Tag Archives: Glazing

Quality Control Issues with Fire-related Laminated Glazing

fireglass_Dwyer_141114_1096

Photo courtesy Technical Glass Products

by David E. Sacks, R.A., AIA, LEED AP, and Bradford S. Carpenter, PE, LEED AP
Historically, glazing has been used to provide light and ventilation in building walls as its primary function. In contemporary buildings, specialized glazing can provide numerous other functions, including fire-resistance.

The percentage of glazed surface area on buildings continues to increase. One of the reasons is the link between access to natural light and improved health, comfort, and productivity of occupants. This factor, along with the energy costs associated with internal lighting and the resulting cooling loads, have focused attention on the positive attributes of daylighting, in turn driving both policy and architectural aesthetic toward greater use of glass in the building enclosure.

This desire to maximize glazed surface area has been a major factor in the development and increased acceptance of fire-rated curtain-wall glazing systems. While the development of these products continues and manufacturers look to expand market share, the expectations of professionals and end users do not always reflect actual product performance (in terms of optical clarity and aesthetic factors like color).

Similarly, the newness of these products results in undeveloped standards and codes, not fully equipped to check or maintain quality control. Additionally, the infancy of product to the construction market also causes contractor unfamiliarity. Fire-rated curtain wall assemblies are inherently different from non-rated curtain wall assemblies with respect to physical characteristics and installation and handling requirements.

Background
Fire separation distances between adjacent buildings (and stepped portions of the same building) trigger specific code requirements regarding fire-resistance ratings and maximum area of exterior wall openings (Figure 1). Historically, fire-resistance-rated walls have been solid masonry, concrete, or similar non-combustible construction with limited fire-protected openings to fulfill fire-escape egress and light or vent requirements. These openings would be protected with fire-protective-rated window and/or door assemblies—typically, steel fenestration glazed with wired glass or individual units of glass block. The building code further restricts the height, width, and overall area of each glass panel in a fire-protective-rated opening.

fireglass_Fire Separation

Figure 1: International Building Code (IBC) Figure 705.8.6 (Vertical Fire Exposure of Adjacent Building) illustrates the requirement for opening protectives due to the fire separation distance of two adjacent buildings (less than [4.5 m] 15 ft from the building/structure to an imaginary line between the adjacent buildings). Image courtesy IBC 2012

In 2006, the revision to the International Building Code (IBC) included a new section, Section 706.2.1–Fire-resistance-rated Glazing, which was added to clarify the distinction between fire-resistance-rated glazing and fire-protection-rated glazing.

While both types of glazing limit the spread of flames during a fire, fire-resistance-rated glazing also provides a radiant barrier. As such, this glazing may be used to construct the fire barrier—in other words, it is the fire-resistance-rated wall, not just a protective opening in said wall. The 2012 IBC went a step further in clarifying the role of fire-resistance-rated glazing when it published Table 716.3, “Marking Fire-rated Glazing Assemblies.” This table states the “W” marking classifies an assembly as “meeting fire-resistance-rated wall assembly criteria.” The development of intumescent fire-rated glazing—which meets IBC 706.2.1—was a catalyst behind this change.

Intumescent
The term ‘intumescent’ characterizes a material that swells and chars when exposed to flame, forming an insulating fire-retardant barrier between the fire and the material. The development of intumescent materials—such as hydrated sodium silicate, graphite, and mono-ammonium phosphate (MAP)—has enabled glazing systems to make the leap from fire-protective to fire-resistant. As such, the creation of fire-resistive glazing assemblies has virtually erased the limitations on which building surfaces can or cannot be glazed. This has enabled architects to design with more transparent fenestration systems in an effort to achieve aesthetic goals or maximize daylight.

