High-Performance Glass Solutions  

In our modern world, designing, specifying, and constructing high-performance buildings is no longer optional. Rigorous building codes require it. Owners and occupants increasingly demand it. And our global sustainability depends on it. “Anyone who can see the data on climate can see that something has to change when it comes to carbon emissions,” says Josh Wignall, director of marketing for EFCO Corp. “And we need to do it quickly.”

All images courtesy of National Glass Association

MEC Headquaters in East Vancouver, British Columbia, Canada

Increased carbon in the atmosphere leads to climate change, which causes drastic temperature fluctuations, droughts, severe tropical storms and hurricanes, and rising sea levels. Intense storms, heat waves, driving rain, and heavy snow can wreak havoc on building exteriors, leading to unwanted air and water intrusion that can cause a building’s materials to decay at a much faster rate. Unwanted heat gain and loss can also be problematic, creating higher energy costs and putting more strain on the mechanical system, which will then use more energy, generate more greenhouse gases, and perpetuate the cycle of climate change.

Glass facades, as well as their framing systems, are part of the building envelope, which is the first line of defense on a structure. In the past, glass was not ideal for large expanses of buildings because it did not provide insulating properties that could prevent unwanted solar heat gain or loss. Older buildings often have smaller windows and solid doors instead of full facades made of glass and glazing. Thanks to the advancements in glass technology and glazing, glass is now much more energy efficient. By treating large glass expanses and the framing as part of the entire building system, architects and installers can ensure that glass and glazing contribute to the high performance of buildings rather than detracting from it.

Introduction to Glass, Glazing, and the Systems Approach

When specifying glass, architects and designers must consider many factors in addition to energy efficiency and thermal protection. These include safety, security, and proper daylighting for occupants.

Glass

First, let’s introduce some common glass types and their applications. We will discuss annealed glass, heat-strengthened glass, tempered glass, and safety glass.

Annealed Glass

Annealed glass is popular in residential construction and sometimes used in commercial construction applications. Annealed glass is cooled slowly to prevent any residual stress in the body of glass. It can be cut, machined, drilled, edged, and polished, unlike tempered or heat-strengthened glass.

Heat-Strengthened Glass

Heat-strengthened (HS) glass undergoes heating and cooling processes in manufacturing, making it twice as strong as annealed glass of the same thickness and configuration. According to ASTM C 1048, heat-strengthened glass must have a surface compression between 3,500 and 7,500 psi for a thickness of up to 6 millimeters. Due to its greater resistance to thermal loads (when compared to annealed glass), it can resist most wind and thermal stress loads.

When HS glass is broken, the fragments are typically larger shards and may remain in the glazing opening. Large broken shards can cause injury to occupants, therefore HS glass is not a safety-rated glazing, as specified by ANSI Z97.1 and CPSC 16 CFR 1201. Because it can withstand wind load and thermal stress, HS glass is intended for general glazing and is often used in commercial applications. HS glass cannot be cut or drilled after heat strengthening.

Fully Tempered Glass

Tempered glass undergoes a thermal tempering process and is approximately four times stronger than regular annealed glass of the same thickness and configuration, making it ideal for commercial applications. Per ASTM C 1048, the surface compression of fully tempered glass must be 10,000 psi for thicknesses up to 6 millimeters. When fully tempered glass passes ANSI Z97.1 and/or CPSC 16 CFR 1201, it is often referred to as a “safety tempered glass” because it meets the requirements of various code organizations for safety glazing. If fractured, the glass will break into smaller pieces, making it less likely to cause serious injury in most applications.

Next we will discuss various types of safety glass, including monolithic safety tempered glass, single lite with film/plastic, laminated, laminated insulating glass units (IGUs), and multi-ply.

