Tag Archives: ASTM

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.

ASTM celebrates concrete centennial

Concrete Finishers

ASTM International’s concrete-focused committee has worked to improve the material’s use and durability for a century. Photo © BigStockPhoto/FrenchToast

During last month’s round of standards development meetings in Toronto, ASTM International celebrated the 100th anniversary of the group that became Committee C09 on Concrete and Concrete Aggregates.

Since 1914, when a small group gathered to work on methods for making and testing field specimens, C09 has grown to more than 1400 members from 62 countries, maintaining a portfolio of more than 175 standards. Its 50 subcommittees focus on aspects ranging from self-consolidating concrete and chemical admixtures to supplementary cementitious materials (SCMs) and pervious assemblies.

C09 has developed global standards in construction, industrial, transportation, defense, utility, and residential sectors, but the group says its first standard remains one of its most important. ASTM C94/C94M, Specification for Ready-mixed Concrete, was first approved in 1933, but has kept pace with technology changes to present day.

“Looking at C09’s book of standards doesn’t tell the complete story of the committee’s success and accomplishments over the past century,” said committee member Richard Szeczy (president of Texas Aggregates and Concrete Association).

lobo_colin_2014 (2)

Colin Lobo, PhD, F.ASTM, received the ASTM International Award of Merit for Service to Concrete Committee. Photo courtesy ASTM International

“To produce the defining concrete industry documents stakeholders around the world rely on every day has taken countless hours of dedicated effort and cooperation from thousands of international experts,” he continued. “Over the years, C09 has embodied everything that is great about the ASTM process. That itself is truly worth celebrating.”

In related ASTM news, Colin Lobo, PhD, has received the organization’s Award of Merit for Service to Concrete Committee (along with Fellowship). Chair of the ASTM Cement and Concrete Laboratory (CCRL) executive group and senior vice president of engineering for National Ready Mixed Concrete Association (NRMCA), Lobo was lauded for his contributions to specifications for concrete materials, test methods for fresh and hardened concrete, data evaluation, and laboratory assessment.

Wind Load and Air Barrier Performance Levels

Photo courtesy DuPont Building Knowledge Center

Photo courtesy DuPont Building Knowledge Center

by Maria Spinu, PhD, LEED AP, Ben Meyer, RA, LEED AP, and Andrew Miles

Continuous air barriers have become mandatory for the building envelope, with energy codes recognizing the importance of air leakage control. However, simple inclusion of an air barrier requirement does not guarantee the desired performance in the field. These systems must be properly installed, meet the building envelope structural wind loads, and maintain their function over time.

There are two accepted performance levels for commercial air barrier systems, determined by the structural design parameters for the building envelope:

  • ASTM E1677, Standard Specification for Air Barrier Material or System for Low-rise Framed Building Walls, applicable to envelope design specifications of up to 105-km/h (65-mph) equivalent structural loads; and
  • ASTM 2357, Standard Test Method for Determining Air Leakage of Air Barrier Assemblies, for buildings designed to withstand structural loads beyond that level.

This article describes the air barrier performance requirements for the desired wind load design specifications. The performance level is not determined by the type of air barrier material, but by the installation details. Examples of how these details can impact the performance level for a given air barrier system will be provided, with special emphasis on mechanically fastened air barriers.

Summary comparison between ASTM E1677 and ASTM E2357 wall assembly testing.

Summary comparison between ASTM E1677 and ASTM E2357 wall assembly testing.

Air leakage control and air barrier materials
Air leakage control is achieved through a continuous air barrier. Any material with an air permeance less than 0.02 L/(s • m2) @ 75 Pa pressure differential (0.004 cfm/sf @ 0.3 in. w.c. or 1.56 psf pressure differential), when tested in accordance with ASTM E 2178, Standard Test Method for Air Permeance of Building Materials, qualifies as an air barrier. Even though many common building products are air barrier materials (e.g. metal sheets, glass, oriented strandboard [OSB], and gypsum board), a continuous air barrier requires many compatible components to achieve a plane of airtightness. In practice, most air barrier materials are specifically designed membranes effectively integrated into a continuous air barrier system.

Testing of walls with mechanically fastened air barrier systems. Image courtesy DuPont and ATICommon air barrier materials include mechanically fastened (i.e. building wraps), fluid-applied, and self-adhered membranes. The choice depends on many factors, such as the substrate, desired performance level, installed cost, personal preference, local practices, and regional availability.

For example, in framed construction where air barriers are applied over exterior sheathing, building wraps are the most cost-effective. For masonry or concrete backup walls, fluid-applied membranes are the common choice. Self-adhered membranes can be used with either substrate, but most are vapor-impermeable and their use should be limited to specific climates and wall design options.

