Styling with fire-rated glass

by sadia_badhon | April 3, 2020 12:48 pm

By Connor Martin

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As encouraged by Frank Lloyd Wright in his famous quote, “Form and function should be one, joined in a spiritual union,” architects and designers can merge the use of glass with the function of fire-rated partitions to achieve esthetic outcomes while complying with building codes.

In few arenas has the move toward this unity been more apparent than that of fire-rated glazing systems. For decades, the only glass option offering a degree of fire protection was polished wired glass. Polished wired glass was a hindrance to achieving the design intent because of limited allowable areas, questionable safety characteristics, and the wires themselves, as they created an imperfect transparent separation. Glass openings in fire doors were greatly limited in size based on fire rating and location. Further, if the installed glass ever broke, the wires would create sharp snags that could cause potential entrapment and injury to people using the exit.

Despite these drawbacks, wired glass was the only one on the market that could remain in the frame during fire tests. As a result, it became a ubiquitous presence wherever fire safety was a concern.

The lack of diversity in available materials meant  that the vision for a building’s look and feel had to accommodate the one product that could protect building occupants.

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The good news is that the last few decades have witnessed an explosion of innovation in fire-rated glass, glazing, and framing materials. Today’s product range offers options that surpass traditional wired glass in fire performance and provides a variety of appearances that contributes to and enhances the overall design of fire-rated separation.

The benefits of redundancy

Fire-rated glazing plays an integral role in a building’s overall fire and life-safety protection plan through the vehicle of compartmentation. By safeguarding against the spread of flames, smoke, and, in some instances, heat, the material helps contain a fire. The sub-division of space helps buy time for occupants to exit the building and firefighters to arrive and extinguish the fire. While this passive form of protection may seem unnecessary in a world of smoke detection and suppression systems, the redundancy is paramount in creating a holistic and well-balanced, fire- and life-safety plan.

Smoke alarms, heat sensors, and sprinklers are vital weapons in the fight against fire. They alert occupants to the threat of fire and provide initial and crucial suppression against flames and smoke. As ‘active’ systems, they rely on an action or trigger to perform properly.

Passive materials like fire-rated glazing do not require activation. They supplement active systems, helping limit the rate of fire growth. In effect, they allow more time for active systems to alert occupants of a fire threat and/or suppress flames and smoke for safe occupant evacuation.

Since active and passive systems work in tandem, they also reinforce one another. For example, while active systems often perform as expected, it is possible for a fire to exceed the size for which the systems have been designed. Further, sometimes a given system may fail to activate. In either scenario, if the detection or suppression system has been rendered ineffective, the passive system is still at work defending against the spread of fire.

Clear needs, clear choices

Today’s glass products have diversified not only the way they enhance fire safety through passive protection, but also in how they are classified as building materials. There are now two primary categories of fire-rated glass: fire protective and fire resistive.

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Fire-protective glass aids in compartmentalization, preventing the spread of flames and smoke from one section of a building to another. It is approved for use in windows, doors, transoms, and sidelites. To achieve this status, fire-protective glass must prove it can remain in frame during intense heat without shattering or slumping out of the opening. It must also demonstrate that, once heated, it can resist the thermal shock of cold water from sprinklers or a fire hose. Failure at either stage could create a breach where the flames, smoke, and toxic gases could travel further throughout the building, jeopardizing life and property.

New fire-protective glass options can satisfy the requirements of the Underwriters Laboratories of Canada (CAN/ULC) S106-15, Standard Method for Fire Tests of Window and Glass Block Assemblies. They are also able to meet CAN/ULC S104-15, Standard Method for Fire Tests of Door Assemblies.

Fire-resistive glass goes a step further, and blocks radiant and conductive heat transfer. This means that it functions the same way, and meets CAN/ULC S101-14, Standard Methods of Fire Endurance Tests of Building Construction and Materials, as a solid barrier wall. It can be specified in floor-to-ceiling sizes as well as in wall-to-wall and horizontal assemblies, thereby expanding design freedom.

To achieve such a high level of fire performance, fire-resistive glass is typically thicker than its fire-protective counterpart. One prominent product is composed of multiple layers of glass sandwiching clear, intumescent interlayers. When heated, the interlayers turn to foam, thereby obscuring vision but preventing heat from passing through the wall. Even if a flame is burning on one side of the glass, the opposite surface would remain cool enough to touch.

