Tag Archives: Schools

Using Gypsum Wallboard for Acoustic Control

All images courtesy CertainTeed

All images courtesy CertainTeed

by Ashwin L. Himat

With growing acceptance of acoustic control as a key contributor to indoor environmental quality, building project teams are looking for practical, new ways for reducing ambient noise to enhance occupant comfort and concentration.

As the largest continuous surface of a room, ceilings are often the first target of noise reduction strategies, but wall assemblies also play an important role in creating good acoustics. With the right blend of building materials, they can be effective sound-dampeners and barriers against the transmission of noise between rooms.

Unfortunately, many traditional acoustic control design techniques for wall assemblies have gained a reputation over the years for being either too expensive or problematic to install. In many cases, even minor installation errors can compromise the entire wall assembly’s acoustical performance. Thanks to the emergence of new technology and innovation, however, building product manufacturers are introducing more practical options—such as laminated noise-reducing gypsum board— for accomplishing the same objective.

Before looking at wall assembly materials, though, it is helpful to build a good knowledge of the science fundamentals associated with sound, how important acoustic control is to commercial and institutional building markets, and the various building standards guiding acoustical design in these markets.

Acoustical science fundamentals
Most architectural acoustic situations consist of a sound source, transmission path, and receiver. Sound originates from various sources outside the building or adjacent spaces inside. Its transmission paths are building elements through which ambient noise from the source travels.

Measured in decibels (dB), sound intensity ranges from very faint to intolerable sound levels.

Measured in decibels (dB), sound intensity ranges from very faint to intolerable sound levels.

Another potential path of airborne sound transmission is through openings in building walls and ceilings such as open doors, windows, mechanical grilles, and ductwork. Alternatively, the path can be structure-borne, since sound transmits through solid materials even more than it does through the air.

The ‘sound receiver’ is a person or group of people who occupy the building space and hear the sounds passing through. The transmitted sound’s effect on the receiver is the issue that drives the need for acoustic control in building design. For sound receivers, hearing a small amount of pleasant background noise is often an enhancement to indoor environmental quality. However, as the intensity of sound increases, so does the chance it interferes with occupants’ daily activities, such as phone conversations, mental focus, or conducting a class.

Sound intensity, or loudness, is measured in decibels (dB) and can range from very faint to intolerable sound levels. The more intense the sound, the higher the decibel level and the higher the detrimental impact on people, as depicted in Figure 1.

Ambient noise
All background sound in an indoor environment—including from outdoors, building services, utilities, and conversations or functions of people in adjacent spaces—is generally referred to as ambient noise. While a certain amount of ambient noise in the background is common, an excessive amount can seriously degrade the ability to communicate, making it more difficult for people to hear and speak without raising their voices.

In the field of acoustic design, this fact is addressed with the signal-to-noise ratio (SNR)—the measurement of the level of sound from one source in a room, such as a schoolteacher speaking, as compared to the level of ambient noise with which it must compete. SNR specifications are important sound level measurements used in describing the acoustic capabilities of rooms, as well as the quality and performance of many electronic sound components.

Among acousticians, it is generally accepted most people in average public spaces would need to speak at least 15 dB louder than the ambient noise level to be heard at all. Therefore, a conversation that would normally register moderate sound levels—40 to 60 dB—can encroach into the loud sound range—60 to 80 dB—when the speakers try to overcome background noise already in the moderate sound level range. Hence, it is best for ambient noise to be limited to less than 40 dB in a space where conversations or public speaking are regularly taking place.

Sound transmission class
A project’s acceptable ambient noise level goals are achieved by restricting unwanted sound from entering the spaces being designed. This means creating wall, floor, and roof components or assemblies that first effectively block the amount of airborne sound transmitted through them. The measurement for this effectiveness is determined by a sound transmission class (STC) rating.

Sound transmits through wall assemblies, as shown in the above diagram, which also lists the average sound transmission class (STC) ratings for rooms in different building categories.

Sound transmits through wall assemblies, as shown in the above diagram, which also lists the average sound transmission class (STC) ratings for rooms in different building categories.

A higher STC rating means more airborne sound is blocked by the component or assembly. Lower STC ratings mean more sound passes through the components or assemblies, adding to the background noise level in the space—this degrades occupant ability to hear and understand speech.

Contrary to popular notions, airborne sound does not exactly pass through a structural element. Sound generated on one side of a wall energizes the wall structure and sets it in motion, much like a diaphragm. The wall itself becomes the transmitter of the sound energy, which can be heard on the opposite side of the wall by the listener. Hence, the ASTM test methods used to determine STC ratings have focused on this direct-transmission process.