Illustration of tempered glass

Monolithic Safety Tempered Glass Lite

Monolithic safety tempered glass is a single glass lite but also safety tempered. Safety tempered glass is approximately four times stronger than regular annealed glass and called “safety glass” because, when fractured, it breaks into smaller pieces, which makes it less likely to cause serious injury. Monolithic safety tempered glass is also great for daylighting because it allows sunlight to penetrate the building. This glass is best suited for areas that require safety glazing per IBC Chapter 24.

Single Lite with Film/Plastic

A single glass lite with an applied film or plastic that passes the ANSI Z97.1 and/or CPSC 16 CFR 1201 testing is also considered safety glazing because it will break and be contained in the glazing opening. A single glass lite with film or plastic will also allow for proper daylighting. This glass is more secure than standard single safety tempered glass lites.

Illustration of single-lite glass with film or plastic

Laminated Glass

Laminated glass is made up of two or more lites that are permanently bonded under heat and pressure with one or more plastic interlayers to provide extra protection. This type of glass is great for areas that need added protection, such as entry doors or glass areas in banks, waiting areas, or other public spaces where safety is a concern. Another safety feature is that, when broken, the glass stays contained instead of vacating the glazing opening. This is especially important in the event of forced entry or weather events that could cause flying debris. In addition to safety, laminated glass provides enhanced acoustics by keeping sound in areas where it belongs and out of places where it does not belong. It also provides daylighting for areas where glass may not have been an option before.

From left: illustrations of tempered glass, film or glass clad plastics, and the layers that make up laminated glass

Laminated Insulating Glass Unit (IGU)

Laminated glass within an insulating glass unit (IGU) provides all the benefits previously discussed for laminated glass but with the added benefit of energy efficiency and resistance to adverse weather. Laminated IGUs are also made up of two or more lites that are permanently bonded under heat and pressure with one or more plastic interlayers. However, laminated IGUs provide an extra layer of protection thanks to the spacer placed between the two lites. Sometimes laminated IGUs are comprised of two laminated pieces of glass, and other times it is a single lite with a spacer and then laminated glass on the other side. This space between the two lites provides extra thermal protection and can limit unwanted heat transfer. This type of glass can also protect against wind-driven debris impact from strong storms, such as hurricanes.

Illustration of layers that make up a laminated insulating glass unit (IGU)

Multi-Ply Glass

Multi-ply glass is a high-quality glazing configuration that contains multiple interlayers and/or plastic glazing for added protection to withstand extreme conditions, including forced entry, blasts, ballistics, hurricanes, and tornadoes. Like laminated glass, it can also provide enhanced acoustics, keeping sound in areas where appropriate and out where not appropriate. It can also provide daylighting options for secure areas that may not otherwise have the option for daylighting if, say, the area were surrounded by a concrete wall for protection.

Illustration of multi-ply glass

Whether it is added protection or lower cost, there is a type of glazing for every application that can provide benefits to the building owner. By specifying a combination of various glazing types for specific applications, architects and specifiers can create a solution that is best for all.

Understanding Performance and Payback

With all the glass and glazing options out there, one has to wonder, why is the latest and greatest technology not being used to its fullest potential on every project?

Glass and glazing industry experts point to a range of hurdles that stand in the way of performance, including cost, and outline the opportunities for payback in terms of people, energy costs, and more.

Perhaps the biggest roadblock to high-performance building design and construction is cost, say industry officials. To overcome this hurdle, the industry as a whole (including manufacturers, specifiers, builders, and building owners) must commit to achieving high levels of thermal performance so that occupants can see an increase in energy cost savings.

High-performance glass and glazing products are often taken out of projects due to higher upfront costs, sources say. “Specs often start off with high-performance systems. Design teams are interested in high-performance systems, but because of cost, they are value engineered out,” says John Cox, project executive, Giroux Glass.

The glass and glazing industry is ready to help architects bring their projects—new and old—to the next level of building performance. While the industry has the technology, it is up to specifiers and consumers to prioritize this technology when planning and constructing high-performance buildings.

