Tag Archives: Glazing

To Test or Not to Test…? A guide to field quality control

Photo © BigStockPhoto/Vichaya Kiatying-Angsulee

Photo © BigStockPhoto/Vichaya Kiatying-Angsulee

by Sean M. O’Brien, PE, LEED AP, and David Artigas, PE

When properly implemented, field and laboratory testing of buildings and their systems and components can yield a wealth of useful information about construction quality, watertightness, durability, longevity, and other critical performance criteria.

Test results can help designers better evaluate ‘as-built conditions,’ understand any problems with the installation, and develop solutions appropriate to the specific problems that prompted the testing. When improperly implemented, however, testing can yield misleading results, lead designers to incorrect conclusions, and cause unnecessary expenses related to remedial work that may not really be warranted by the in-situ conditions.

In some cases, specifying inappropriate standards or performance criteria can create confusion or incite debate between the design and construction teams, especially in the event of a perceived failure. This article reviews some of the common test methods and procedures used in contemporary construction, with a focus on how the purpose of, and results from, these tests are often misunderstood.

This site-built interior chamber creates differential pressure across a curtain wall system for a test under American Architectural Manufacturers Association (AAMA) 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems.

This site-built interior chamber creates differential pressure across a curtain wall system for a test under American Architectural Manufacturers Association (AAMA) 503, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems. Images courtesy Simpson Gumpertz & Heger

The spray rack above has been positioned on the window exterior for AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products.

The spray rack above has been positioned on the window exterior for AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products.

 

 

 

 

 

 

 

 

 

 

 

Most important (but least asked) question
With dozens of industry organizations publishing thousands of test standards for buildings and building systems, there is almost always a quick answer to the questions: “What do I test and how do I test it?” However, the more important question, and one about which designers and contractors are often less sure, is “Why do I test?”

The answer to this question will almost always dictate the best method to use, the timing of the test, the pass/fail criteria, and sometimes whether it should be performed at all. In the case of poorly specified tests, the wrong tests are often performed ‘because it was in the specifications’ or ‘because the contractor owes us testing.’ Especially with fast-track construction projects, debates over testing are often brushed aside in favor of doing whatever the specification demands, regardless of the value of that testing.

In the authors’ experience, requiring designers to explain the reasoning behind their specified test methods or procedures can be an extremely useful exercise, either during the design process or as part of pre-construction activities. In the case of a designer having correctly specified test methods, the discussion can provide valuable information to the rest of the project team, giving everyone involved a better understanding of the reasons behind the testing. For improperly specified tests, the conversation can help avoid unnecessary testing and the resulting time/expense, as well as identify the correct test methods to determine the desired information.

Flood testing of a membrane waterproofing system on a rooftop parking deck occurs the finished paving is installed.

Flood testing of a membrane waterproofing system on a rooftop parking deck occurs the finished paving is installed.

Dye is used to color water during a roof flood test; it can help link interior leaks to specific areas of the roof above.

Dye is used to color water during a roof flood test; it can help link interior leaks to specific areas of the roof above.

Windows, doors, and curtain walls
Some of the most commonly tested building components are fenestration products—windows, doors, and curtain walls. For new construction, testing is most often specified as a quality control measure to ensure the installed system(s) meet the specified performance requirements for air and water penetration resistance.

The most common requirements are for testing in accordance with various American Architectural Manufacturers Association (AAMA) standards, depending on the system being evaluated. This requires the designer or specifier to know what type of system is specified as well as the relevant performance requirements to establish the appropriate test method.

There are different standards for different components, and some contain multiple test methods or options. For example, AAMA 501.1, Standard Test Method for Water Penetration of Windows, Curtain Walls, and Doors Using Dynamic Pressure, includes a method to test curtain fenestration for water penetration under dynamic wind pressure that requires a large fan—essentially, an airplane engine/propeller—and calibrated spray racks. There is also AAMA 501.2, Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, which is much easier to perform as it uses a simple handheld nozzle to spray along gaskets and joints. In this case, specifying testing per AAMA 501 is insufficient—the specific test method from that standard needs to be called out, as the two options vary greatly in scope and complexity.

In previous versions of the AAMA 501 standard, a third option (501.3) was available to perform water leakage testing under static pressure differential (Figure 1). Despite this test being pulled from the standard and replaced by AAMA 503-02, Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems, references to the 501.3 method can still be found in specifications written today. This often results in confusion when the time comes to perform the tests.

AAMA 501.2 is intended as a field check for water leakage—a simple, economical method to verify the general quality of the curtain wall installation. For compliance with a specified level of air- and water-penetration resistance, AAMA 503 must be used. It is important to note 501.2 is solely intended for fixed glazing systems; the high nozzle pressure used would likely cause moderate to severe leakage on operable vents or window products due to the inherent limitations of seals and gaskets used in operable fenestration.

For testing window assemblies (both fixed and operable) for compliance with a specified air- and water-penetration, AAMA 502, Voluntary Specification for Field Testing of Newly Installed Fenestration Products, is typically specified. This involves building a chamber on the interior of the product to allow for negative interior air pressure and using a spray rack to wet the exterior of the window (Figure 2).