Currently, the STC number is derived from sound attenuation values tested at 16 standard frequencies from 125 to 4000 Hz. These transmission-loss values are then plotted on a sound pressure level graph, and the resulting curve is compared to a standard reference contour. Acoustical engineers fit these values to the appropriate Transmission Loss (TL) curve to determine a final STC rating. Figure 2 demonstrates how sound transmits through wall assemblies, along with average STC ratings for rooms in different building categories.

STC is an accurate measurement for speech sounds, but less so when it comes to amplified music, mechanical equipment, transportation, or any noise with substantial low-frequency energy below 125 Hz. As a supplement to STC ratings, outdoor-indoor transmission class (OITC) is a standard used for indicating the rate of transmission of sound between outdoor and indoor spaces in a structure that considers frequencies down to 80 Hz (e.g. aircraft/rail/truck traffic) and is weighted more to lower frequencies.

Impact insulation class
Beyond airborne sound, it is important for multi-story building designs to address the resistance of structure-borne sound, usually created by people walking or creating other impacts onto the floor-ceiling above a space. Similar to STC ratings, which address airborne sound, floor-ceiling assemblies can be evaluated based on impact insulation class (IIC) ratings.

IIC ratings reveal the ability of a floor-ceiling assembly to absorb or deflect impact/structure-borne noise and keep it from being transmitted to the space below. A floor-ceiling assembly with a low IIC rating permits distracting noise to be transmitted into the room below, leading to the associated problems of distraction and hampered communication.

Reverberation time and speech intelligibility
Reverberations, or echoes, are created when noise reflects off hard surfaces, such as concrete and glass, in interior spaces. Reverberation time (RT) is the acoustical concept measuring how many seconds it takes for a sound to become inaudible in a space. Excessive reverberation can impair speech intelligibility, as the echoes often distort speech and impair verbal communication.

School classrooms require more stringent control of noise to ensure optimal learning or healing for occupants.

School classrooms require more stringent control of noise to ensure optimal learning or healing for occupants.

Measuring RT is important for determining the sound quality of speech and music in rooms. The acoustics of instructional spaces (e.g. classrooms) are at their best when RTs are short—less than 1.0 seconds, specifically. This ensures clarity and high speech intelligibility. Speech generated in a space with a RT of longer than 0.6 seconds is considered difficult to understand. Although some reverberation within a space aides speech distribution, longer RTs will cause a buildup of noise and degrade speech intelligibility. Auditoriums, theaters, and other musical venues, however, will typically benefit from longer RTs—often greater than 1.5 seconds.

RT is determined by looking at both the room volume and sound absorption rate in an acoustical space. The volume of a space is proportional to its RT—the greater the volume, the longer the RT. Inversely, the amount of sound-absorbent material in any space has a negative effect on the RT. For example, a large space with tiled floors and a gypsum board ceiling has a long RT. Conversely, a small room with a low suspended fiberglass ceiling and high-pile carpet has a much shorter RT. The key is to find the right balance of sound-reflective and absorbent surfaces for a particular interior space.

Directly related to RT is the amount of sound energy absorbed upon striking a particular surface. The more sound energy absorbed means less is reflected back as a reverberation. A component of ASTM C423, Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method, the scale most commonly used to record different levels of sound absorption is the noise reduction coefficient (NRC). NRC ratings range from 0 to 1.0—an NRC of 0 indicates perfect reflection while an NRC of 1.0 indicates perfect absorption.

In actuality, NRC is the average of four sound absorption coefficients of the particular surface at specific frequencies of 250, 500, 1000, and 2000 Hz. These are the typical frequencies of human speech, and, therefore, NRC provides a standardized, simple quantification of how well the particular surface will absorb the human voice. A broader frequency range should be considered for applications where louder sounds, such as music or mechanical noise, are expected to be regularly present. Acoustical building product manufacturers sometimes report NRC values higher than 1.0 for highly absorptive materials, such as fiberglass ceiling panels. This is because the method used to calculate NRC of these materials does not account for sound diffraction caused by the sides of the test panel, which can raise the NRC above 1.0.

Sound Absorption Average (SAA) is another single number rating of sound absorption defined in ASTM C423 and it also ranges from 0.0 to 1.0. SAA is the arithmetic average of the sound absorption coefficients from 200 to 2500 Hz, and it is often reported along with NRC for acoustical products.