To achieve high-performance targets, jurisdictions must adopt and enforce the newest, more stringent energy codes, project teams must work collaboratively to design and construct buildings that meet performance goals, and team leaders and building owners must prioritize performance and be willing to invest in available solutions.

“There are systems on the market that can meet the most stringent energy requirements. They are just not being used,” adds Helen Sanders, strategic business development, Technoform.

Architects and specifiers can address these challenges when presenting glass and glazing options to their clients by providing solutions in regard to long-term savings as well as occupant comfort.

Paybacks and Cost Savings

When it comes to cost savings, glass and glazing companies have developed a range of high-performance solutions that are achievable and affordable. “With a high-performance thermally broken window and curtain wall system, and good edge-of-glass [performance], you can achieve a good U-factor using standard low-e. You can do it. You just need to know what is available,” says Technoform’s Sanders.

To keep costs down, Alissa Schmidt, technical resources manager, Viracon, recommends that architects “stay within the realm of typical 1-inch insulating glass systems and stay within an average module size. Not varying systems, not going with unique shapes, can help with pricing,” she says. For glass coatings, she recommends designers work with suppliers to find the most affordable low-emissivity glass for the project. “Tinted substrates are also an option. There is minimal cost to go with basic tint,” she says.

High-performance facades can translate to lower heating, cooling, and lighting costs while offering improvements for occupants. This is true for new construction and, in particular, retrofits. “It is not a huge investment to update the envelope. The paybacks can be major. You can improve occupancy comfort, save on your energy bill, and reduce the loads on the air conditioning or heating. This can save a lot of money, and you will see increases in lease rates and property values,” Wignall says.

Performance Perks for Occupants

When comprehensive high-performance glass solutions are specified and installed, occupants also enjoy the benefits of proper daylighting, thermal comfort, security, and safety from intrusions and blasts. When occupants are comfortable, they are healthier, happier, and more productive.

Building occupants are healthier and perform better when they are granted access to views and are comfortable in terms of daylighting levels and temperature. Studies on occupant comfort show increased healing times for patients, improved test scores among students, and decreased absenteeism and increased productivity among office workers. “We cannot underestimate the importance of daylighting and its ability to improve health and happiness within the workplace,” Wignall says. “People cannot sit in a brick box with no light.”

Because people in healthier buildings miss fewer days of work, perform tasks more efficiently, and stay in their jobs longer, owners and employers can see notable paybacks. Employers see productivity improvements and building owners can charge higher lease rates.

Too often, building managers and owners do not factor people into the building performance equation. However, it is the people who represent the costliest aspect of running a building, says Stephen Selkowitz, former senior advisor for building science, and former group leader of the Windows and Envelope Materials Group in the Building Technology and Urban Systems Division of Lawrence Berkeley Lab. He estimates that occupancy costs reach about 100 times the cost of energy.

Although building occupants need access to daylighting and views, too much daylight leads to glare and heat gain, which negates the potential occupant comfort benefits. “One of the biggest misconceptions I see is the automatic, if not subconscious, assumption that all-glass facades lead to better daylight and views,” says Galen Burrell, director of lighting design at View Inc. “However, the reality is that there can be too much of a good thing, and so we should focus on optimizing daylight rather than maximizing it. Unchecked sunlight can create various comfort issues associated with excessive glare and heat. As a result, blinds get closed and generally remain closed, and the entire value proposition of daylight and views get lost.”

Taking a "Systems" Approach When Specifying Glass, Glazing, and the Rest of the Facade

While high-performance glass and glazing can help reduce long-term heating, cooling, and lighting costs, it is important to recognize that specified glass is part of a larger system that includes the framing, the facade, and even the mechanical and lighting systems. When specifying glass, the system must be viewed as a whole to ensure that glass and glazing solutions not only provide proper daylighting and lower energy costs but are also aesthetically pleasing and designed to work with new or existing mechanical and lighting systems.