It is important to understand this test method has a specific definition of what constitutes a leak. For example, water on the sill members that does not pass the innermost projection of the window is not considered a leak, since it does not reach a point where it can damage interior finishes. This can come as a surprise to designers witnessing the test and seeing water on the sill, only to find out that by the standard’s strict definition, the window is considered to not have leaked. For this reason, some specifiers add their own language regarding the definition of leakage, but may have difficulty holding a manufacturer to this definition in the event of a dispute.

It is also important for designers to clearly specify the pass/fail criteria for windows. This information can be derived from the performance class (e.g. R, CW, or AW) and grade for the product being tested, but is often misinterpreted, leading to confusion during the test or attempts to hold installers/manufacturers to unrealistic or non-industry-standard performance criteria.

Another caveat of AAMA 502 (since the 2008 revision) as well as AAMA 503 is they only apply to newly installed fenestration products. The standards define ‘new’ as products installed before issuance of the certificate of occupancy for the building or products that have been installed for less than six months.

This recent development is often a source of debate, as this means a window installed for six months and one day, even in an unoccupied/incomplete building, is no longer subject to AAMA 502 and therefore cannot be tested for compliance with the manufacturer’s stated performance criteria. In simpler terms, the manufacturer of the window is only held to its stated performance criteria for six months. For older products, AAMA 511, Voluntary Guideline for Forensic Water Penetration Testing of Fenestration Products, contains diagnostic procedures for identifying known leaks, but is not specifically intended to evaluate in-situ performance of non-leaking windows.

When specifying testing, it is important to make the distinction between test specifications, standard test methods, and testing guides. Each of these types of documents is used for a different, but often similar, purpose. Standard test methods, such as ASTM E1105, Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference, contains specific information on how to physically test these various components, what equipment to use, and related information.

Test specifications, such as AAMA 502, provide procedural information on the testing, the relevance/applicability of the testing, and related administrative information, and typically reference standard test methods (e.g. ASTM E1105) for the physical test procedures.

Finally, testing guides, such as ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls, are usually more general in nature and cover a wide range of components and procedures rather than focus on one specific area of the building enclosure. Similar to test specifications, these guides include procedural/administrative requirements and reference standard test methods for the actual testing procedures. Due to their non-specific nature, including ‘compliance’ with a testing guide such as ASTM E2128 as a specification requirement is likely to result in confusion, as it can be interpreted in many ways for many different components. A testing specification and pass/fail criteria must be clearly identified in the contract documents.

This depicts laboratory testing of brick masonry for compressive strength.

This depicts laboratory testing of brick masonry for compressive strength.

Water leakage through brick veneer/cavity wall can be seen from the interior through openings in the backup wall. The veneer does not provide actual waterproofing for this assembly due to presence of drainage plane and weather-resistant barriers.

Water leakage through brick veneer/cavity wall can be seen from the interior through openings in the backup wall. The veneer does not provide actual waterproofing for this assembly due to presence of drainage plane and weather-resistant barriers.

Roofing assemblies
Leakage from roofing systems, especially in the case of low-slope assemblies, can result in significant interior damage when left unchecked. There are many different methods for testing roofs, but not all are compatible with all assembly types. Understanding which methods can be used for which systems is key to specifying the appropriate test, whether as part of a specification for quality control in new installations or as part of remedial/troubleshooting efforts.

In this article, the authors focus on large-scale testing of roof areas, as opposed to smaller-scale testing of specific detail conditions (which is most often done using spray racks/nozzles or localized flood testing). As discussed, the roof’s configuration, as well as the specific membrane type, must be considered when specifying a test method.

The most obvious method of testing a roof—flooding it with water—can be effective in some cases, but extremely damaging in others. Flood-testing is best-suited to inverted roof membrane assemblies (IRMAs) where the membrane is installed directly over the structural deck, with insulation and ballast or other overburden above. In those cases, the testing is performed once the membrane and flashings are complete but prior to the installation of any overburden (Figure 3).

For this test, which is standardized in ASTM D5957, Standard Guide for Flood Testing Horizontal Waterproofing Installations, water is ponded over the system for a period of 24 to 72 hours, during which time the interior is reviewed for leaks. The depth of water must be reviewed to ensure the structural capacity of the roof is not exceeded, as every inch of water adds approximately 0.24 kPa (5 psf) of load. This can be challenging on large or complex roofs, where the deck slope may require compartmentalizing the test into smaller areas. Any leaks resulting from this test are likely to produce only localized damage which gets repaired along with the leaking component(s).

This test procedure is not appropriate for traditional ‘membrane-over-insulation’ roof systems, since leakage through the membrane may wet (and necessitate the replacement of) large areas of roof insulation. Especially in the case of a concrete roof deck, leakage through the membrane could go unnoticed or travel far from the original location as the deck retains the water, allowing large areas of insulation to become damaged and making it difficult to determine the leak’s source. These risks can be reduced by flooding only small areas at a time (limiting the amount of water that could enter the roof), in which case the water can be dyed to provide confirmation of leak sources if multiple areas are flooded in sequence (Figure 4).

There are several test methods available for traditional insulated roofing systems that do not carry the same risk of large-scale damage. These methods typically rely on specialized equipment to detect wet insulation below the membrane. Infrared (IR) thermography uses an infrared camera that visualizes temperature differences on surfaces by measuring and processing emitted radiation.

For an insulated roof, wet insulation will tend to retain more heat and cool slower than dry insulation. Since moisture from roof leaks is often trapped in the system for an extended period, scanning of a roof with suspected or known leaks shortly after the sun has set can help identify areas of wet insulation.

