David Vermeulen, the Midwest territory manager for Technical Glass Products, spends a lot of time talking with Building Teams about impact glazing and fire-rated glass. “There’s still a little confusion about the products—on the types of glass available, how they’ve changed over the years, and how they can be used,” he says. “People are surprised by what they can do with fire-rated glass.”
Here Vermeulen shares some back-to-basics answers to seven common questions about impact glazing and fire-rated glass.
1. How does fire-rated glass differ from ordinary glass?
Fire-rated glass has been tested to act as a barrier to the spread of flames and smoke, a practice known as compartmentalization. The framing and glass undergo independent testing from such organizations as Underwriters Laboratories, where a fire is ignited and the temperature (which can be as high as 1,000ºF after only five minutes) is measured on the surface of the glass. Ratings are given based on the length of time the glass remains intact. The test concludes by blasting the heated glass with water from a two-man fire hose to determine the system’s ability to withstand impact pressure and its resistance to thermal water shock. Fire-rated glass ratings range from 20 minutes up to three hours, depending on the product and framing system.
2. When using glass in fire-rated locations, is impact safety glass also required?
No. Building codes determine where impact safety glass is required. “Generally speaking, any glass 18 inches off the floor or 36 inches from a door—and any door glass itself—has to be safety glass,” says Vermeulen. However, a transom over a door would not require the use of impact-rated glass, so a fire-rated glass that is not impact rated could be used and is a less expensive option than glazing offering both impact- and fire resistance.
3. What types of impact glazing are available?
There are two types: Category I and Category II.
Category I represents 150 foot-pounds of impact, which simulates a small child (approximately 85 lb) running into the glass. Glass meeting this test is limited to a maximum size of nine sf per lite.
Category II represents 400 foot-pounds, which simulates an adult running into the glass, and is the highest level of required impact-rated glass. With few exceptions, all tempered or laminated glass in use falls into this category, and any opening over nine sf has to meet category II standards.
4. What types of fire-rated glass are available?
Two types: thin and thick.
Thin glass is approximately 1/4- to 5/16- inch thick and fits into standard fire-rated steel frames. Thin glass is now available in larger sizes than previously offered—allowing greater design flexibility and larger openings for increased daylighting transfer—with fire ratings from 20 to 90 minutes. Thin products are classified as “opening protective” and block smoke and flames, but are not heat barriers. Thin products are available with or without impact ratings.
Thick glass products, commonly called glass walls because they allow virtually unlimited expanses of glass and are typically used in areas where glazing exceeds 25% of the wall area, measure ¾ inch or more in thickness and are tested to the same standards as solid barrier walls. Fire ratings for thick glass range from 45 minutes up to two hours, and the products block smoke and flames as well as heat.
5. Does fire-rated glass limit design possibilities?
No. “Design possibilities have reached new heights, and that’s triggering a change in the way projects are being built,” says Vermeulen. Advances in glass technology and framing materials address limitations on window sizes and allow windows to meet the same code requirements as a firewall. Vermeulen says designers are now able to use fire-rated glass instead of traditional wall construction to bring more natural daylight into the interior. “We even have fire-rated glass floors now,” he says. New labeling that makes it easier for code officials to determine whether or not the proper glass is used in the space will be part of the International Building Code for 2012.
6. Are fire-rated products more expensive?
Fire-rated glass is more expensive than traditional glass, and typically accounts for 2% of a building’s total budget, according to Vermeulen.
7. Is fire-rated glass traditionally an interior product?
Yes, but that’s changing somewhat. “Insulating fire-rated glass for exterior use is a new thing,” says Vermeulen. In general, fire-rated glass is used on a building’s exterior in cases where adjacent buildings are very close to the property line, to keep fire from leaping from one building to the next. BD+C
David Vermeulen has nearly a decade of fire-rated glazing experience, and has successfully worked with code officials, architects, and designers from schematic product development through installation.
Related Stories
Museums | Apr 27, 2015
Finalists’ designs for Guggenheim Helsinki competition released
A custom-developed App engages an international public in the selection process.
Wood | Apr 26, 2015
Building wood towers: How high is up for timber structures?
The recent push for larger and taller wood structures may seem like an architectural fad. But Building Teams around the world are starting to use more large-scale structural wood systems.
Museums | Apr 23, 2015
Moshe Safdie unveils pentagonal scheme for National Medal of Honor Museum
The new museum near Charleston, S.C., will archive the history of the nation's highest military honorees.
Green | Apr 23, 2015
3 sustainable projects take top prize in 2015 Global Holcim Awards
Projects from Colombia, Sri Lanka, and the U.S. were chosen by the Holcim Foundation for the impact the projects have on their local communities.
High-rise Construction | Apr 23, 2015
Size matters in NYC, where several projects vie for the city’s tallest building honor
The latest renderings of 217 West 57th Street show a tower that would rise higher than the World Trade Center’s pinnacle, when elevations are included.
Multifamily Housing | Apr 22, 2015
Condo developers covet churches for conversions
Former churches, many of which are sitting on prime urban real estate, are being converted into libraries, restaurants, and with greater frequency condominiums.
High-rise Construction | Apr 22, 2015
Architects propose sustainable ‘vertical city’ in the Sahara
Designers aim to make the 1,476-foot tower sustainable, relying on rainwater collection, solar power, and geothermal energy.
Architects | Apr 22, 2015
Architecture Billings Index accelerates in March
For the second consecutive month, the Architecture Billings Index indicated a modest increase in design activity in March.
Green | Apr 22, 2015
AIA Committee on the Environment recognizes Top 10 Green Projects
Seattle's Bullitt Center and the University Center at The New School are among AIA's top 10 green buildings for 2015.
Museums | Apr 22, 2015
Check out Ralph Johnson's stunning nature-inspired Shanghai museum
The newly opened Shanghai Natural History Museum, designed by Perkins+Will’s Global Design Director Ralph Johnson, mimics the shape of a nautilus shell, and features natural elements throughout.