The biggest misconception in glazing system performance is that it is all about the glass. Performance values for the glass must be considered in concert with values for the framing system to develop whole-system performance values. “To many, glass seems to be the most obvious factor in performance, but the opposite is true,” says Anthony Intintoli, architectural sales representatives for YKK AP. “You have to find the right glazing system and framing system to achieve the desired high performance.”

At times, performance and aesthetic goals are at odds on projects. In recent years, this has been the case with trends toward ultra-clear, less-reflective glasses that can create challenges with solar heat gain and glare. “This is a big hurdle when it comes to glass performance,” says Viracon's Schmidt. “It is important to work with glass suppliers to find a compromise. How much are you willing to sacrifice in terms of appearance to achieve performance goals? We can come up with solutions for a building that meets renderings but still performs.”

Thermal Protection Through Glazing and Framing

Center-of-glass (COG) thermal performance values, U-factors, cannot be used alone to determine the performance of a complete glazing system. “The COG U-factor makes up only part of a window’s performance,” says Technoform’s Sanders. “It is necessary to look more broadly at the window system, including the edges: the frame and edge of glass. You can have a great center of glass value, but if you do not match that with thermal performance in the framing or edge of glass, you are going to have other performance issues, such as condensation or thermal discomfort.”

Framing systems are designed to meet different structural, water, and air performance requirements depending on their application. These differences translate to varying high-performance methods and thermal performance targets. For example, curtain wall systems can be made wider, thus allowing for improved thermal elements such as multi-cavity insulating glass units, or larger and more complex thermal breaks. “With a storefront, you are typically not going to achieve the performance as you would with a curtain wall,” says EFCO’s Wignall. “You usually see pour and debridge thermal breaks in storefront; you will typically have fewer opportunities for glass in terms of thickness.”

Misconceptions about glass and glazing performance, lack of high-quality modeling, and a siloed approach to design and construction all impede performance goals. To meet and exceed expectations, industry experts recommend project teams clearly understand the various performance values of glass, consider the relationship between the glazing and the rest of the facade, ensure correct modeling from the start, and more.

A project can feature the highest-performing glazing system options, but if thermal performance does not carry over to the connection points, the facade will not meet its goals. “We see big issues around the interfaces,” says Sanders. “This is where the thermal bridging happens.”

To tackle the problem, Sanders recommends project teams review the details of, and if possible model, the interfaces. “The models have to be well detailed—3D modeling rather than 2D modeling is needed for appropriate accuracy. And, we have to measure the performance—for example, take infrared pictures of the buildings,” she says.

Glass and Glazing Performance as Part of the Facade

Next-level facade and building performance comes when glazing systems are integrated into the full building. “Every building, every facade is going to be different,” says Tom Culp, code consultant for the National Glass Association (NGA) and owner of Birch Point Consulting. “You have to look at everything together—the glazing with the shading. Are you going to incorporate sun shades? Automated blinds? Are you going to do things with a double wall? Are you going to tie in daylighting controls? We have to think more broadly, beyond just two lites of glass.”

Considering Occupants and HVAC Systems

Occupants often stand in the way of performance goals. “On day one, building performance might be perfect. But that can change quickly if people in the building do not understand how it should be used—that is, if they are not operating windows, shading, etc. at the right times,” says Selkowitz. Automated systems that control shading, lighting, HVAC, and more ensure the building performs as it should. However, facility managers as well as occupants should be educated on why the automated systems are working as they are, Selkowitz says.

When calculating system performance values, seek assistance of suppliers. “Many manufac-turers offer advanced thermal analysis to help demonstrate the performance of framing systems,” says YKK AP’s Intintoli.

When completing performance calculations, it is essential to make calculations based on the specific products chosen for the system. Not all systems, despite the similarities, perform alike. “You need to be careful that you are doing good modeling and the actual modeling is featuring the products you are using,” Selkowitz says.

Specifying Protective Glass

While there are glazing options that can provide vital protections against glare and thermal loss, there are also additional ways glazing can provide protection to occupants in our ever-changing world. Specific glass types and glazing can provide added safety protections, such as fire protection as well as intruder and blast protections.