In the case of vapor-impermeable air barriers, the membrane plays a dual role: air and vapor barrier. While air barriers could be installed anywhere in the building envelope, vapor barrier location and use is climate- and design-specific. For example, vapor barriers are required only in cold climates, and must be installed at the ‘warm in winter’ side of the envelope. In warm-humid climates, a vapor barrier could still be acceptable to the outside of the envelope (where the air barrier is generally installed) when design options for drying pathways are available—such as when vapor-permeable materials must be used at least in one direction (in this example, everything to the inboard from vapor barrier must be vapor-permeable). Exulation wall design (i.e. exterior insulation only, no insulation in the stud cavity) can also use vapor-impermeable air barriers. Building physics must always be considered when an unintended vapor barrier is used in a wall assembly.

There are four essential performance requirements for air barriers:

  • air infiltration resistance;
  • continuity;
  • structural integrity; and
  • durability.1

Another critical property is vapor permeability, which could impact moisture management in wall assemblies. However, the codes do not specify the air barriers’ vapor permeance—the decision is left to the building envelope designer.2

CS_July_2014.inddAir infiltration resistance is an inherent material property for air barrier materials. Other requirements depend not only on material properties, but also on the performance of the installed system determined by the integration of air barrier components into a continuous system, as well as the durability under use conditions. In addition to the primary air barrier membrane, an air barrier system includes installation and continuity accessories, such as primers, mechanical fasteners, seam tapes, flashing, adhesives, and sealants.

This article mainly focuses on structural integrity requirement, which is the ability of an air barrier system to withstand wind loads experienced during the building’s use after construction is complete. There are two accepted performance levels based on building envelope design parameters with regard to wind loads and wind-driven rain. To establish the performance level of an installed air barrier system, air barrier wall assemblies must be tested in accordance with the respective ASTM standards.

Installed air barrier performance and wall assembly testing
Testing is essential for demonstrating performance of installed air barrier assemblies. This process is critical for developing robust installation guidelines for achieving air barrier performance levels consistent with structural design specifications.

As mentioned, ASTM E1677-11 applies to air barrier performance levels for building envelope design requiring up to 105-km/h (65-mph) equivalent structural loads, and up to 24-km/h (15-mph) equivalent wind-driven rain water infiltration resistance. This level is generally adequate for buildings of up to four or five stories, but higher performance is typically required on some low-rise structures like medical facilities and military buildings. ASTM E2357-11, on the other hand, applies to air barrier performance levels for building envelope design structural loads beyond this—such a performance level is generally necessary for buildings taller than five stories.

CS_July_2014.inddBoth test methods are performed on 2.4 x 2.4-m (8 x 8-ft) wall assemblies. ASTM E1677 requires testing of a single, opaque wall assembly (i.e. no penetrations except for the fasteners), while ASTM E2357 involves two specimen—an opaque wall and a penetrated wall that includes standard penetrations such as window openings, external junction boxes, and galvanized duct.

Both test methods require pressurization and depressurization testing, but use different pressure loads and schedules. The major differences between the two test methods are summarized in Figure 1, and consist of the pressure loads, schedule, and requirement for water infiltration resistance testing.

As shown, ASTM E1677 requires five test pressures:

  • ± 75-Pa pressure differential (1.56 psf, 25 mph);
  • two pressures below 75 Pa; and
  • two pressures above 75 Pa.
CS_July_2014.indd

Examples of window flashing for ASTM E2357 performance level.

The pressure loading schedule includes sustained loads of up to ±500 Pa (10.4 psf, 65 mph). This standard requires testing for water infiltration resistance per ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference. Air barriers or air retarders (as they are referred to in ASTM E 331) are classified as either Type I or Type II. Type I air barriers, which can also perform as water-resistive barriers (WRBs), must exhibit no water penetration when tested at 27 Pa (11 in. water pressure difference)—equivalent wind speed of approximately 24 km/h (15 mph)—during a 15-minute test period. Type II air barriers are not required to be tested in accordance with ASTM E 331.

ASTM E2357 requires a minimum of seven test pressures, from ±25 Pa (0.56 psf, 15 mph) to ±300 Pa (6.24 psf, 50 mph). The pressure loading schedule includes sustained, cyclic, and gust winds up to ±160-km/h (100-mph) equivalent wind speed. This standard does not require ASTM E331 testing for water infiltration resistance, which is a significant limitation since many air barriers are commonly required to also perform the WRB function and are exposed to pressure loads above 105-km/h (65-mph) wind.3

A building wrap air and water barrier system is installed over the exterior sheathing, prior to the installation of metal panels. Proper installation is critical for meeting the building envelope structural wind loads and maintaining the air barrier continuity over time.