This becomes important in areas such as stairwells that require a temperature-rise rating to protect building occupants for the time period they are transiting through the exit. Since structural fires can quickly exceed 871 C (1600 F), maintaining a safe temperature is as important as fire containment.

A better framework

When a glass system undergoes testing to receive its fire rating, it must be evaluated using appropriate glazing materials within a compatible framing system, and all components must meet the same standards. For many years, framing has remained relatively unchanged. The only real choice on the table was bulky, wrap-around hollow metal steel. It did the job, but often did not complement the appearance of the surrounding non-rated framing systems.

Fortunately, the innovation in frames has kept pace with the changes in glass. Architects now have the option of specifying sleek steel frames that are cold-rolled instead of bent. They offer tremendous strength and narrower sightlines and make it possible to have fire-rated curtain walls.

Modern fire-rated frames can be finished to match virtually any colour scheme. They can also be clad in stainless steel or hardwood where desired. The most important consideration is to ensure the glass and framing have been tested as a system and carry identical ratings from an independent laboratory such as Underwriters Laboratories (UL) and ULC.

Having a variety of both fire-protective and fire-resistive options means safety and design can stay a top priority. There is no longer a need to compromise one for the other. In fact, the current levels of performance and esthetic options in fire-rated glass are greater than at any other time in history.

A new and improved ceramics class

One type of glazing material that has changed fire protection is not technically glass, but ceramic. Long known for its ability to tolerate heat, ceramic has been used in everything from cooktops to car engines. Manufacturers created a transparent ceramic that is able to meet fire codes without the use of wires.

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Ceramic glazing’s fire ratings exceed the 45-minute limit traditional wired glass can provide. Further, ceramic is approved for use in larger sizes than wired glass. It is also available with a film or in laminated form to provide impact safety as well. Ceramic can be etched, sandblasted, or installed in insulated glazing units (IGUs) for even more design possibilities. Various surface grades and levels of optical clarity can be specified to suit the application.

Brooklin High School in Whitby, Ont., serves as an example of the difference modern fire-rated ceramic glazing can make. Architects of the 16,090-m² (173,200-sf) high school wanted to include extensive glazing throughout the facility to provide natural light and visibility for students and staff. However, installing wired glass in the fire-rated areas would have altered the ambience, detracting from views and interrupting the seamless appearance of the building as a whole.

As an alternative, designers specified 325 m² (3500 sf) of high-performance, fire-rated glass ceramic in doors, sidelites, transoms, and interior windows throughout the entire school. Clear and wireless, the appearance is virtually indistinguishable from the non-rated glass installed in the building.

The project incorporates two types of fire-rated glass ceramic that provide essential fire protection while also helping to create a welcoming school environment. The multifunctional glass ceramic is also impact safety rated. It meets the American National Standards Institute (ANSI) Z97.1-15, For Safety Glazing Materials Used In Buildings – Safety Performance Specifications And Methods Of Test, and Consumer Product Safety Commission (CPSC) 16 Code of Federal Regulations (CFR) 1201, Safety Standard for Architectural Glazing Materials (Categories I and II), to help prevent injuries from glass breakage if students run into it—important in a busy school serving more than 1100 teenagers.

Glass walls, open possibilities

Fire-resistive glass walls are also changing the landscape of design. In St. John’s, N.L., KMK Place is a four-storey, 7432-m² (80,000-sf) office building designed to stand out. The open floor plan was created in order to provide maximum daylighting and a smooth flow through the building.

Architects created a glazed atrium that provides a focal point both inside and outside the building. It also allows light to reach deep into interior spaces on multiple floors.

The challenge for the design was meeting the National Building Code of Canada (NBC) and local regulations that required the glass in the atrium to carry a two-hour fire rating. This meant it needed to be a fire-resistive glazing system that could function as a wall and serve as a barrier to heat. The design team chose a combination of transparent wall panels and aluminum-clad, fire-rated framing that gave them both the form and function they were hoping to achieve.

“It is not too often that you will see an atrium of this calibre in office buildings,” commented project architect, Sandy Gibbons. “We needed a specialty product that met certain needs like replacing solid walls and creating an open space, while not forcing us to compromise on esthetics.”

Complementary systems in action

The solution-creating abilities of all these new fire-rated options begins to become clear as designers find ways to utilize multiple options at once to give them the result they have in mind.