Manufacture and assembly
In order to create intumescent laminated glass, large sheets of annealed glass are set onto horizontal racks with a silicone bead along the perimeter to create a reservoir that is then filled with hydrated sodium silicate in either liquid or prill (i.e. bead) form. Each sheet is then low-baked (<37.7 C [<100 F]); once the intumescent material is set, the perimeter is trimmed off to remove the silicone bead. This process precludes the use of heat-treated glass as the base product in an intumescent laminated glass assembly.

fireglass_Intumescent Glass Illustration rev

Figure 2: This is a section diagram of intumescent laminated glass. Image courtesy The Schott Group

The individual intumescent laminated sheets are then configured according to the desired fire-rating requirements, and baked in an autoclave at a slightly higher temperature to create the final sandwich panel (Figure 2). When that panel is intended for a monolithic installation, an additional layer of glass with a polyvinyl butyral (PVB) lamination is added to one side (i.e. asymmetric) or both sides (i.e. symmetric) of the sandwich panel, depending on the intended use. The panels are then cut to size with a diamond-blade saw and the edges sealed with a special metallic perimeter tape to protect the intumescent interlayer during transportation, construction, and in service.

Material and system limitations
Since the intumescent lamina is not inherently stable, it needs to be protected to prevent deterioration through absorption of atmospheric moisture and general exposure to the atmosphere. Hydrated sodium silicate, which is frequently used as the lamina material, is particularly sensitive to high temperatures, ultraviolet (UV) radiation, and water—a significant challenge, particularly for applications as exterior fenestration glazing. As such, the PVB lamination at the exterior face, the perimeter edge tape, and the unit’s general storage/handling are critical to the sandwich panel’s performance and they hint at the intumescent material’s limitations.

Several intumescent glass manufacturers indicate products must be protected from temperatures at or above 50 C (122 F). This limitation applies to internal (i.e. radiators or halogen lights) and external sources of heat. Additionally, particular attention should be paid to where the external sheet of glass is made of highly absorptive glass (e.g. body-tinted). This temperature sensitivity will limit the applicable climates as well as specific exposures where this glazing may be installed.

Revised Image as requested

Figure 3: This is a sample of 120 intumescent laminated glass with protective metallic tape (arrow) along the perimeter of the glass. Photos courtesy David E. Sacks

The special aluminum tape along the edges provides protection against moisture and general exposure to the atmosphere (Figure 3). Should the tape lose adhesion and become de-bonded before installation in the fenestration system, it must be replaced or taped over prior to installation, and this may have an impact on the product warranty.

One manufacturer’s product warranty, for example, states: “The removal of edge tape from the laminated assembly voids the warranty.” For a full-frame system, where the edges of glass are concealed by the metal frame, the edge tape typically returns to each face of glass 6.35 to 9.5 mm (14 to 38 in.). However, in a butt-glazed configuration, the edge tape does not return to the face of the glass and is much more susceptible to damage during the handling and installation processes.

The application of PVB at the exterior face of all intumescent glazing units reduces UV degradation to the intumescent material, and it is critical for asymmetric units that the non-PVB protected face not be exposed to UV during transport, storage, or installation. Manufacturers provide their products with a stamp readable from the UV-opposed side as 
a guide to installation contractors.

Beyond just the glass orientation, the product’s installation procedure varies greatly from that of a typical curtain wall system. While a traditional curtain wall may use a pressure-glazed system with a pressure bar to seal the gaskets to the glass surface, intumescent laminated glass systems often require only a fraction of that pressure.

On reviewing the product documentation and installation manual of one fire-rated curtain wall system, one manufacturer specifically notes:

Edge pressure must be between 4–10 pounds per linear inch. This pressure is required on the (curtain wall system’s) mullion gaskets. It must be uniformly applied by the exterior-mounted pressure plate, through the glass to the mullion gaskets. Excessive edge clamping pressure will cause deformation and breakage.

The installation manual goes on to describe the pressure plate installation: “Tighten the screw until a maximum of 1.13 to 1.69 Nm (10 to 15 in. pounds) of rotational torque is achieved.” As a point of reference, one non-fire-rated curtain wall system manufacturer states in its literature to torque all pressure plate bolts to 5.65 Nm (50 in. pounds).

As implied by the reduced pressure, intumescent laminated glass manufacturers specifically indicate their glazing systems are not intended for use in pressure-glazed curtain wall systems. Instead, the systems typically employ a glazing tape between the frame and the glass when setting the glass and potentially an additional bead of silicone sealant tooled to be water-shedding on the exterior face. Some manufacturers do not warrant the air and water integrity of a fire-rated curtain wall system if a primary perimeter sealant joint is only installed at the exterior pressure plates or cover caps.