In our modern world, there is a need for protective glazing on glass doors and windows to keep occupants safe. This is especially true in public buildings and areas where people congregate, such as schools, churches, and government buildings. While it would be great to make every window and point of entry bullet and fire resistant, a common barrier is, once again, cost. In response, the glass industry has developed a range of security glazing solutions that provide forced-entry resistance without the high price of more traditional bullet-resistant products. The products are designed to not only delay a potential intruder until first responders arrive but also provide daily benefits, such as thermal protection, enhanced acoustics, and daylighting.

While protective glazing and security glazing that can frustrate intruders have recently become more popular in public places, fire-rated glazing products and fire-protective glass have been in demand for quite some time. Fire has been a risk to building structures for centuries, and market demand has driven innovative fire-protection technology to ensure occupant safety. In addition, fire-rated glass and glazing solutions are capable of providing additional benefits to occupants, including daylighting and thermal performance.

Product performance, design, weight, cost, and delivery will vary depending on whether a glazing product is fire protective or fire resistive. This begs the question: What’s the difference?

In terms of performance, “fire-protective products limit the spread of fire and smoke. Fire-resistive products also limit the spread of fire and smoke but also act as a barrier to radiant heat,” says Jerry Cucchi of Aluflam.

“The barrier to radiant heat is an important distinction between the two and can have a significant impact on cost and schedule,” Cucchi says. “There are also differences in how the glass options are made and supplied. Fire-protectives are thinner and lighter, and more of a commodity product that can often be sourced from a different supplier than the hollow metal frames. Fire-resistives are thicker and heavy, and supplied as a system—frame and glass—from a single manufacturer.”

The fire-rated glazing market can be a challenging one to navigate. Suppliers continue to push the envelope of what solutions are possible, and codes are consistently being updated, along with adoption and enforcement.

Suppliers recommend that architects seek assistance from fire-rated glazing partners early and often. “To address misconceptions, we stress the importance of involving the manufacturer as early in the design process as possible to avoid issues—design and budget—later on,” says Aluflam’s Cucchi.

Building owners or architects also frequently have questions about the fire rating of a particular application. The rating of a partition or barrier is not determined by the manufacturer but instead by the authority in the building’s jurisdiction. Manufacturers can help provide solutions when given the required specs; however, they are not the ones who can determine if you are meeting code. When selecting a fire-rated product, consider not only the appropriate product for a specific application, but also make sure it will comply with local codes. After you determine which product is most functional, from this category you can determine which will be the most aesthetically pleasing in the application.

Several fire-rated glazing suppliers also offer continuing education opportunities to address market trends, and common questions and concerns.

Fire-Rated Glazing Products Do More Than Protect

These days, fire-rated glazing products do more than protect. Thanks to market demand, the glass industry has developed solutions that satisfy multiple needs, from daylighting to thermal performance to aesthetics. There are many popular trends that have emerged over the years, thanks to the technological developments that have made glass a more viable product for exterior and interior walls.

Fire-rated glass oftentimes needs to support structural loads while also blocking flames, smoke, and heat from fires. But what about also providing additional security against intruders or burglaries? Glass that is multifunctional can provide a high level of fire and life safety while also offering bullet resistance, blast resistance, and resistance against intruders or forced entry. Glass products that can meet these safety and security needs, while also providing an aesthetically pleasing facade, are trending. And this trend does not appear to be slowing down any time soon.

Added security often means adding extra layers or additional materials to glass to make it more durable. Fire-rated glass and security glass is often thicker than standard glass, which can make it really heavy, thus making doors harder to open. To accommodate this, architects and builders must specify upgraded hinges and hardware. Some door manufacturers are looking for lighter-weight options to help this challenge. One solution is fire-rated glass ceramics, which have a lower density than regular soda lime glass. Fire-rated glass ceramic products are trending in doors and other applications where the wall or window needs to move.

