Seeing Through Today's Fire-Rated Glass
- By Julie Stugeon
- August 1st, 2007
Technology in fire-rated glass techniques has made impressive strides in the last decade. No longer relegated to fire-escape doors, the protective glass is even showing up on architects’ drawing boards for atriums and research labs.
Just don’t look for those examples on America’s college campuses.
Unfortunately for administrators, creative uses for fire-rated glass conflict directly with budgets. The old versions ranged from $25 to $30 per sq. ft.; the newer incarnations can top out at $150 to $175 per sq. ft. At prices like these,often architects have resorted to using hard wall partitions when they might have preferred to have some transparency, said Larry Bacher, higher education principal at Gilbane Building Company in Providence, RI.
Of course, where code requires it — mainly in corridor doors — architects have no choice but to comply. In 2006, the National Fire Protection Association tweaked those codes: NFPA 101 and NFPA 5000 require marking any fire-rated windows or fire-rated glazing materials for the material’s approved use (i.e., a wall, a door, etc.) and its rating in terms of minutes. For construction crews, this means when they glance at the product, they can tell instantly if they have the correct materials. Likewise, a code official can easily walk up and check compliance.
In my experience, it’s probably not going to be used on a voluntary basis because the cost is obviously more expensive, said Gregory E. Harrington, principal fire protection engineer at the Quincy, MA-based NFPA.
Let There Be Light
But what the NFPA can’t accomplish by force, Leadership in Energy and Environmental Design (LEED) standards may influence through prestige. After all, in higher education circles, LEED speaks volumes; more than half of the higher education projects Gilbane has in the pipeline are trying to comply with its criteria, said Bacher. And one of those criteria is to pursue greater transparency in building partitions, within an overall goal to use natural light in the building wherever possible — 90 percent of occupied spaces, to be exact. After all, when you use natural light instead of the electric kind, the energy savings pile up.
Not to mention,it’s demonstrated that our biological cycles are set to the rise and fall of the sun, so we are healthier and respond with more productivity and better attention if our bodies experience the cycle of natural light, Bacher pointed out. Campus lab centers and athletic facilities in particular are on the leading edge of this trend. And while mandates depend on the size and height of the building, the sprinkler system, and how the building is used to determine precisely which windows and partitions need fire-rated glass, the law of averages says if architects are specifying more glass, a greater portion will need to boast this technology.
Thank goodness scientists have kept pace. The traditional fire-rated glass most administrators are familiar with contained wires in the glass and required hollow, metal doors for a very industrial appearance. In recent years, that has morphed to a ceramic product, where the core of the glass, under heat, turns into foam that provides the fire protection. Until a fire hits it, said Bacher, it looks like any other piece of glass. Of course, once it is under fire it is no longer a functional window and you’ll need to replace it — but then, he adds, breaking the previous version meant exposing those sharp wires to the public, so most campuses still would need to look at replacement.
The new technology also means that fire-rated glass can escape the 100 sq. in. the wired version was limited to in doors. Today, how long you need fire protection sets those limits — a three-hour rating, for instance, comes with more strings than one that holds for 20 minutes. Most universities find they need one-hour ratings. We have looked for a 45-minute rating on the glass, and that can be a nice piece that provides a good deal of vision and light, Bacher noted. And there are new framing systems developed to match up with this glass that have more narrow profiles and compliment its fire rating. The whole package starts to look more like architectural doors than industrial.
Users also gave the wired glass a thumbs down in the impact-resistance category. There was always a trade-off as to whether you were more concerned by the damage from not containing the fire or about the damage from someone hitting the glass, he added. In fact, the International Building Codes now say the wired fire-rated glass can’t be use in many high-traffic areas for this very reason. Corridor doors, in particular, need clear glass, as would glass near sports activities.
Heat Resistance and Acoustics
The purpose of fire-rated glass is to contain smoke and fire to a limited zone for life safety, and to preserve property. That doesn’t mean the early panes were necessarily good at restricting the transmittal of heat. So officials concerned someone may unknowingly burn themselves pushing against a door where they can’t see the fire on the other side will welcome the news that heat-resistant glass is also available. Some glasses offer better acoustic properties, too, for a better fit in concert halls and meeting rooms. So although administrators don’t need to be current on their code knowledge, they do need to clearly communicate how a building will be used to help the architect work through these choices.
Finally, there’s even a fire-rated glass in existence that can replace a wall assembly altogether. According to Harrington, it looks like glass but is actually a material that can stand up to the same fire tests gypsum boards are subjected to in their lab exercises. It becomes opaque in the presence of heat from a fire and prevents the transmission of radiant heat. Like I said, it’s an expensive product and personally I have never seen it in real installation, Harrington said. But it’s out there.