Wall assemblies that use a single layer of laminated noise-reducing gypsum board have been shown to meet or exceed the acoustical performance of assemblies that use double layers of traditional gypsum board.

Wall assemblies that use a single layer of laminated noise-reducing gypsum board have been shown to meet or exceed the acoustical performance of assemblies that use double layers of traditional gypsum board.

Healthcare facilities
Healthcare facilities are under constant pressure to provide a pleasant, quiet, and calming interior environment that supports faster healing. Hospitals designed and constructed with reduced noise levels typically experience higher patient satisfaction due to the more comforting environment and improved sleep. These factors can lead to quicker healing times, which can mean shorter stays and reduced costs for both patients and hospitals. From a hospital employee perspective, a low-noise environment can increase job satisfaction, which could reduce employee turnover.

Prolonged healing
Noise stimuli in critical care units have been associated with physiological stress in patients, and those who undergo surgery are more likely to suffer surgical site infections (SSIs) if the operating room is too noisy.1 Acoustic control is also important for patient rooms, as too much noise can disturb sleep, also prolonging recovery. The noise levels of some hospitals well exceed World Health Organization (WHO) guideline values of 35 dB during the day and 30 dB at night in patient rooms, with recommended nighttime peaks of 40 dB. One 2012 study done by the University of Chicago’s Pritzker School of Medicine found peak noise levels in patient rooms often approach 80.3 dB—the same noise level produced by a chainsaw.2

Increased health problems
Patients exposed to continuous noise have been shown to experience anxiety, higher blood pressure, memory alteration, increased agitation, less pain tolerance, and even increased cholesterol. Noise above 50 dB increases the need for analgesia in postoperative patients.3

Compromised speech privacy
Speech privacy between patients and their doctors is critical, especially with today’s federal healthcare regulation requirements. For instance, the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule provides federal protections for personal health information held by covered entities and gives patients an array of rights with respect to that data. Insufficient acoustic control in patient rooms can compromise speech privacy, which can lead to legal trouble for the healthcare facility.

Increased medical errors
High noise levels in healthcare environments have shown to have adverse physiological and psychological effects on patients and cause critical care personnel to be more error-prone.4

The construction and remodeling of healthcare facilities is guided by various contemporary building standards, all designed to make sure patients receive the best environment for healing. Again, acoustical requirements play an important role, especially in HIPAA, the acoustics section (i.e. 807) of the International Green Construction Code (IgCC), and the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) for Healthcare program.

Another standard, Sound and Vibration Design Guidelines for Health Care Facilities, currently in development under the auspices of American National Standards Institute (ANSI) and the Acoustical Society of America (ASA), has already been designated as the sole reference standard for acoustics by the Facility Guidelines Institute with a mission of promoting consensus-based guidelines, advised by research, to advance quality healthcare. LEED 2009 for Healthcare also relies on this standard to demonstrate performance and earn up to two acoustic credits. The standard itself includes design guidelines for sound isolation between various types of rooms.

Acoustic control in schools
With schools, it is imperative for designers to create an effective learning environment, characterized by clear communication between teachers and students. Ambient noise (e.g. conversations in hallways, sound systems, neighboring classrooms, and mechanical equipment) can easily distract students and interfere with communication.

STC suggestions for space adjacencies in a healthcare project.

STC suggestions for space adjacencies in a healthcare project.

Excessive ambient noise also may cause teachers to raise their voices, which further increases the noise level and can cause vocal strain for the teacher. Concerns like these have inspired more stringent school acoustical requirements for both new construction and remodels from leading building standards.

USGBC has been a strong leader for the promotion of highly sustainable school environments through its LEED for Schools program. Within that specialized version of the rating system, acoustic performance is a specific criterion in two cases. First, there is mandated Indoor Environmental Quality (EQ) Prerequisite 3, Minimum Acoustical Performance. The stated intent is:

to provide classrooms that are quiet so that teachers can speak to the class without straining their voices and students can effectively communicate with each other and the teacher.

While this might seem a basic and commonly achieved criterion, the built condition of many school buildings indicates otherwise. Beyond the basic prerequisite requirement, there is also an additional Indoor Environmental Quality (EQ) Credit 9, Enhanced Acoustical Performance, which intends:

to provide classrooms that facilitate better teacher-to-student and student-to-student communications through effective acoustical design.

