vision, transparency, safety and daylighting to name a few. This is especially important to schools and universities, with several studies confirming that when school spaces are brighter, students learn faster, teacher morale improves, and districts can dramatically cut energy costs. As a result, school districts and their architects are working hard to find new ways to maximize the amount of light reaching into windowless spaces previously designed to control temperatures and prevent student distraction. To capture, pass on and share both daylight and new, environmentally-friendly artificial lighting, glazing has become the material of choice because it allows light to filter from one space to the next. Glazing also has the added benefit of providing clear vision between spaces offering a sense of openness, connectivity and security.
With the advent of fire rated glass, architects can add fire protection to glazing’s many desirable features and benefits by effectively compartmentalizing smoke, flames and in more advanced products, dangerous radiant heat. It performs this life saving function 24 hours a day, 7 days a week without the need for mechanical triggers the way that sprinklers do. While fire rated glass performs the same function every time, its purpose differs depending on whether it is installed in the interior or exterior of a building.
Interior Applications – Ridgewood High School
About 80% of fire rated glazing applications can be found in the interior. This includes openings, walls and door assemblies in exit corridors, stairwell enclosures and occupancy separations. For interior applications, fire rated glazing functions to provide occupants with a path of safe egress or a haven where they can safely await rescue without feeling the devastating effects of flames, smoke and radiant heat.
The level of fire protection needed for each application are laid out in Chapter 7 of the International Building Code (IBC), particularly in Tables 716.5 and 716.6 in the 2012 and 2015 IBC. These tables are not new code requirements, but a clarification of the existing code requirements of Tables 715.4 and 715.5 in the 2009 IBC.
In the case of Ridgewood High School in Norridge, IL, a recent renovation of the stairwell and its connecting exit corridors was an opportunity to use fire rated glass to meet code requirements, maximize vision and create a feeling of openness in a relatively tight space. In the one-hour exit corridors, the fire rated glass specified exceeded 25% of the wall area, which meant the glazed assembly must now meet ASTM E-119 wall requirements and be rated equal to the wall. To meet the design and code requirements, the architect specified SuperLite II-XL 60 in GPX Architectural Series Framing by SAFTI FIRST.
Sound attenuation was also a concern, given Ridgewood High School’s close proximity to O’Hare airport. In the 2009 LEED-NC for Schools guideline, acoustic design is an area where designers can specify materials that can contribute towards earning IEQc9 (Indoor Environmental Quality) credits. To earn this credit, windows in a building’s shell, classroom partitions and other core learning space partitions must meet an STC rating of at least 35. SuperLite II-XL 60, with an inherently high STC rating of 42, helped towards earning this credit while fulfilling the desire to minimize outside noise from one of Chicago’s busiest airports.
The renovation also included a private office for security personnel, and Ridgewood wanted increased privacy for this location while maintaining the natural daylighting aspects and maximum fire protection featured throughout the school. To meet these requirements, SAFTI FIRST supplied SuperLite II-XL 60 with a Satin Etch in GPX Architectural Series Framing.
Exterior Applications – Kromrey Middle School
When fire rated glazing is used in the building envelope, the IBC works to protect the spread of fire from building to building by defining horizontal separation distances and requiring fire resistance ratings for building exteriors that are in close proximity. The IBC measures the building face to the closest interior lot line or to the centerline of a street, alley or public way. If there is more than one building on the same property and exposure protection is necessary, the IBC refers to an imaginary property line. The fire resistance ratings for exterior walls are based on construction type, occupancy and fire separation distance as defined in Section 6 of the IBC, with durations ranging from no rating to 3 hours.
Table 705.8 in the 2009, 2012 and 2015 IBC lays out the percentage of protected and unprotected openings and size limits allowed in exterior walls. Fire protective glass, such as ceramics, wired glass and specialty tempered glass, is either limited in size or prohibited altogether, depending on the fire separation distance. However, the size and area limitations on fire protective glazing do not apply to fire resistive glazing that is tested to ASTM E-119 as they are considered to be walls instead of openings. In instances where code does not allow openings or restricts its size, designers can use fire resistive glazing that is rated equal to the wall to incorporate and maximize vision, transparency and safety while still meeting code requirements.
Fire rated glazing systems used in the building envelope are also expected contribute to the indoor comfort and safety of the occupants. When used as an infill in exterior curtain wall systems, fire rated glazing must consider air infiltration, water resistance, thermal properties, condensation resistance and structural performance, among others. Sometimes, it must also protect against attack, bullets, blast or hurricanes.
In the case of Kromrey Middle School in Middleton, WI, part of the additions and remodel included a dramatic, light-filled glass entrance almost 30-feet high that combined transparent high performance low-e glass panels and opaque decorative panels in a clear anodized aluminum curtain wall frame. Because of the glazing structure’s proximity to the surrounding building, it was determined that the assembly had to meet ASTM E-119 for 60 minutes in order to comply with fire rated code requirements. Aesthetics was also important, so the fire rated systems had to seamlessly match the non-rated systems on campus.
The challenge on this project was taking the profiles of a deeper, fire resistive aluminum curtain wall system and blending them seamlessly to a traditional aluminum curtain wall. As the specified fire rated curtain wall manufacturer for this project, SAFTI FIRST worked with the design team to provide a fire resistive system that incorporated the approved low-e insulated units as well as the decorative wood veneer panels used in the surrounding non-rated curtain wall. It would take a well trained eye to even tell what was fire rated and what was not, which was the ultimate goal of this portion of the project.
To meet the code and design requirements, SAFTI FIRST provided a clear anodized GPX Curtain Wall system with SuperLite II-XL 60 with PPG Starphire Ultra-Clear insulated with Guardian SNX62-27 clear tempered for the transparent panels. For the opaque panels, SAFTI FIRST provided a custom fire resistive wood veneer panel insulated with a clear anodized panel on the interior side. For the 60 minute pair doors with vision lites exceeding 100 square inches, SAFTI FIRST provided SuperLite II-XL 60 with PPG Starphire Ultra-Clear insulated with Guardian SNX62-27 clear tempered in GPX Builders Series Temperature Rise Door Framing. The entire fire resistive system was manufactured in the USA in SAFTI FIRST’s factory in Merced, California.
Advances in fire rated glazing technology over the years has allowed architects to incorporate these products more and more into their projects. Often times, fire rated glazing systems are required to perform multiple functions and meet aesthetic requirements that are expected of non-rated systems. This is where working with a knowledgeable manufacturer in this specialized field becomes key to meeting the performance and design requirements of the project, whatever they may be.