The IR camera measures the surface temperature of the membrane, so this method cannot be used on ballasted roofs since the ballast (e.g. gravel) will cool off uniformly and mask any small temperature differences on the membrane below. Similarly, testing on a windy day may yield misleading results as airflow over the membrane surface may even out temperature differences or cause the wet areas to cool off to the same temperature as the surroundings before the scan is made.

IR scanning of a roof is relatively efficient since large roof areas can be surveyed relatively quickly (some companies even offer aerial surveys, which can be economical for very large, open roof areas). A second method, often referred to as electrical capacitance/impedance (EC) testing, uses handheld or rolling (push-cart) equipment that sends electrical pulses into the roof system and measures the insulation’s ability to retain electrical charge. Wet areas will tend to hold a charge for less time than dry, allowing for relative comparison between areas. Similar to infrared, this method requires an exposed roof membrane since the scanner needs to be in close proximity to the insulation to be effective. For this method to be effective, the roof membrane needs to be non-conductive, making it ineffective on most ethylene propylene diene monomer (EPDM) assemblies or on membranes with metallized reflective coatings. For both of these methods, secondary verification (i.e. roof probes) of suspected wet materials should always be specified to confirm the efficacy of the test for the specific application.

A more recently developed test method uses specialized equipment to pinpoint specific defects in the membrane. In this method, a potential difference is created between the wetted roof surface and the grounded roof deck. Any breaches in the membrane create, in effect, a short circuit in the system which can be detected using specialized equipment.

This method can be used on both traditional and IRMA systems, but—similar to EC testing—the roof membrane must be nonconductive for the method to work. For new construction, especially on traditional roof systems, a grounding screen can be added below the membrane or cover board to provide more positive leak detection and become part of a permanently installed leak detection system. This type of system can be especially beneficial for vegetated roofing assemblies where the often significant amount of overburden can make locating leakage sites extremely difficult.

This infrared image shows air leakage around a window perimeter during a whole-building test.

This infrared image shows air leakage around a window perimeter during a whole-building test.

Brick masonry and exterior walls
Brick masonry has been a common building material in the United States since the colonial period, and mass masonry walls continued to be built through the first half of the 20th century. While the basic process of brick manufacturing has not changed much, modern technology allows the creation of brick typically much stronger and has greater uniformity of properties than historic brick. Historic lime mortars typically are softer and more permeable than modern cement mortars, which allows them to absorb greater stress within the wall from expansion and contraction or enables the wall greater capacity to ‘breathe.’

Concerns with historic masonry fall under two, often related, headings: the masonry’s structural capacity and durability. While it certainly is true modern masonry manufactured and constructed to meet modern standards should result in durable construction, it is not always necessary to hold historic masonry to these same modern standards, as the historic materials often have more than the necessary capacity to provide a long service life with good performance. Also, certain properties being lesser than modern standards may prove beneficial to performance.

The International Building Code (IBC) now has requirements for masonry properties such as compressive strength and performance in shear, though that was not always the case. Current codes are written for current construction, and do not always include previsions for how historic construction ‘works’ structurally. The International Existing Building Code (IEBC) includes provisions that allow historic buildings to remain, or repairs to occur, using original or like materials, but the structural engineer and code officials must still evaluate the structure’s capacity to withstand its loads and remain safe.

Structural engineers can use both non-destructive and destructive methods to determine masonry’s strength and ability to withstand stresses (Figure 5). It is important to specify testing appropriate to both the structure being evaluated and the goal of the evaluation. While a historic mass masonry wall may not meet the letter of the current code requirements, it may have capacity that exceeds its in-service loads with an acceptable factor of safety comparable to the code. That said, one concern with mass unreinforced masonry is it typically does not perform well during seismic events. In areas of higher seismic activity, greater care must be exercised in its evaluation.

Current requirements for energy efficiency mandate the building enclosure to have a specified resistance to heat transfer. While mass masonry walls typically have a lower R-value than modern insulated wall assemblies, they have an advantage—their bulk provides thermal mass unmatched by newer assemblies comprising several thinner layers of different materials sandwiched together. This thermal mass allows the wall to absorb and dissipate heat more slowly than modern walls, slowing the interior of the building’s reaction to changes in the exterior temperature and reducing the need for supplemental heating or cooling.

Changes to the thermal properties of a mass masonry wall, such as adding insulation to the interior, or significantly increasing the interior moisture load, may affect brick performance. Uninsulated historic masonry typically allows moisture to move through the wall (i.e. ‘breathe’) while remaining above the dewpoint, since the interior heat warms the wall.

The addition of interior insulation will reduce the wall’s temperature during the colder months. Water absorbed by the brick’s exterior wythe may go through freeze-thaw cycling as a result of the wall now being colder, and interior moisture that migrates through the wall assembly may condense on the inboard side of the masonry wall, because this side of the wall now is on the ‘cold side’ of the insulation.

Historic masonry may have two advantages that will reduce the likelihood of these two events occurring.

1. Historic brick typically is more porous than modern brick. This greater porosity may allow the brick to ‘drain’ rainwater more quickly than modern brick, and the larger pores may allow the absorbed water more room to expand without causing damage.
2. Historic lime mortars are more absorptive and permeable than modern mortars, and these properties may allow the mortar to wick water rather than having it remain on the wall.