Simply put, it acknowledges the design efforts of improving acoustical design beyond the minimum prerequisite level to achieve better environments for speech communication and education.

Noise levels and reverberation
Noise levels and reverberation times in learning spaces can cause speech to be unintelligible even after the noise source has ceased. This can affect attention spans and academic performance of students.5

Federal regulations and building standards
The 1990 passage of the Americans with Disabilities Act (ADA) intensified the focus on removing acoustical barriers in educational settings. ANSI S12.60-2002, Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, was approved in 2002.

Non-native languages
Students learning in a non-native language comprise a significant portion of North American classrooms and require more favorable signal-to-noise ratios than students learning in their first language.6

Acoustic control with noise-reducing gypsum board
Designing wall assemblies with various strategically placed layers and materials to achieve the desired STC ratings for a space has been a common practice over the years, but the approach has had its hits and misses. Installing sound-deadening fiberglass insulation between framing is certainly helpful when properly done. The use of multiple layers of gypsum board, sometimes installed over sound-dampening metal resilient channels or isolation clips, can be effective, but it is often costly and problematic.

Incorrect placement of the boards or improper installation of the resilient furring channels and isolation clips can compromise the wall assembly’s sound-containment abilities. Additionally, these configurations increase the wall footprint, reducing the usable area of the floor plan. One contemporary solution to these problems is laminated noise-reducing gypsum board.

The high acoustic performance of laminated noise-reducing gypsum boards enables walls to be built with less material, gaining valuable square footage, and saving both construction time and material cost. Pairing them with a layer of fiberglass batt insulation will further improve on the wall assembly's STC rating.

The high acoustic performance of laminated noise-reducing gypsum boards enables walls to be built with less material, gaining valuable square footage, and saving both construction time and material cost. Pairing them with a layer of fiberglass batt insulation will further improve on the wall assembly’s STC rating.

Intended as a replacement for some of the traditional acoustic control methods on interior walls and ceilings, laminated noise-reducing gypsum board is a single-panel product containing a viscoelastic polymer middle layer applied between two specifically formulated thin layers of gypsum board. The final product ends up being 12 to 16 mm (1/2 to 5/8 in.) thick—the same as traditional gypsum board thicknesses. It can be used for new construction or renovations over both wood and steel framing.

This building product has the ability to dampen sound transmission by using the inner polymer layer as a kind of shock absorber that slows board vibrations, dissipating the sound energy into thermal energy. Additionally, it performs well acoustically over an extended range of frequencies, resulting in increased STC ratings for the assemblies. Specification of noise-reducing gypsum board is thus a suitable method for meeting STC requirements without complex techniques.

Isolation clips and resilient furring channels can easily be short-circuited during the construction process. Interferences with their performance can also take place during picture-hanging or pressing of heavy objects against the wall. These risks are eliminated when using noise-reducing gypsum board directly applied to framing thus providing more consistent and predictable acoustic performance.

The material can still be used in wall assemblies where resilient channels or clips are desired to achieve extra sound transmission control. In this case, the gypsum board helps reduce the negative effect of any short circuits.

Employing the specialized products can also help reduce material usage versus traditional multi-layered gypsum systems that might be otherwise required to achieve high sound attenuation. The high acoustic performance makes it possible to build effective noise-reducing walls with less material, gaining valuable square footage, and saving both construction time and material cost. Less material used also means a more sustainable structure in keeping with green building practices.

Assemblies employing a single layer of laminated noise-reducing gypsum board have been tested and shown to meet or exceed the acoustic performance of assemblies using double layers of traditional gypsum board. In fact, these boards have been shown to increase the wall assembly’s STC rating by 10 or more points, while adding an extra layer of traditional gypsum board increased STC by two to three points. This makes it quite effective in situations where acoustic management is needed to dampen sound energy and significantly improve sound attenuation through walls and ceilings.

However, laminated noise-reducing gypsum board is not very effective for low-frequency airborne sound. Typically, commercial projects use laminated noise-reducing board for all interior walls, along the perimeter and the partitions of a space. It is used in living and working spaces, as well as mechanical and utility spaces.

Specifying noise-reducing gypsum board
In writing specifications for noise-reducing gypsum board, the first thing to determine is the required sound rating for the assemblies incorporated into the building and design them accordingly. The following options can then be considered:

  • 13 or 16-mm (1/2 or 5/8-in.) thick Type X gypsum board;
  • 102-mm (4-in.) widths, 203-mm (8-in.) or custom lengths;
  • tapered edges; and
  • products meeting ASTM C1396, Standard Specification for Gypsum Board,, and ASTM C1629, Standard Classification for Abuse-resistant Non-decorated Interior Gypsum Panel Products and Fiber-reinforced Cement Panels.