Translating Code Requirements to Glazing System Solutions

As technology advances, energy codes are revised and updated to ensure that buildings are not only safe for occupants but also provide as little impact as possible on the environment. High-performance glass and glazing solutions typically meet or exceed energy code requirements and/or health and safety codes and requirements, but it is important to be aware of the current codes when specifying buildings.

Each new edition of the baseline energy codes brings increasingly stringent requirements for windows, particularly in terms of thermal performance. In the previous 15 years alone, ASHRAE 90.1 U-factors for windows reduced between 20 and 60 percent, depending on the climate zone.

The newest version of ASHRAE 90.1-2019 was approved in October 2019, and it continues its trend toward increased energy performance in glass and glazing systems. Among the updates include another 5–17 percent reduction in U-factor. In many cases, this creates roughly a “zone shift” between the 2016 and 2019 versions—what was required in Zone 7 will move to Zone 6, Zone 6 to Zone 5, etc. If products currently meet the requirements for one zone, it will not be too difficult to push that product into the next zone.

In general, the new code marks a push for improved framing, warm-edge spacers, argon gas fill, and fourth-surface low-e coatings. The new code also includes stronger daylighting requirements, including demand for more controls and toplighting.

There are two main code trends to watch: envelope backstops and verified performance requirements.

Envelope backstops require a minimum level of envelope performance, no matter what else is done in the building. These backstops can limit how much of the HVAC, lighting, and hot water systems can be used as a trade-off against envelope and window area components. These new backstops are being enacted in New York City, Massachusetts, and Washington state, but they will not be part of ASHRAE 90.1-2019 or 2021 IECC.

Also on the horizon are thermal bridging requirements. Thermal bridging refers to the more thermally conductive—or thermally inefficient—sections or components of a system or wall. Identifying and addressing the thermal bridges in a system will improve whole-system performance. “In the New York City energy code, architects are going to have to make drawings that show all the thermal bridges with details that quantify transmissions,” says Dan Piselli, director of sustainability at FXCollaborative. “At first, there will be no requirement, just documentation. … In the next code cycle, they are going to have performance requirements.”

Calls for verified performance will require project teams to prove their building lives up to energy and thermal performance targets after occupancy. A big driver of this is outcome-based codes. However, some developers and building owners are also adding contract clauses to withhold a portion of the payment until verified performance goals have been met. “We have started to see performance-based contracts. A team gets a base fee, and then gets more or less than that based on building performance,” says LBL’s Selkowitz.

What, roughly, will be required for glazing products to meet the U-factor requirements out-lined in ASHRAE 90.1-2019?

The table below provides a general idea of the potential glazing solutions to meet U-factor requirements. Note, architects will also need solar control products to meet SHGC requirements. Also note, the general product suggestions address performance attributes for window walls and, secondarily, sliding operable windows. Awning, vent, and casement operable products will have more difficulty complying. In these cases, it will be necessary to add extra features, or use area-weighted averaging for the facade, which will balance out higher and lower U-factor products.

Product assembly descriptions are provided to offer a general idea of what high-performance systems might be required in the various zones. Actual U-factor and SHGC ratings will depend on the specific frame, spacer, and low-e product choices. Do not rely on this for actual compliance.

Source: Tom Culp, Code Consultant, National Glass Association, and Owner, Birch Point Consulting

Product assembly descriptions are provided to offer a general idea of what high-performance systems might be required in the various zones. Actual U-factor and SHGC ratings will depend on the specific frame, spacer, and low-e product choices. Do not rely on this for actual compliance.

Code Requirements for Fire Protection

While meeting energy codes can reduce unwanted heat transfer and help reduce carbon emissions and a building’s carbon footprint, it is vital that buildings also meet fire-protection codes to ensure occupant safety. Fire has posed a reasonable risk to building structures and people for centuries. In 1896, the National Fire Protection Association (NFPA) was founded after the Industrial Revolution to help protect buildings and occupants from fire danger. The NFPA is a global self-funded non-profit organization that aims to eliminate death, injury, and property damage caused by fires. To help reach this goal, the NFPA regularly publishes codes and standards to help minimize the risk of fire danger. These standards are widely accepted and have been adopted and implemented throughout the world.