However, it must be stressed the reaction of mass masonry to the installation of interior insulation is still a topic of study among engineers and preservationists. Further, there are currently no established guidelines for insulating walls, only various opinions on the matter.

Many designers of renovation projects may equate strength with durability and specify masonry testing with this thought in mind. Great care must be exercised when considering insulating mass masonry walls, and testing of the masonry’s porosity, absorption, permeability, expansion, and relative strength (both of brick and of mortar) should be performed. Additionally, laboratory testing and evaluation to determine the relative durability of the brick, as well as its resistance to freeze-thaw damage, are a crucial part of this kind of study.

It is also critical to evaluate test results in light of numerous factors, such as the type of building/occupancy, building use, and general quality of the surrounding construction. If a sampling of brick test as SW grade (suitable for severe weathering per ASTM C216, Standard Specification for Facing Brick [Solid Masonry Units Made from Clay or Shale]) that does not necessarily mean the wall assembly in question has the level of durability required for the specific application. SW brick on a large, clear wall area will likely provide suitable performance, but the same brick installed in a shaded location (i.e. minimal drying) below a window that experiences leakage (i.e. excessive wetting) may undergo premature degradation regardless of the brick grading.

The most important question to ask when evaluating a historic masonry building is: “How has it performed thus far?” If the building shows no obvious signs of distress after several decades or even centuries of use, its testing and evaluation must begin from a position of “How does it work?” as opposed to one of “Does it meet the code requirements for modern construction?”

This understanding will include site observations and possibly onsite or laboratory testing, and research into historic construction methods and materials. Ultimately, this approach to evaluating historic masonry may lead to a more efficient and lower cost project that also can maintain the building’s character. Regardless of testing, designers who take this approach much understand when the use of the building or other characteristics of the enclosure are changed as part of renovations, the prior performance of the building may not be a suitable predictor of long-term durability.

From a water penetration standpoint, there are many different test methods available for masonry walls, but not all provide useful information. For example, ASTM C1601, Standard Test Method for Field Determination of Water Penetration of Masonry Wall Surfaces, determines water penetration at the surface of a masonry wall, but does not provide any information on how much water actually leaks to the interior (as opposed to water that is absorbed and stored by the masonry). Similarly, RILEM tubes can be used to provide relatively quick evaluations of the water absorption rate of a masonry wall.1

ASTM E514, Standard Test Method for Water Penetration and Leakage Through Masonry, provides for measurement of the actual amount of water penetrating the full thickness of the masonry, but this is a lab test not applicable to field conditions (although it is often specified—incorrectly—by designers evaluating existing masonry buildings). Field surface absorption tests may have limited use in qualitatively evaluating the change in absorption that results from installing a penetrating sealer, but are typically of little to no use in evaluating water leakage.

Neither of these tests will be of practical value for masonry cavity wall construction, where any water penetrating the exterior façade is collected in a drainage cavity and wept out of the system (Figure 6). Water leakage through a masonry cavity wall is more likely the result of a breach in the water-resistive barrier (WRB) behind the masonry, since masonry veneer systems are expected to allow water into the drainage cavity.

The authors have generally found the general guidelines from ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls—as opposed to one specific standard test method—are helpful in establishing the right combination of testing and inspection to diagnose water leakage through masonry walls.

Air barrier systems
As far as building testing goes, the testing of air barrier systems is a relatively recent development.2 Just as with window and curtain wall testing, there are multiple test standards and guides for testing air barrier systems in both the lab and the field. One of the first points of confusion is the definition of an air barrier—a system of interconnected components including walls, windows, curtain walls, and roofs that act together to prevent uncontrolled airflow into and out of the building. While air barrier testing is often thought of as testing a wall air barrier membrane (one component of the system), it can encompass everything from single materials to the entire building enclosure.

Some of the most commonly tested building components are fenestration products like windows and curtain walls. For new construction, testing is most often specifi ed as a quality control measure to ensure the installed systems meet the specifi ed requirements for air and water penetration resistance. Photo © BigStockPhoto/Graça Victoria

Some of the most commonly tested building components are fenestration products like windows and curtain walls. For new construction, testing is most often specified as a quality control measure to ensure the installed systems meet the specified requirements for air and water penetration resistance. Photo © BigStockPhoto/Graça Victoria

Testing of actual materials, such as sheet- and fluid-applied membranes, is performed in the laboratory due to the very small quantity of air leakage being measured and the high degree of accuracy required in the measurement. Air barrier products are required by most codes to allow no more than 0.02 L/s.m2 @ 75 Pa (0.004 cfm/sf at a pressure differential of 0.3 in. of water). In reality, most sheet membranes (such as self-adhered rubberized asphalt products) exceed this criteria by an order of magnitude or greater—much too low to be reliably measured in the field.

Air barrier assemblies—essentially, air barrier materials in an as-built condition that includes laps, seams, and penetrations—can be tested in either the lab or the field. Laboratory testing per ASTM E2357, Standard Test Method for Determining Air Leakage of Air Barrier Assemblies, provides an air leakage rate for a pre-defined arrangement of air barrier products, penetrations, and a window opening (but not the window itself—an oft-overlooked element of the air barrier system).