Noise-reducing gypsum board is installed following traditional methods of application and finishing of interior gypsum board products for both walls and ceilings, but with a little more attention to detail to ensure acoustic performance. First, the board layout should stagger joints from one side of the wall to the other. Then, sound-insulating fiberglass batts can be installed in wall cavities for higher STC ratings where needed.

It is appropriate to specify putty pads—tested per ASTM E90, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements—or acoustical sealant to seal electrical outlets and switch cutouts.

Consisting of a viscoelastic polymer applied between two specifically formulated thin layers of gypsum board, these products dampen sound waves that attempt to pass through the wall assembly, impeding sound transmission.

Consisting of a viscoelastic polymer applied between two specifically formulated thin layers of gypsum board, these products dampen sound waves that attempt to pass through the wall assembly, impeding sound transmission.

Panels of noise-reducing gypsum board should be installed in accordance with standard Gypsum Association (GA) 216, Application and Finishing of Gypsum Panels (ASTM C840, Standard Specification for Application and Finishing of Gypsum Board) and the manufacturers’ application instructions. Best practices call for a 6-mm (1/4-in.) gap around all wall perimeter edges to allow for any movement.

Noise-reducing gypsum boards are typically cut the same as other gypsum board by deeply scoring from both sides and snapping. Cutting across a 1.2-m (4-ft) width may require use of a hand or power saw. One should specify an acoustical sealant to seal the 6-mm perimeter gaps and wall penetrations per ASTM C919, Standard Practice for Use of Sealants in Acoustical Application.

Noise-reducing gypsum board may be finished, painted, or wallpapered using conventional techniques. GA-214, Recommended Levels of Gypsum Board Finish, should be referenced when specifying the level of finishing desired.

Conclusion
As an added advantage, most of today’s noise-reducing gypsum boards also have moisture- and mold-resistant face and back papers; many offer an economical single-layer alternative to multi-layer gypsum board configurations in wall and ceiling assemblies. The result of this combination is improved sound attenuation for high-STC assemblies in various building settings, protection against mold growth, and an important role in ensuring optimal indoor environmental quality. Noise-reducing gypsum boards are a very practical choice for a wide variety of projects, where they will likely soon become the norm, rather than the exception.

Notes
1 For more, see see the article, “Adverse Effect of Noise in the Operating Theatre on Surgical-site Infection ,” by A. Kurmann et al, which appeared in the July 2011 International Journal of Cardiology. (back to top)
2 See Jordan Yoder et al’s “Association Between Hospital Noise Levels and Inpatient Sleep Among Middle-aged and Older Adults: Far from a Quiet Night,” from the January 2012 edition of Archives of Internal Medicine. (back to top)
3 See C. Cmiel et al’s “Noise Control: A Nursing Team’s Approach to Sleep Promotion: Respecting the Silence Creates a Healthier Environment for Your Patients“ in the February 2004 American Journal of Nursing. (back to top)
4 For more, see I. Busch-Vishniac et al’s “Noise Levels in Johns Hopkins Hospital,” published in the Journal of the Acoustical Society of America (118[6]). (back to top)
5 This comes from ASA’s “Tech Paper 133,” published in 2005. (back to top)
6 See the 2005 American Speech-Language-Hearing Association technical report. (back to top)

Ashwin L. Himat is the director of marketing for CertainTeed Gypsum. Involved with launching new gypsum products, he has almost 20 years of experience working for Saint-Gobain Corporation and its subsidiaries. Himat received the 2011 Wall Street Journal Technology Innovation award in the ‘environmental’ category for work with formaldehyde-absorbing gypsum. He can be reached at ashwin.l.himat@saint-gobain.com.

Security Glazing for Safer Schools: Trends in School Safety

Between 1999 and 2009, various school security measures have been implemented:

  • controlled access to the building during school hours (moving from 75 to 92 percent in that decade);
  • controlled access to school grounds during school hours (34 to 46 percent);
  • identification badges for faculty (25 to 63 percent);
  • video cameras to monitor school (19 to 61 percent);
  • telephones in classrooms (45 to 74 percent);
  • student uniforms (12 to 20 percent);
  • restricted social networking websites (now 93 percent); and
  • restricted cell phone use during school hours (now 91 percent).