Visual aesthetics and defects
The visual quality of any laminated glazing system will not match that of a non-laminated system, which uses the same glass components. The same holds true when the lamination is an intumescent product. In an effort to mitigate this difference, many manufacturers offer intumescent laminated systems with low-iron glass, which provides higher optical quality (i.e. greater light transmission and less color).

Intumescent laminated glass products are available with low-iron glass. However, sample warranties for these products also include language noting the impact of intumescent interlayers on optical clarity. One product warranty reads:

Due to the nature of its interlayers, (said product) may develop some minor imperfections such 
as small bubbles or a slight distortion which 
will not affect the free vision through the glazing or fire performance. A variation of up to 5% of light transmission or haze shall not be considered a defect.

fireglass_DSC05247

Figure 4: This photo displays creasing at the perimeter of the glass, which may occur at one or more of the interlayers.

Unfortunately, expected or allowable visual defects in intumescent laminated glass are not well defined in the United States. (See Figure 4 for an example of creasing and/or streaking.) International Organization for Standardization (ISO) 12543-6, Glass in Building–Laminated Glass and Laminated Safety Glass, Part 6: Appearance, is widely accepted throughout Europe, and several manufacturers base their in-house quality control guidelines on this standard. Currently, there is no equivalent standard published by ASTM or American Architectural Manufacturers Association (AAMA) for the United States. As a result, the only guideline by which to evaluate laminated glass is that offered by the manufacturers.

ISO 12453-6 divides the glazing material into a perimeter section, referred to as the ‘edge area’ and a remainder of the glass, referred to as the ‘vision area.’ The edge area is intended to be concealed by the frame, and therefore the standard allows for more defects in this portion of the glazing relative to the vision area (Figure 5). Published quality control literature for one manufacturer shows a modified version of the ISO 12543-6 (Figure 6).

Glass evaluation

Figure 5: Areas to be examined on finished sizes (of glass) ready for glazing, where 1 = width of edge area; 2 = edge area; 3 = vision area; H = height of pane; and L = width of pane. Image courtesy ISO 12543-6:2012

For a 2 x 2.5-m (6.5 x 8.2-ft) sheet of intumescent laminated glass, this modification effectively increases the size of the edge area by 42 percent, increasing both the total allowable defects in the glass and the likelihood those defects will be visible in service. This modification to the standard implies that the industry struggles with consistency and overall quality control, which places an increased burden on the contractors and design professionals involved.

Conclusion
Intumescent laminated glass can be an effective fire-resistive product, both aesthetically and functionally, for architects and building occupants. Intumescent glass products provide a level of fire-safety far exceeding that of other glazing products. These authors expect intumescent laminated glazing systems will continue to grow in market share in the future. With this growth, it is important building owners, contractors, and architects understand the limitations of these products to better inform their practices and clients, and building standards remain current with building technology.

fireglass_Manufacturer QC Diagram

Figure 6: This shows the modification to size classification of glass areas; this modification allows for an increase to the edge area, where numerous defects are allowed. Image courtesy Simpson Gumpertz & Heger

Until better industry standards for aesthetic quality are developed in the United States, these authors recommend design/construction professionals educate clients on the optical limitations of intumescent laminated glass before specifying those products. If a nearby project used this technology, one should take the client to see it firsthand. It is also recommended specifiers reference the existing European standard, ISO 12543-6, until local standards catch up.

Similarly, a typical curtain wall contractor will likely not understand the nuances of edge pressure and torque limitations or the sensitivity to water and UV of intumescent laminated glass until they experience it for themselves. The lack of industry experience with the installation (and handling) of these products underscores the value of a mockup, which should be created, especially for new products.