While primarily a laboratory test used by air barrier manufacturers to demonstrate their products’ performance and code compliance, the method can also be applied to field-installed mockups. However, applying this test in the field is not as simple as installing a chamber on the interior and testing the exterior. Air leakage through the perimeter of a sample area (e.g. through a concrete block or stud wall perpendicular to the interior-exterior direction) is often impossible to isolate, and due to the relatively low leakage rates being measured, even a small amount of extraneous leakage can create a false negative test result. Using this general chamber testing approach on a qualitative basis is simpler and often more effective, since telling a contractor that the test result was 0.25 L/s.m2 (0.05 cfm/sf)—in other words, a failure—does not provide the same level of usefulness as telling them there were leaks at one membrane seam and two brick ties that need to be repaired.

Specifications for field-installed air barrier assemblies often include testing of the window as part of the assembly. While this makes sense from a practical standpoint (i.e. the connection to the actual window system is a critical transition in the air barrier), there are limitations to this test. From a practical standpoint, mockup testing of air barrier assemblies typically happens at the beginning of a project, often long before the windows are delivered to the site (or in some cases, before specific window products are even selected). Testing of the assembly with a ‘dummy window’ in place is possible, but results can be misleading since the actual connection is unlikely to be the same as what is intended for the project windows.

In cases where the dummy window is put in temporarily with sealants and sprayed-applied foam insulation, the actual leakage rate may be much lower than what will occur when the project windows are installed, giving a false positive result for the test. In the case of the project windows being available at the time of testing, the specification of pass/fail criteria for the air barrier assembly test becomes more important. The performance criteria for air barrier assemblies are based on a window perimeter being included, but not the window itself. Since most windows will experience significantly higher leakage (on an area basis) than air barrier materials and assemblies, leakage through the window may far exceed the air barrier assembly leakage criteria, even if the assembly itself, minus the window, would pass on its own. For this reason, it is important to clearly specify how and if the window is to be included in the test, and, if so, some increase in allowable air leakage needs to be included to avoid requiring a result which is not attainable in the field.

The third type of air barrier testing is whole-building testing, using blower door or similar equipment and ASTM E779, Standard Test Method for Determining Air Leakage Rate by Fan Pressurization, procedures to measure overall air leakage through the entire building—including all walls, roofs, and windows. Different codes and standards require different overall leakage rates, but 0.02 L/s.m2 @ 75 Pa (0.4 cfm/sf at 0.3 in. of water) is typical for most building and energy codes.

While this test provides a single number to describe air leakage that can be easily compared to other buildings, it has many limitations that must be considered before requiring a certain level of whole-building performance. The first major issue is at the time when the air barrier is substantially complete to the point where testing can be performed, it is also likely to be concealed by cladding and other materials that can make the detection (using IR thermography or tracer smoke) and repair difficult or impossible.

Second, the testing itself can be difficult to perform, especially on large/more complex buildings, due to the need for multiple fan systems that must all be linked together for measurement or adjustment. In tall buildings, internal fans may be needed to equalize pressure differentials over the height of the building. While most testing firms can easily come to a site and perform standard window or curtain wall tests, large-scale testing of whole buildings requires specialized equipment and a fair degree of experience and expertise to successfully execute.

Lastly, there is some debate over what is achievable in terms of air leakage through whole buildings. A designer can certainly specify the overall leakage rate needs to be 0.5 L/s.m2 (0.1 cfm/sf), but achieving that level of airtightness requires an exceptionally well-designed air barrier, as well as carefully planned execution of the construction.

This is a common mistake with all types of air barrier testing—specifying a high level of airtightness without providing the corresponding design detailing is a futile effort. As mentioned, once the building is physically ready to be tested, it is often far too late to practically implement repairs, which brings up the difficult question of “What do we do now that we failed the test?” While the industry is still working on answering that question, specifiers can help avoid problems by specifying reasonable levels of airtightness appropriate for the building design.

As with the other previously described tests, visualization techniques such as infrared thermography and tracer smoke can be used to take advantage of the pressure differential created during a whole building test and qualitatively identify air leakage sites (Figure 7).

Conclusion
While the wide variety of available testing standards means there is almost always a standard for the designer’s specific need, finding the right standard can be difficult when one does not have a firm understanding of the actual goals. Designers and specifiers should first evaluate the question of ‘why’ when it comes to testing, as the answer will typically guide them to the correct test method to follow.

Specifying both the appropriate testing method and the appropriate pass/fail criteria are necessary to provide meaningful test results and avoid the time and expense of unnecessary testing or inappropriate testing which leads to ambiguous results. A little more time spent researching test methods during the design phase and specifying appropriate methods and performance criteria can go a long way toward reducing confusion and disputes during the construction process in the field.

Notes
1 For more on RILEM tubes, see The Construction Specifier articles, “Testing the Test: Water Absorption with RILEM Tubes,” by Adrian Gerard Saldanha and Doris E. Eichburg, and “Durable Waterproofing for Concrete Masonry Walls: Redundancy Required,” by Robert M. Chamra and Beth Anne Feero in the August 2013 and July 2014 issues. (back to top)
2 For more on air barriers, see the article “Wind Load and Air Barrier Performance Levels,” by Maria Spinu, Ben Meyer, and Andrew Miles, in the July 2014 issue. (back to top)

Sean M. O’Brien, PE, LEED AP, is an associate principal at the national engineering firm Simpson Gumpertz & Heger (SGH), specializing in building science and building enclosure design and analysis. He is involved in both investigation/forensic and new design projects. O’Brien is a member of the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE), co-chair of the New York City Building Enclosure Council (BEC-NY), and a frequent speaker and author on topics ranging from building enclosure design to energy efficiency. He can be reached at smobrien@sgh.com.