To read the full article, click here.

 

Security Glazing for Safer Schools

Photo courtesy Graham Architectural Products

Photo courtesy Graham Architectural Products

by Julie Schimmelpenningh

With recent tragedies involving school shootings, parents and administrators across the country are demanding ways to make K−12 facilities more secure. Areas of the schools under significant scrutiny are doors and windows—and more specifically, the glass being specified.

For extra school security, laminated security glass can be an easy and cost-effective measure to assist in resisting forced entry and the threat of bullets. Compared with traditional annealed or tempered glass, this type of material can secure the building more effectively.

Laminated glass is made from a tough plastic interlayer bonded between two pieces of glass. The interlayer is invisible to the naked eye, so laminated glass offers the same clear visual benefits as ordinary glass—an important feature for security. From inside, glass allows occupants to see someone approaching the school. From the outside, it can help responders locate intruders or victims.

Success in other fields
Laminated glass has successfully protected public facilities and major works of art for many years. Security glass has been in use in various forms for generations. Invented in 1903 by French chemist Edouard Benedictus, laminated glass has been employed for decades in car windshields to greatly reduce injuries. It is commonly used in high-risk facilities such as embassies and federal buildings, as well as museums. Laminated glass protects great treasures such as the Mona Lisa, the U.S. Constitution, and the Crown Jewels in London.

After the devastation caused by Hurricane Andrew in 1992, laminated glass became the standard in Florida and other coastal regions. Building code requirements were established to lessen the amount of destruction caused from high winds and to ensure occupant safety.

Enhancements to laminated glass configurations ensure glazing in federal and other public buildings are blast-resistant. Dozens of lives were saved by blast-resistant laminated glass when the Pentagon, newly remodeled, was attacked on September 11, 2001. The shockwaves following an explosion can send glass shards flying for miles and generally cause about 70 percent of the injuries following a blast, as was the case in the 1995 Oklahoma City bombing and many other blast events. It is these qualities that make the material a good candidate for school specifications.

When remodeling an educational facility or building a new school, security should be a major player in the design process. Windows and doors are the easiest point of entry into a school, but they don’t have to be.  Installing laminated security glass for all windows and doors makes forced entry much more difficult. Images courtesy Eastman Chemical Company

When remodeling an educational facility or building a new school, security should be a major player in the design process. Windows and doors are the easiest point of entry into a school, but they don’t have to be. Installing laminated security glass for all windows and doors makes forced entry much more difficult. Images courtesy Eastman Chemical Company

Renewed need for extra security
A school is more than just a facility; it is a place where families send their kids for the majority of their day to learn, participate in sports and clubs, and perform in musicals and plays. Schools can be why families buy a home in a specific neighborhood, and they can be what ties a community together—the buildings are frequently used as emergency management centers or shelters in times of crisis, making security an important attribute, even after teaching hours.

In recent years, however, schools are not being thought of as the safe havens they once were. Since 1992, there have been 387 shootings in U.S. schools, according to www.stoptheshootings.org. One of the most recent involving fatalities occurred last December at Sandy Hook Elementary School, where 20 children and six adults were killed. As no one can predict whether an attack will happen, it is important schools be prepared for anything.

Immediately following the Sandy Hook shooting, discussions across the country started about how this tragedy and future shootings could be prevented. There were conversations about gun control, awareness and care for the mentally ill, as well as improving safety at schools through better communication systems, security measures, and intruder drill training. School districts everywhere are looking at how they can keep their students, teachers, and faculty safe. Design/construction professionals can play an important role as well.

What the school construction industry can do
By installing laminated security glass for all windows and doors, forced entry becomes much more difficult. Laminated glass is fabricated with a tough, protective interlayer, typically of polyvinyl butyral (PVB), which is bonded with heat and pressure between two pieces of glass. The use of thicker interlayers can increase the resistance of the glass to impacts. Upon impact, laminated glass will shatter, but glass shards remain held together by the bonded interlayer. Risks associated with flying or falling glass are minimized.

Laminated security glass stands up to multiple assaults from a blunt or sharp object used to gain entry. If an intruder tries to break through a window or the glass lite of a door, it would take several blows before he or she achieves access through the security glass. This allows valuable time for anyone inside the school to react, enabling more opportunity to call the police, send internal communications about the intruder, lock-down interior doors or classrooms, evacuate, or move students to a safer area.