This is what the Brayton Hughes Design Studios discovered when they planned the renovation of the La Crema Estate at Saralee’s Vineyard in Windsor, Calif. At the heart of the winery is a historic barn dating back to 1900 that now houses multiple tasting rooms.

To bring the barn up to current building code requirements, the designers needed to construct a fire barrier around the tasting room’s historic staircase. It had to be capable of defending against the spread of flames, smoke, and heat transfer without creating an unsightly intrusion. It was essential this new safety feature could maintain the rich allure of wood, complementing the extensive wood framing and hardwood flooring used throughout the surrounding space.

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Rather than resorting to a solid gypsum board enclosure around the stairs, architects opted for fire-resistive transparent glass panels. This enabled them to incorporate an unrestricted amount of glazing that would allow the staircase to remain visible. They paired this glazing with a fire-rated system overlaying a high-strength, steel sub-frame with a domestic white oak-veneered metal cover cap. The result is a stairwell that enables clean sightlines, capturing the warmth of wood and acting as a barrier to fire, smoke, and heat.

In previous decades, the choice in doors for such a stairwell would have been restricted to a solid metal fire door with a small vision kit. However, the architects were able to take full advantage of the latest material offerings and specify a fire-rated glass door in framing that maintains the same visual esthetic as the surrounding fire-rated system.

Further, the design team incorporated another breakthrough: they lined the perimeter of the main staircase with fire-rated glass flooring segments. The advanced fire-rated glass floor system consists of heat barrier glass, a tempered, laminated walking surface, and a steel framing grid. This configuration allows the system to draw light from the upper level down to the ground floor while providing critical fire resistance. It can support loads of up to 732kg/m² (150 psf) and is fire-rated for up to 120 minutes.

The next frontier

In recent years, the trend has been toward glossy spans of uninterrupted glass in prominent applications, such as storefronts, partitions, and visible curtain walls. Until recently, it was impossible to achieve this clean, modern look in areas subject to fire-rated criteria. Now, two systems offer this functionality.

The first is a structural, silicone-glazed, fire-rated curtain wall system. It emulates the smooth, monolithic appearance of its non-rated counterpart and does not require pressure plates or caps. Its toggle retention system anchors the glazed lites and becomes completely hidden once installed. The resultant effect is a seamless, uninterrupted surface appearance. The system is available with up to 120-minute fire-resistance-ratings and can accommodate full-lite doors for a complete curtain wall entrance solution. In application, it can help ensure smooth visual transitions at junctions between the rated and non-rated systems while providing critical protection against the spread of fire.

The second development to capture the continuous glass esthetic is butt-glazed, fire-rated glass walls. Currently available systems comprise fire-rated glass wall panels with butt-glazed joints in a heat-resistive perimeter frame. To further improve sightlines, some assemblies have vertical butt-glazed joints as narrow as 5 mm (197 mils). Offerings with a solid, multi-laminate glass makeup (i.e. those that have colourless, wireless, low-iron float glass and clear intumescent interlayers) eliminate the need for coloured internal spacers or vertical mullions between adjoining pieces of glass.

Adding an element of customization, some systems are now available with perimeter framing options. For these products, the perimeter of each butt-glazed elevation can be held in place by the designer’s choice of fire-rated framing.

With near imperceptible sightlines, butt-glazed, fire-rated glass walls are suitable for interior applications where it is crucial to match the look of neighbouring non-rated systems or improve views and light transmission.

Conclusion

Once an inhibitor to design freedom, fire-rated glass and framing now serve as inspiration, turning possibilities into realities that were inconceivable in the past. There is no longer a need to sacrifice form for the sake of function—buildings can be both safe and beautiful. The creative opportunities continue to expand and the ongoing product development happening in the field of fire-rated glazing only promises even greater potential for the future.

If the proposition of modern, high-performance fire-rated glass appears to be cost prohibitive, one can consider the benefits of bringing esthetics in line with function. Opening up a wall or adding fire-rated curtain walls throughout interiors can enhance daylighting and occupant well-being. Characteristics such as larger glass sizes, increased clarity, higher impact ratings and compliance with energy codes can also improve the user experience and add to the longevity of the building.

[6]Connor Martin represents Technical Glass Products (TGP) in Canada, supporting design and construction activities. TGP is a supplier of fire-rated and specialty glass and framing solutions for the architectural and commercial building industry.

Source URL: https://www.constructioncanada.net/styling-with-fire-rated-glass/

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