Modern glazing provides safety, beauty

On Nov. 2, 1947, famed businessman and aviator Howard Hughes taxied his hulking H-4 Hercules flying boat across the Long Beach harbor and surprised onlookers, and the world, moments later when he gunned the engines and rose above the water. Pushing engineering and design to the limits, he flew the “Spruce Goose”—the world’s largest aircraft at the time—for nearly one mile. After its first and only flight, the plane was stored in a specially designed hangar and kept in flyable condition for more than 30 years. In 1992, it was moved to the Evergreen Aviation and Space Museum in McMinnville, Ore., for public display.

While they are radically different technologies, there are some parallels between the large wooden airplane and modern fire-rated glass and framing. Both rely on innovative materials and manufacturing techniques, and they expand human thinking regarding design possibilities. Recently, both came together as fire-rated glazing solved a design challenge in a new IMAX theater building on the Evergreen Aviation and Space Museum campus.

Addressing design needs
As part of its mission to inspire and educate people, and promote and preserve aviation history, the Evergreen Aviation and Space Museum constructed a facility with a 232-seat IMAX theater, conference center and open gallery space for displaying historic aircraft. The new building is a scaled replica of the adjacent massive hangar that houses the Spruce Goose, along with more than 85 vintage and modern aircraft. Both buildings incorporate glazing as a key design feature throughout, with multistory curtain walls on their fronts to provide views into the interior from the nearby highway and adjoining parking areas.
The project’s architect, Scott/Edwards Architecture LLP of Portland, Ore., created an open interior design for the theater building that reflects the spirit and inspiration of flight. An 80-foot tall atrium is enclosed by glass on the north and south sides, and the lobby and two mezzanine levels open onto it, where biplanes and triplanes are suspended from the ceiling. To provide sweeping views of the interior and preserve the expansive feel of the space, the architects designed two open staircases. An enclosed staircase set in the back of the building would provide emergency egress in case of a fire.

During construction, however, the building management team requested a design change for the east side upper floors that eliminated the enclosed emergency stairs at the back of the building. To meet building codes, the architects were required to redesign one of the existing open staircases to provide a fire-safe exit. That late in the project, enclosing one of the very prominent staircases with masonry, gypsum or similar fire-blocking materials would have conflicted with the overall building design and marred a dramatic feature—the three-story-high stairs that opened onto the atrium. To address this challenge, the architects proposed instead to use fire-rated glass and frames to enclose the stairs.

Fire glass to the rescue
To meet the various design and code requirements for the enclosed staircase, the fire-rated glass had to do quadruple duty: be clear and wireless with frames that matched the building’s exterior glazed curtain wall as closely as possible; block the spread of flames and smoke for up to two hours; shield people exiting the building from the high heat of a structural fire; and provide safety impact resistance since the glass would be in a floor-to-ceiling configuration.

Scott/Edwards found the solution with transparent wall units installed in fire-rated curtain walls and doors. Such glass units are tested and classified as walls and can block the radiant and conductive heat of a fire, as well as meet safety glazing requirements for impact. Various types of these glass products are available, ranging from older technology that utilizes insulating glass units filled with gel, to modern methods that incorporate multilaminate glass with intumescent interlayers.

For the three-story curtain wall enclosure needed for the stairs, the architects selected Pilkington Pyrostop fire-rated glass and Fireframes Curtainwall Series fire-rated frames from Technical Glass Products, Kirkland, Wash. The glass looks ordinary and  provides a clear view in and out of the stairs. The curtain wall frames and doors are sleek and slender, unlike the bulky wrap-around style of traditional hollow metal steel. Together, the glass and frames are fire-rated for two hours and meet the highest impact safety ratings for glazing: CPSC 16CFR1201 Category II.

The doors leading to the stairs on each level also were required to be fire rated. For this application, the architects used 90-minute Fireframes Heat Barrier Series doors from TGP with Pilkington Pyrostop glass. While heavier than a traditional aluminum door assembly, the ability to provide narrow stile, full-lite fire doors meant the architect could meet all of the performance and aesthetic requirements of the project.

The museum owners were pleased with the fire-rated glazing that looks identical to a second, non-fire-rated glass staircase enclosure, the architects say. “The TGP products integrated well with the overall design,” said Jeff Hammond, project manager with Scott/Edwards Architecture. “The custom colors and frames matched the aesthetics of the other glazing used throughout the project, including the large curtain walls on the front and back of the building.”

Wide-ranging design options

Beyond multistory enclosures for stairwells, fire-rated curtain wall can be used in many other interior and exterior applications. Lobbies and atriums are well suited to the use of curtain wall to provide uninterrupted views; fire-rated curtain walls are increasingly used to safely divide these large interior spaces, while retaining visibility and access to daylight.

For exterior applications, most building codes do not typically require fire-rated materials for the envelope of the building, unless it is close to a property line. However, the outside of the building can play a key role in helping prevent the spread of fire within the building. In some cases, fires have spread from floor to floor along the outside of buildings. Fire-rated curtain wall can help contain fire and stop it from spreading within a building or to adjacent buildings.

The aesthetic advances of fire-rated curtain wall and other types of fire-rated glazing mean that such materials can now be used throughout a building’s design.

Manufacturing and Installation
Glaziers can readily recognize the difference between modern and traditional fire-rated frames, whether for curtain walls, storefronts or other applications. For example, a standard fire-rated hollow metal window wraps around the adjoining wall construction and has a profile of about 3 inches by 6 inches. By comparison, modern fire-rated framing is only a few inches wide, and has hidden fasteners and factory-applied finishes.

The difference in profile size is a result of advanced manufacturing techniques. Typical hollow metal steel framing is formed by bending sheets of steel, which results in a bulky profile. Modern fire-rated framing, on the other hand, is formed from steel tubes instead of sheets, that are given shape in an extrusion-like process. This allows for a wider range of extremely narrow shapes.

Similar to aluminum storefront assemblies, narrow-profile fire-rated framing systems are installed inside the fire-rated opening instead of wrapping around it. This gives a cleaner, sleeker appearance than has previously been available.

Fire-rated curtain wall typically comes knock-down ready to install. The ease of installation helps save on labor time and costs. In one example, a glazier who installed a wall of fire-rated glass lites using the narrow profile frames was able to complete the job in two hours, compared to the 12 hours it usually took with other framing systems.

In many cases, fire-rated glass and frames are provided as complete packages. Glaziers can obtain the needed materials from one source, rather than searching for separate glass and frame suppliers. In addition to convenience and time savings, this ensures that the products are compatible and that the frames have the same fire rating as the glass.

While high-performance fire-rated glass and frames weren't around when Howard Hughes built the Spruce Goose, modern glazing is now playing a role in helping provide a high quality home for visitors to enjoy his and other aviation achievements. Unlike the Spruce Goose, however, fire-rated glass and frames are widely adopted and provide levels of performance for architects and glaziers never before possible.