David E. Sacks, R.A., AIA, LEED AP, is a senior staff member in the Building Technology Division of Simpson Gumpertz & Heger (SGH), a national consulting engineering firm active in building rehabilitation, enclosure consulting, and structural engineering. He is experienced in the investigation and evaluation of building enclosures, including roofing, below-grade waterproofing, and wall and glazing systems, with a specialty in repair and rehabilitation of existing buildings. Sacks’ professional experience includes the investigation and restoration design of existing low-rise, mid-rise, and high-rise residential and commercial buildings, with exterior envelopes consisting of architectural terra-cotta, brick, stone, and modern curtain wall systems. He can be reached at desacks@sgh.com

Bradford S. Carpenter, PE, LEED AP, is an associate principal and vice-president in the Building Technology Division of SGH. He has more than 15 years of experience investigating, repairing, and designing building enclosure systems of all types. Carpenter is a member of the American Architectural Manufacturers Association (AAMA), a past co-chair of the Washington, D.C. Building Enclosure Council (BEC|DC), and a frequent speaker and author on building enclosure topics including design and performance. He can be reached at bscarpenter@sgh.com

Additional thoughts on the NAFS short-form specification

In the December 2014 issue of The Construction Specifier, Dean Lewis wrote about the North American Fenestration Standard/Specification for Windows, Doors, and Skylights’ (NAFS’) short-form specification. American Architectural Manufacturers Association/Window and Door Manufacturers Association/Canadian Standards Association (AAMA/WDMA/CSA) 101/I.S. 2/A440 serves as the basis for product certification as required by the International Building Code (IBC). Due to space constraints, two short ‘mini-articles’ were excluded from the final magazine’s layout. That information is now provided below.

ASTM and AAMA Standards
These are the ASTM standards and test methods cited in the 2011 edition of North American Fenestration Standard/Specification for Windows, Doors, and Skylights (NAFS). (All are assumed to be most current revision level unless otherwise cited.):

  • ASTM E283, Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen;
  • ASTM E330, Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights, and Curtain Walls by Uniform Static Air Pressure Difference;
  • ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference;
  • ASTM E547, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Cyclic Static Air Pressure Difference;
  • ASTM E987, Standard Test Methods for Deglazing Force of Fenestration Products;
  • ASTM E2068, Standard Test Method for Determination of Operating Force of Sliding Windows and Doors;
  • ASTM F588, Standard Test Methods for Measuring the Forced Entry Resistance of Window Assemblies, Excluding Glazing Impact; and
  • ASTM F842, Standard Test Methods for Measuring the Forced Entry Resistance of Sliding Door Assemblies, Excluding Glazing Impact.

American Architectural Manufacturers Association (AAMA) polymeric profile standards include:

  • AAMA 303, Voluntary Specification for Rigid Polyvinyl Chloride (PVC) Exterior Profiles;
  • AAMA 304, Voluntary Specification for Acrylonitrile-Butadiene-Styrene (ABS) Exterior Profiles Capped with ASA or ASA/PVC Blends;
  • AAMA 305, Voluntary Specification for Fiber-reinforced Thermoset Profiles;
  • AAMA 308, Voluntary Specification for Cellular Polyvinyl Chloride (PVC) Exterior Profiles;
  • AAMA 309, Standard Specification for Classification of Rigid Thermoplastic/ Cellulosic Composite Materials;
  • AAMA 310, Voluntary Specification for Reinforced Thermoplastic Fenestration Exterior Profile Extrusions;
  • AAMA 311, Voluntary Specification for Rigid Thermoplastic Cellulosic Composite Fenestration Exterior Profiles; and
  • AAMA 313, Voluntary Specification for Molded Aliphatic Polyurethane Elastomer Frame Materials.

Design Pressure vs. Performance Grade
In the past, the terms ‘Design Pressure’ (DP) and ‘Performance Grade’ (PG) have been loosely used by some in the field. The specific definitions of these terms have been carefully confirmed with the publication of American Architectural Manufacturers Association/Window and Door Manufacturers Association/Canadian Standards Association (AAMA/WDMA/CSA) 101/I.S. 2/A440, North American Fenestration Standard/Specification for Windows, Doors, and Skylights (NAFS).