From a glazing standpoint, school architects and administrators may consider the following when designing new or retrofit glazing systems:

  • glass should provide inherent health, safety, and security benefits that can help mitigate disasters;
  • natural daylight is essential for psychological benefits of students and teachers;1
  • glass should provide visibility for critical passageways and entry areas; and
  • sustained functionality—basic functions of the school can operate following a natural disaster or incident.

Considering threat levels
Entry doors have been the most vulnerable in many school shootings. Hurricane-rated high-impact (i.e. large-missile) glass, or even ballistic glass should be considered. As in the case of Sandy Hook, the shooter penetrated the side lite of the door and then reached through to open it. The ‘break-and-reach’ ability of the intruder must be delayed or stopped. High-performance glass provides resistance, while still providing much needed visibility.

Existing doors may need to be replaced completely if bullet-resistant glazing is specified, as the framing system for such heavy configurations is specialized.

Access doors with a double-entry lobby to the school should be equipped with laminated security glazing having forced entry/burglary resistance capability in accordance with Underwriters Laboratories (UL) 972, Testing for Burglary-resistant Glazing Materials, or Class I of ASTM F1233, Standard Test Method for Security Glazing Materials and Systems.

Today’s schools have an increasing amount of glass windows and doors because of the positive benefits it brings. For extra security, laminated glass is an easy, cost-effective measure in protecting against forced entry and bullet resistance. Compared with traditional annealed or tempered glass, laminated glass can secure the building more effectively.

Today’s schools have an increasing amount of glass windows and doors because of the positive benefits it brings. For extra security, laminated glass is an easy, cost-effective measure in protecting against forced entry and bullet resistance. Compared with traditional annealed or tempered glass, laminated glass can secure the building more effectively.

First-floor glass should be, at a minimum, equipped with basic laminated glass, which typically requires a 0.76-mm (0.03 in.) thick interlayer. This type of glass will deter ingress, retain glass, and slow break-and-reach attempts. Forced ingress glazing will offer greater protection, and uses a thicker interlayer. Laminated glass can be retrofitted into most existing window and door systems and can contribute to compliance for security windows per ASTM E2395, Security Performance of Window and Door Assemblies With and Without Glazing Impact.

If budgets do not permit replacement of windows, security film can be post-applied over the existing windows and doors. This option offers some of the benefits of laminated glass, but provides less resistance against an intruder. Further, like other laminated glass options that are not ballistics-resistant, it will not stop a bullet. Security film also modifies the post breakage behavior of glass, but may allow time to take additional action versus non-enhanced glazing.

During new construction, laminated glass may make economic sense due to its higher performance levels. However, post-applied films can be a good alternative in a retrofit situation where glass replacement is not possible.

It requires several shots from handguns like a 9 mm, .357, or .45 caliber to make a hole large enough to put a fist through to unlock a door or window. In some cases, the intruder may be temporarily confused, as the glass does not ‘behave’ as expected. There are many documented smash-and-grab attempts at a burglary where would-be intruders give up because they are generating too much noise and attention.

Additional benefits
Along with its safety and security enhancing features, laminated glass offers other benefits for schools. Laminated glass dampens sound coming in from the outside, making it an ideal choice for schools located in noisy neighborhoods or urban environments. The interlayer in laminated glass significantly dampens sound, keeping unwanted outside noise at bay.

Numerous studies have shown children concentrate and can learn better in a quiet space. For example, one research project found links between higher achievement and less external noise. Excessive outside sound resulted in increased student dissatisfaction with their classrooms and stress.2

Laminated glass also reduces the amount of solar heat gain and ultraviolet (UV) rays going into a building, making it more comfortable and healthy for students and teachers. Work has been done delving into the importance teachers place on thermal comfort, proving temperature affects both teaching quality and student achievement.3 Interestingly, studies in the 1970s found the best temperature range for learning math and reading is between 20 and 23 C (68 and 74 F).4 Maintaining a specific classroom climate is an essential part of setting students up for success.

CS_February_2014.inddHurricane-rated laminated glass protects against natural disasters. Following Hurricane Andrew in 1992, Florida began to strengthen its building codes to help protect the building envelope. Windborne debris was a major problem during this Category 5 hurricane, and the construction industry began to look for ways to protect the windows in commercial buildings and schools.

Laminated glass proved to be one of the most effective solutions for this problem, and today, is commonplace in buildings in coastal areas of the United States, the Caribbean, and other world areas. Hurricane-resistant glass comprises multiple interlayers; it can be considered for vulnerable areas of a school, such as entry and rear doors, sidelites, and floor-to-ceiling windows.