David Artigas, PE, is senior staff I–building technology at SGH, specializing in building enclosure design and investigation, building science, and historic preservation. He can be reached at djartigas@sgh.com.

Meeting Efficiency Codes without Compromising Design: Technology that Meets Specifications

A full-scale mockup incorporating architectural insulation modules.  [CREDIT] Photo courtesy Dow Corning Corporation

A full-scale mockup incorporating architectural insulation modules. Photo courtesy Dow Corning Corporation

by Stanley Yee, LEED AP

To help overcome concerns about adoption of new technology, a full-scale mockup of a high thermally performing curtain wall incorporating architectural insulation modules was recently successfully tested by an independent third-party. Testing was conducted in accordance with American Architectural Manufacturers Association (AAMA) 501, Methods of Test for Exterior Walls, ensuring acceptable performance for air and water penetration resistance, structural capacity, and vertical and seismic movement requirements.

To read the full article, click here.

Meeting Efficiency Codes without Compromising Design

Photo courtesy of University of Birmingham

Photo courtesy of University of Birmingham

by Stanley Yee, LEED AP

Creating an effectively insulated envelope is necessary for buildings to meet the latest demands of ever-tightening energy codes. Innovative use of high-performance insulation technologies enables architects to achieve improved insulation performance using common building techniques without sacrificing aesthetics.

Thin-profile, high-performance insulation materials that seamlessly integrate into conventional glazing systems now give designers flexibility to better manage and balance thermal performance and façade aesthetics. Materials such as vacuum insulation panels (VIPs), architectural insulation modules (AIMs), and aerogel building insulation blanket materials are becoming more prevalent.

For many years, inexpensive energy made it possible to design buildings without regard for energy performance. The global movement toward sustainability has led to tightening regulations often restricting design freedom.

Local, national, and global organizations continue to develop codes that mandate increased thermal performance in insulation and, in turn, reductions in energy consumption. Construction in the United States can be subject not only to prevailing building codes, but also standards such as American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings, with increasing pressure to comply with voluntary standards and certifications such as the United States Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) v4. Other drivers include:

  • 2012 International Energy Conservation Code (IECC);
  • Living Building Challenge;
  • growing demand for net-zero buildings; and
  • American Institute of Architects’ (AIA’s) 2030 Challenge.

From a design standpoint, simply increasing the amount of conventional insulation used in a building is neither practical nor aesthetically pleasing. New insulation technologies provide the performance advantages necessary to achieve effective building envelope insulation without sacrificing design aesthetics.

Integrated use of high-performance insulation in the curtain wall spandrel, in Calgary, Alberta, enables high window-to-wall-ratio designs that meet energy codes. [CREDIT] Photo courtesy BIG

Integrated use of high-performance insulation in the curtain wall spandrel, in Calgary, Alberta, enables high window-to-wall-ratio designs that meet energy codes. Photo courtesy BIG

Thermal performance of commercial insulation materials. [CREDIT] Images courtesy Dow Corning Corporation

Thermal performance of commercial insulation materials. Images courtesy Dow Corning Corporation

 

 

Balancing design trends with energy performance
Cognizant of the need for energy performance, architects are put in a challenging position. Designers are pressured by current building trends to include as much glazing and vision area as possible for optimal aesthetic value, striving to create iconic buildings of aluminum and steel with floor-to-ceiling glass. However, this rise in the use of glass means increasing energy performance can be challenging.

Unfortunately, extensive use of vision glazing is generally lower in thermal performance. To achieve an overall desired level of exterior wall performance, architects and designers must depend on the non-vision spandrel sections.

Used on the façades of commercial buildings, these opaque spandrel sections—typically composed of metal, stone, or glass panels—are used to conceal the floor lines. The spandrels are often designed to visually blend so closely with the vision glass they are not even perceptible, creating the effect of a uniform, all-glass building (Figure 1). They also are manufactured in various colors and designs, adding additional visual interest to the curtain wall’s appearance.

More importantly, the spandrels can be highly insulated to contribute to the façade’s overall thermal performance. Leveraging technical design opportunities in the spandrel sections allows designers to maximize the vision area and still meet prescribed thermal performance requirements of energy conservation codes, such as ASHRAE 90.1 and IECC.

Mineral wool requires eight to 10 times the thickness to provide the equivalent insulation value of a vacuum insulation panel (VIP).

Mineral wool requires eight to 10 times the thickness to provide the equivalent insulation value of a vacuum insulation panel (VIP).

Traditionally, spandrel areas need to be supplemented with an additional layer of thick mineral wool or similar conventional insulation to achieve the necessary thermal value. However, in higher climate zones, such as Climate Zones 4 and 5, this approach may require additional space within the curtain wall to accommodate the required thickness to achieve thermal performance targets. Thin-profile high-performance insulation technologies can solve these challenges.

Beyond the building’s outward aesthetics, architects are also facing the challenge of mitigating uncontrolled thermal losses due to thermal bridging across the building envelope. These heat losses typically occur at transitional conditions in building envelopes, such as:

  • exposed slab edges;
  • where glazing systems meet cavity wall components;
  • where below-grade and above-grade systems meet; and
  • where parapets meet roofs.