A building wrap air and water barrier system is installed over the exterior sheathing, prior to the installation of metal panels. Proper installation is critical for meeting the building envelope structural wind loads and maintaining the air barrier continuity over time.

Air leakage results are reported at 75 Pa for both methods. Current codes require the average air leakage rate for air barrier assemblies must not exceed 0.2 L/(s•m2) @ 75 Pa pressure differential (0.04 cfm/sf under a pressure differential of 0.3 in. w.g. or 1.57 psf) when tested in accordance with ASTM E2357 or ASTM E1677.

Since a continuous air barrier experiences both positive and negative pressures during its use, it is important assemblies be tested under both positive and negative pressures. The negative load (under suction) is typically the most severe, as it tries to pull the air barrier off the wall. Different air barrier types have different susceptibility to negative pressure loads.4

For fluid-applied air barriers, wind loads are transferred to the substrate underneath. When the substrate is masonry or concrete, a fully adhered fluid-applied air barrier has excellent structural performance under suction, as the pressure it typically takes to separate it from the substrate far exceeds the actual pressure it must withstand.

However, for framed wall construction, the structural performance of fully adhered fluid-applied air barriers under negative wind loads depends on how well the sheathing is fastened to the building structure. When the exterior sheathing is not installed to withstand the design wind loads, this could reduce the air barrier system’s structural performance. In this case, the typical mode of failure for fluid-applied air barrier is the sheathing pulling over the screws.

CS_July_2014.inddIn comparison, when building wraps are installed over exterior sheathing, the air barrier membrane is supporting the entire load. Consequently, this type of air barrier is more susceptible to wind. The suction forces are transferred through the air barrier membrane to the mechanical fasteners, and then back to the structural supports (i.e. steel or wood studs). As a result, for a mechanically fastened air barrier, the wind load performance is determined by the type of fasteners and the fastener schedule.

The photos in Figure 2 show an example of high-pressure performance testing of commercial building wraps and exemplify the extreme forces experienced by the air barrier wall assemblies under negative pressure loads. The steel studs actually buckle under the pressure differentials used for high performance testing of building wraps (left), but a properly fastened building wrap withstands this pressure and maintains the system’s structural integrity (right).5

These pictures demonstrate the importance of proper fastening of building wraps to withstand high suction loads and maintain the air barrier structural integrity during use. A common mistake with building wraps installation is use of staples for fastening the building wrap into the exterior sheathing (a practice often employed for WRBs in residential construction), rather than employing recommended screws with washers to fasten the membrane into the structural members (wood or steel studs).

Building wrap manufacturers usually provide guidelines on the type of fasteners and the fastening schedule recommended for meeting the desired performance level. Figure 3 provides an example of fastening type and schedule guidelines and the maximum wind loads allowable.

Alternate fasteners are also allowed, when applicable. Examples include standard brick tie base plates and metal plates, metal channels, horizontal z-girts, and wood furring strips mounted vertically. They can be used in conjunction with the manufacturer-recommended fasteners to meet and/or satisfy the desired design performance.

In addition to fastener selection and spacing, other installation details are critical when designing for a specific performance level. Some building wrap manufacturers provide different installation details for ASTM E1677 and ASTM E2357. These include details on sealing of penetrations, transitions, and interfaces. For example, no additional fastener sealing is necessary for building envelope design requiring up to 105-km/h (65-mph) equivalent structural loads (i.e. ASTM E1677), when recommended fasteners and schedules are used. However, if higher air infiltration resistance is desired (i.e. ASTM E2357), self-adhered flashing must be used under the fasteners.

Figure 4 shows examples of alternate fasteners, as well as the use of self-adhered flashing under the fasteners for ASTM E2357 performance level. The same recommendations are also for fluid-applied membrane fasteners.

A mechanically-fastened air and water barrier system is installed over the exterior sheathing. Fluid applied air barrier was also used for concrete masonry unit (CMU) portions of this project (not visible in the picture). Proper integration between the two air barriers used for CMU and gypsum-covered metal stud walls was critical for continuity and structural integrity.

A mechanically-fastened air and water barrier system is installed over the exterior sheathing. Fluid applied air barrier was also used for  concrete masonry unit (CMU) portions of this
project (not visible in the picture). Proper integration between the two air barriers used for
CMU and gypsum-covered metal stud walls was critical for continuity and structural integrity.