Laminated glass is versatile, readily available, affordable, and easy to install. Also, it can be used to help a project earn credits within the U.S. Green Building Council (USGBC) Leadership in Energy and Environmental Design (LEED) program. Specifically, designers can secure points toward LEED certification under

  • Energy & Atmosphere (EA) Credit 1, Optimize Energy Performance;
  • Materials & Resources (MR) Credit 4, Recycled Content;
  • Indoor Environmental Quality (EQ) Credit 8, Daylight & Views; and
  • EQ Credit 9, Enhanced Acoustical Performance.

Since laminated glass offers solar, safety, and acoustic benefits, it can help achieve points ordinary glass may not.

Upgrading schools through glazing
In 1998, data collected in surveys conducted by the National Center for Educational Statistics (NCES) suggested the average public school building in the United States was 42 years old.5 This suggests many of the country’s schools may now be at an age where frequent repairs are necessary.

Due to the burst in school construction during the Baby Boom Era, the NECS study reports almost half (i.e. 45 percent) of schools were built between 1950 and 1969. Seventeen percent of public schools were built between 1970 and 1984, and only 10 percent after 1985. These older schools were not envisioned with modern-day security and safety measures in mind; further, they do not offer the physical security level now desirable.

Educator A.C. Ornstein found by the time school is 20 to 30 years old, frequent replacement of equipment is needed.6 Original equipment, including roof and electrical systems, should be replaced between 30 and 40 years old, as rapid deterioration begins after this point. In fact, most schools are abandoned by the time they reach 60 years.

When the NECS study was published, most of those facilities were already about 50 years old and experiencing serious decline. In other words, half of the country’s public schools could be seen as major threats to student safety.

Immediately following the Sandy Hook shooting, discussions across the country started about how this tragedy and future shootings could be prevented. School districts everywhere are looking at how they can keep their students, teachers, and faculty safe. Design and construction professionals can play an important role as well.

Immediately following the Sandy Hook shooting, discussions across the country started about how this tragedy and future shootings could be prevented. School districts everywhere are looking at how they can keep their students, teachers, and faculty safe. Design and construction professionals can play an important role as well.

Today, as the rate of school construction continues to decline, safety is a more serious concern than ever. The existing stock of schools is too old to offer any kind of reliable security systems. Outdated glass, in particular, lacks basic insulation features to control classroom temperature and cannot offer much more than protection from outdoor elements. However, the installation of laminated glass immediately updates an aging school and offers protection to students and teachers.

While there is pressing need for building better schools, many face funding and time constraints. When new buildings cannot be erected, the architectural community must look at available options to modernize, update, and safeguard existing schools. Laminated glass or window film remains one of the easiest and most cost-effective measures available for enhancing student and faculty safety.

Notes
1 For example, a 2002 study by L. Heschong et al (“Daylighting Impacts on Human Performance in School,” Journal of the Illuminating Engineering Society, 31[2])identified effects of natural light on students as evidenced in significantly improved standardized test scores for elementary students. The same study concluded that daylight contributed positively to overall health and well-being of students. (back to top)
2 The G.I. Earthman and L. Lemasters’ paper, “Where Children Learn: A Discussion of How a Facility Affects Learning,” was presented at the 1998 annual meeting of Virginia Educational Facility Planners. (back to top)
3 The 1999 J.A. Lackney report, “Assessing School Facilities for Learning/Assessing the Impact of the Physical Environment on the Educational Process,” was published by Mississippi State’s Educational Design Institute. (back to top)
4 The David P. Harner article, “Effects of Thermal Environment on Learning Skills,” appeared in Educational Facility Planner, 12 (2). (back to top)
5 The NCES report, “How Old Are America’s Public Schools?” was published in January 1999 by the U.S. Department of Education’s Office of Educational Research and Improvement. It can be read online at nces.ed.gov/pubs99/1999048.pdf. (back to top)
6 Ornstein’s article, “School Finance and the Condition of Schools,” appeared in the book, Teaching: Theory into Practice (Allyn and Bacon). (back to top)

Julia Schimmelpenningh is global applications manager, advanced interlayers for Eastman Chemical Company. She is has been a glass industry activist for 25 years with experience in research and development, technical lamination processing, product, applications, and standard development. Schimmelpenningh is a participating member of ASTM, International Organization for Standardization (ISO), and Glass Association of North America (GANA). She can be reached at jcschi@eastman.com.

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