Building codes and regulations now require mitigation of thermal bridging conditions. They can make it especially challenging for architects to retrofit existing designs with insulation solutions meeting both performance requirements and available space limitations.

New applications for high-performance insulation technologies
Architects and designers have additional flexibility to respond to insulation performance challenges with high-performance insulation technologies, such as vacuum insulation panels. VIPs can be integrated into architectural insulation modules to enable whole-wall envelope thermal performance improvements; aerogel building insulation blankets can also be included to help address detail-specific thermal bridging issues. These materials not only demonstrate a step-change in thermal performance compared to traditional insulation materials, but also enable designs using current construction techniques to meet demands of the next generation of thermal requirements.

Figure 2 shows the thermal resistance (i.e. RSI, R-value) which is typically expressed as R-value per inch, of various insulation products, including materials typically found on a job site such as expanded polystyrene (EPS), mineral wool, and polyisocyanurate (polyiso). As demonstrated by Figure 2, the change to higher-performing materials is significant, with silica-fume-based vacuum insulation panels as high as RSI 5.63 to RSI 6.16 per 25 mm (R-32 to R-35 per inch) and the aerogel building insulation blanket at RSI 1.73 per 25 mm (R-9.8 per inch).

Composition of vacuum insulation panel.

Composition of vacuum insulation panel.

Thin-profile vacuum insulation panels
Vacuum insulation panel technology provides designers with new options. Offering insulation in a slender profile, a VIP’s thermal performance gives it the equivalency of eight to 10 times the thickness of mineral wool insulation typically used on a construction site (Figure 3).1

Forms of vacuum insulation were invented more than a century ago, and interest has grown over the past several decades in applications where constrained space and weight benefits justify the higher cost, such as commercial applications, as well as in ‘cold-chain’ applications, such as insulated shipping and transport containers. Now, the technology is finding its place in commercial façade insulation applications.

VIP construction (Figure 4) is based on a pressed fumed silica core, which is formed and heated to drive out the moisture. It is then inserted into a handling bag (i.e. core bag) and then into a multilayer, aluminized bag. As that bag is put under full vacuum, its edges are heat-sealed. When the vacuum is released, a full vacuum is contained within the bag. With the vacuum, all the atmospheric gases around the fumed silica are removed, therefore eliminating convective heat transfer from the gases within. With the full vacuum, the unit achieves the initial RSI 5.6 to RSI 6.2 per 25 mm (R-32 to R-35 per inch) center-of-panel (COP) performance. Without the vacuum, the material provides about RSI 1.4 per 25 mm (R-8 per inch), which is approximately twice as good as typical foam insulation—so even if the material loses its vacuum, it continues to provide good insulation performance.2

VIP offers many advantages. It has low nominal thermal conductivity—approximately 4 mW/mK at COP. The metalized bag around the panel is inherently moisture-resistant. The fumed silica core is an ash created by burning a silane. Essentially, the material has already been burned, providing a high degree of fire resistance. The VIP’s thin profile can also allow it to solve various problems; for example, increasing thermal performance requirements not being met by conventional means, or maintaining thermal performance requirements while allowing for increased vision area.

VIP is a pre-engineered product and must be customized by the manufacturer or packaged as part of a system; it cannot be cut to size onsite, as cutting or puncturing the material would cause a vacuum loss and resulting loss of thermal performance.

Cutaway view of architectural insulation modules incorporating VIP technology.

Cutaway view of architectural insulation modules incorporating VIP technology.

Architectural insulation modules are available in various finishes to meet aesthetic requirements.

Architectural insulation modules are available in various finishes to meet aesthetic requirements.

 

AIMs–integrated curtain wall application of VIP
The façades of modern glass curtain walls typify an ideal application for vacuum insulation panel technology. Curtain walls create the iconic artwork and unique character of a building. The ability to maintain a slim façade with a high thermal performance gives the architect the design freedom to maximize the wall’s vision area and/or thermal performance while still meeting local building codes.

For curtain wall applications, VIP technology is provided in an integrated façade module known as an architectural insulation module, which combines a VIP with a protective architectural finish (Figure 5). The module has a back pane of a rigid structural panel material, joined with a warm edge spacer (as used in the insulating glass industry) around the perimeter. VIP is inserted into the space—which typically is the air space in an insulating glass unit—and covered with a finished panel on the front. Modules are available in various architectural options, including opaque, metal, and glass with ceramic frit or ceramic frit patterns (Figure 6).

Performance of architectural insulation modules of various thicknesses.

Performance of architectural insulation modules of various thicknesses.

Modeling and guarded hot-box testing demonstrates the performance characteristics of architectural insulation modules technology (Figure 7). A 25-mm (1-in.) thick unit modeled with a two-dimensional finite element thermal analysis software package, resulting in an effective RSI 1.90 (R-10.84) and a COP value of RSI 3.84 (R-21.8).

A 50-mm (2-in.) thick unit is tested with ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus. Figure 7 shows actual test results of a 50-mm thick structural panel, which includes a 6-mm (1/4-in.) piece of glass on each side and a 38-mm (1.5 in.) VIP in the interspace, sized at 1.5 x 1.5 m (5 x 5 ft), indicating an effective RSI of 3.4 (R-19.05). The effective R-value is lower due to factors including heat losses around the insulating glass spacer assembly.