Design pressure
Design pressure is a rating identifying the load induced by wind and/or static snow a product is rated to withstand in its end-use application—this is not to be confused with performance grade or structural test pressure (STP). Loads induced by static snow are applicable only to unit skylights, roof windows, and tubular daylighting devices (TDDs).

Performance grade
Performance grade is a numeric designator that defines the performance of a product in accordance with this standard/specification—this is not to be confused with DP or STP. PG is achieved only on successful completion of all applicable tests specified in Clause 5.

Structural test pressure
Structural test pressure is the pressure differential applied to a window, door system, TDD, or unit skylight. In this standard/specification, the STP is 150 percent of DP for windows and doors and 200 percent of DP for TDDs and unit skylights. This is not to be confused with DP or PG.

In other words, DP and STP are strictly structural qualifications, irrespective of the results of any air leakage resistance testing or water penetration resistance testing. On the other hand, the PG of a product is limited by the lowest/least performance of its structural, air leakage resistance, or water penetration resistance test results; operating force and/or forced-entry resistance requirements may also apply.

Fire-rated Glass Floor Captures the Light at Northwestern

At Northwestern University, this fire-rated glass floor provides a barrier to flames and smoke, but offers daylighting and a unique look. Photo courtesy Technical Glass Products

At Northwestern University, this fire-rated glass floor provides a barrier to flames and smoke, but offers daylighting and a unique look. Photo courtesy Technical Glass Products

Located in Evanston, Illinois, Northwestern University’s Engineering Life Sciences infill is a bright, multi-disciplinary space with collaborative gathering areas and cutting-edge classrooms, laboratories, and research rooms. The expansion rises five stories, bridging two of the campus’ existing building wings. It is designed to Silver standards under the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) program.

“The original building had courtyards that were turned into parking lots,” explains Matt Garrett, project architect at Flad Architects. “The infill makes use of this previously underused space and encourages interconnectivity with students and faculty in neighboring buildings.”

In implementing the infill design, Flad Architects faced the challenge of ensuring adequate, balanced light in the space, given the adjacent, existing building wings. This was particularly important in the nuclear magnetic resonance (NMR) lab and other ground floor areas, as too much direct sunlight could harm specialized instruments.

To allow for light penetration from the fifth floor to the ground floor, the design team desired a large, central atrium. It would allow light to spill down and throughout the building to promote student well-being. One potential setback with drawing light through the atrium was meeting fire and life safety codes. The firm needed a code-approved floor to divide the shaft into two segments, and to provide a barrier to fire and chemicals in the case of an accident. However, many of the floor systems that met these stringent fire and life safety codes were opaque fire-stopping materials such as concrete and corrugated steel.

To satisfy fire and life safety codes and help illuminate the infill, the design team used a fire-rated glass floor system comprising:
● two-hour fire-rated heat barrier glass;
● tempered, laminated walking surface glass; and
● steel framing grid.

It provides a barrier to flames and smoke, as well as radiant and conductive heat. During a fire, this capability ensures the glass floor system’s surface remains cool enough for individuals to walk across for the duration of its two-hour fire rating.

“We needed a fire barrier in the atrium, but we didn’t want researchers and students to be in the dark,” says Garrett. “The fire-rated glass floor system allowed us to compartmentalize a very large volume of space without blocking off access to daylight.”

The fire-rated glass floor system supports loads up to 732 kg/m2 (150 psf), which creates additional usable space in the project. The system’s textured, top-surface glass provides students and faculty with the necessary traction to walk across its surface without slipping. Use of ceramic-etched laminated glass means mild opacity, allowing the system to diffuse daylight from above the atrium down into the nuclear magnetic resonance ground-floor lab.

“The soft, milky appearance of the fire-rated glass floor system was really important from a daylighting perspective,” says Garrett. “Direct sunlight could damage the highly specialized instruments in the NMR lab. The pattern on the glass creates just enough opacity to allow for the transfer of soft, even light.”

Today, students studying on the fire-rated glass floor system can see the shape of instruments in the lab below. At the same time, the translucent glass provides privacy from ground-floor occupants looking up toward the light well above.

“It’s great to see the students are comfortable on the fire-rated glass floor. They have no hesitation to spend time studying on it,” adds Garrett.

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.