As previously discussed, there are two distinct performance categories—fire resistant and fire protective—that dictate fire-rated building requirements. Fire-protective products block the flames and gases, while fire-resistant products also block the radiant heat they create. These days, the industry is seeing more and more requests for fire-resistant glazing, partly because the demand for larger spans of interior glass has increased. In the example of corridors that feature lots of glass, architects must provide safe egress in the event of a fire. This is not only dictated by clear paths to exit the building but also by reducing the ability for fire and flames to spread. Fire-resistant glazing can help.

To ensure occupant safety, annual Fire and Egress Door Assembly Inspections are on the rise. Many local jurisdictions require that fire-rated doors be inspected annually to ensure they are fully functional over their lifespan. “This not only makes it critical that any replacement fire-rated glass is fully certified, but it also drives fire-rated door manufacturers to glaze with lightweight [glass ceramic products] right in their factory to ensure that the whole door is in compliance,” says Rob Botman, general manager, Glassopolis.

Existing Standards, Certifications, and Test Methods for Intruder Protection

While the threat of intruders and active shooters has become an increasing concern in modern times, there are currently no mandatory building code requirements for security glazing in schools, churches, hospitals, or other public places. However, a growing number of school districts nationwide have voluntarily decided to meet security glazing standards to provide additional protection for their school buildings.

In response to the increased number of threats, ASTM International is working on an industry-wide test standard to address mitigating armed attacks on buildings, with a focus on schools. Currently, there are impact standards, forced-entry standards, and bullet- and blast-resistant standards. However, standards organizations have yet to develop a standard or test method specifically for active-shooter resistance in schools.

In the absence of an industry-wide test standard, several individual companies have developed their own test methods, and those in the industry are diligently working together to create specs that can address all the variables. Many industry leaders hope they can gain consensus and publish standards by 2020.

Additionally, the NGA’s Fabricating Committee formed a task group to update the NGA’s Glazing Information Bulletin on school security glazing. The task group will explore developing a test method or guidelines for manufacturers looking to supply security glazing or systems for schools.

While new standards are in development, there are currently existing standards that are recommended for school security applications. ASTM E2395 is the most applicable to modern-day needs. ASTM E2395: Standard Specification for Voluntary Security Performance of Window and Door Assemblies with Glazing Impact was updated in 2018. The specification addresses systems intended to “frustrate opportunistic entry by unskilled and semi-skilled intruders,” according to ASTM. In the test, 2-by-4 missiles are projected at the glazing assembly with an air cannon. Then the system is hit 10 times with a ball-peen hammer. Since bullet-resistant glass is expensive, this glazing assembly was designed to provide schools with another option to help deter the entry of an intruder.

There are three main categories of security products: bullet resistant, forced entry, and blast resistant. Security-rated glass products must undergo certification and testing from an outside test lab. Key standards and test methods include: Forced-entry standards (ASTM F1233, ASTM F1915, UL 972, ASTM E2395), bullet-resistance standards (UL 752, NIJ 0108.01, WMFL ballistics and forced-entry test procedure), blast-resistance standards (ASTM F1642, ASTM F2248, ISO 16933), and school security standards (NFPA 3000). All of these standards and tests are currently voluntary.

Conclusion

When specifying glass and glazing, it is important to take a systems approach and consider the framing as well as other parts of the system, including HVAC and occupant needs and expectations. Glass and glazing can also provide occupant safety from fire and intrusion as well as comfort through thermal protection and daylighting.

Jessica Jarrard is an independent writer and editor focusing on health, science, and technology. She contributes to continuing education courses and publications through Confluence Communications. www.confluencec.com