In addition to demonstrating superior thermal performance, the AIM is designed to meet the physical demands of commercial façade applications, withstanding typical windloads and meeting structural requirements. Constructed to standard or custom spandrel size specifications, the modules require no special installation techniques, eliminating need for specialized installer training.

Effect of VIP on U-value and window-to-wall ratio performance.

Effect of VIP on U-value and window-to-wall ratio performance.

Whole-wall insulation performance
Designing a slim façade with a higher percentage of vision requires the lowest possible U-values for spandrel areas to augment thermal performance characteristics. VIP-integrated façade modules enable additional vision area while still complying with thermal performance requirements, improving the curtain wall’s overall whole-wall performance.

When this technology is applied to a building design, it increases thermal performance by maintaining the same window-to-wall ratio, but its replacing of traditional insulation with architectural insulation modules, increases overall curtain wall thermal performance (Figure 8, Arrow 1).

Further, it increases design freedom as architects gain ability to potentially increase window-to-wall target ratios substantially, without compromising on the insulation value of the curtain wall configuration (Figure 8, Arrow 2X).

Blanket insulation
Like the vacuum insulation technology, aerogel is not a new concept, but it has been optimized for the next generation of building challenges. Invented in the 1930s, the material is composed of 95 to 99 percent air, making it one of the lightest materials. Its nanoporous structure minimizes thermal transport, giving it low thermal conductivity. It has been used in various applications, especially aerospace, but with tightening environmental requirements and increasingly complex building designs, aerogel insulation has now found a new niche providing thermal protection in space-restricted areas.

An aerogel building insulation blanket is made from synthetically produced amorphous silica gel. It features a small particle size, with the diameter of the spaces between aerogel particles similar to the fumed silica in the vacuum insulation panels. Manufacturing this material in a blanket form (Figure 9) creates a usable, flexible, construction-friendly material that can be cut-to-size onsite and applied to reduce the thermal bridging at specific locations in a building envelope assembly. Aerogel building insulation blankets are highly resistant to flame, with an ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials, Class A fire rating (flame spread index 5, smoke developed index 10).

Flexible, highly insulating aerogel building insulation blanket.

Flexible, highly insulating aerogel building insulation blanket.

Linear transmittance reductions with aerogel building insulation blankets.

Linear transmittance reductions with aerogel building insulation blankets.

 

Minimizing thermal bridging
Updating architectural details to address thermal bridging concerns has become more common due to increasingly explicit and stringent building codes. The availability of a thin, flexible insulation material reduces the need to make trade-offs in design to meet codes and regulations, and it eliminates bulky or messy insulation from those tight areas of building designs.

Based on ASHRAE Research Project (RP) 1365, Thermal Performance of Building Envelope Details for Mid- and High-rise Buildings, three common construction details were modeled to demonstrate the effect of using aerogel building insulation blankets to minimize thermal bridging. These models are:

  • curtain wall-at-grade detail with the aerogel building insulation blanket applied from the neck of the curtain wall to the below-grade rigid insulation, resulting in a reduction in linear thermal transmittance approaching 25 percent;
  • curtain wall jamb at the exterior and interior insulated steel stud assembly with the aerogel building insulation blanket applied around the adjacent steel stud and at the wall-to-curtain wall transition, resulting in a reduction in linear thermal transmittance approaching 70 percent; and
  • rehabilitated window-wall system with the aerogel building insulation blanket at the slab edge and around vertical and horizontal glazing mullions, resulting in a reduction in linear thermal transmittance approaching 53 percent.

Lineal transmittance values can readily be incorporated into thermal models. This eliminates the guesswork and improves the predictability of the heat loss due to thermal bridging at those locations. (See Figure 10.)

Additionally, two whole-building energy models were created to demonstrate the effect of using aerogel building insulation blanket with conventional and higher-performance assemblies to minimize thermal bridging:

  • for a building with the glazing system covering 100 percent of the façade area, addition of the an aerogel blanket, with conventional assemblies resulted in a 3.56 percent energy savings;3 and
  • for a façade with curtain wall glazing and a steel stud wall assembly, addition of the aerogel blanket and higher-performing assemblies resulted in a 6.78 percent energy savings.4 (See Figure 11)
Annual heating energy savings for Chicago climate.

Annual heating energy savings for Chicago climate.

Conclusion
Vacuum insulation panels, architectural insulation modules, and aerogel building insulation blankets have been introduced in a range of construction projects in the United States and Europe, with positive response.

In an age of increasingly dramatic building design, architects can take comfort in knowing design does not have to take a backseat to performance and energy efficiency issues in current designs can often be addressed with innovative application of high-performance insulation materials.

Notes
1 For more information, see ASHRAE Fundamentals Handbook 2009. (back to top)
2 Visit Vacuum Insulation: Panel Properties and Building Applications at www.ecbcs.org/docs/Annex_39_Report_Summary_Subtask-A-B.pdf. (back to top)

Stanley Yee, LEED AP, is a façade design and construction specialist for Dow Corning High Performance Building Solutions. He joined the company in 2012 with nearly 20 years of experience in the building enclosure industry, working with curtain wall contracting, façade consulting, and enclosure detailing specialists both nationally and internationally. Yee earned a bachelor of engineering degree from Concordia University (Montréal, Québec). An active member of several industry organizations, he is an elected officer of the Board of Directors for the Glass Association of North America (GANA), representing the Energy Division. He can be contacted via e-mail at stanley.yee@dowcorning.com.

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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).

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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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