Among the most critical details determining the air barrier structural performance level are windows and doors integration into the continuous system. Most manufacturers provide step-by-step window installation guidelines. Changes in the provider’s detailing and sequencing could change the performance level (i.e. ASTM E1677 or ASTM E2357). Figures 5 and 6 show examples of specific details for achieving the desired wind load design specifications.

The detail in Figure 5 shows how the window rough openings are treated with self-adhered flashing, for the high-performance level required by ASTM E2357. For example, when the building has non-flanged, storefront, and/or curtain wall windows, the air barrier membrane is typically cut flush with the edge or the rough opening. Then, the self-adhered flashing is installed to protect the rough opening and provide a positive termination of the air barrier membrane. The pictures on the right show examples of high-performance flashing for non-flanged and/or curtain wall windows that may be bumped out from the wall plane.

Figure 6 shows an example of window flashing for ASTM E1677 performance level. The picture captures the alternate head detail, which is generally allowed for building structures with building envelope design requirements not exceeding ASTM E1677. After the air and water barrier is wrapped into the window rough opening, a top hat is created with sealant to divert water away from the window opening (if the air barrier is also intended to serve as the WRB). WRB cut pieces are then installed (I) by wrapping in and around the studs at the jamb and the head, and stapling to inside framing to secure (A). The next steps include (II): (A) apply a continuous sealant bead along jambs and head, (B) install flanged window, (C) install jamb flashing, and (D) install head flashing.

A properly installed building wrap air and water barrier system is the most cost-effective option for this building with sheathing substrate and multi-story curtain wall consisting of brick and solid-surface cladding panels.

A properly installed building wrap air and water barrier system is the most cost-effective
option for this building with sheathing substrate and multi-story curtain wall consisting
of brick and solid-surface cladding panels.

The recommended installation guidelines are based on many wall assembly tests, and changing the installation details in the field could affect the performance level for the installed air barrier assembly. Engaging the air barrier manufacturers in early design stages is critical to understanding the installation details requirement and the optimal installation sequence to achieve the desired performance level. Additionally, it helps avoid unnecessary delays during the construction phase.

The difference between the two performance levels for air barriers is not always understood by industry professionals and installers, and not clearly stated by codes. For example, American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2013, Energy Standard for Buildings Except Low-rise Residential Buildings, Section 5.4.3.1.3.b, defines code-compliant air barrier assemblies as:

Assemblies of materials and components (sealants, tapes, etc.) that have an average air leakage not to exceed 0.04 cfm/sf under a pressure differential of 0.3 in. w.g. (1.57 psf) when tested in accordance with ASTME 2357, ASTM E1677.

As evident from this article, performance levels for ASTM E1677 and ASTM E2357 are not equivalent—nevertheless, ASHRAE 90.1-2013 provides the two options as equals. It is little wonder there is confusion in the industry, and the potential impact of changes to the manufacturer’s installation guidelines is not always appreciated.

A building wrap air and water barrier system is installed over the exterior sheathing, exterior insulation is installed over the air barrier, and exterior cladding (brick, metal panels, and solid surfacing) are installed to the outside.

A building wrap air and water barrier system is installed over the exterior sheathing, exterior insulation is installed over the air barrier, and exterior cladding (brick, metal panels, and solid surfacing) are installed to the outside.

Fortunately, Air Barrier Association of America (ABAA) recently introduced an evaluation process for air barriers, in order to apply consistent standards across the industry. On its website, the group lists the air barriers that have been evaluated and demonstrated to meet ASTM E2357 performance level. (For more, see “ABAA-evaluated Air Barrier Assemblies.”)

Current limitations of air barrier standards
Code requirements on air leakage control have led to a large increase in the number of materials claiming to perform as air barriers. The challenge with some airtight materials is in achieving a continuous and durable air barrier system. For example, many materials designed to perform other functions (e.g. thermal insulation or exterior sheathing) that are also resistant to air infiltration have been promoted as air barriers. While such products are adequate air barrier ‘materials,’ the long term continuity and durability of these air barriers as ‘systems’ is still an open question.

Some such materials have passed the current air infiltration resistance requirements for ‘as-installed’ air barrier assemblies per ASTM E2357 and are listed at the ABAA website. However, these systems may fall short of long-term durability under the use conditions. Additional testing, such as thermal cycling and water resistance, would be necessary to assess the long-term durability of these systems. This discussion is beyond the scope of this paper, but it should be of concern to the industry.

Conclusion
Building energy codes mandate a continuous air barrier for leakage control. The air barrier system must withstand the conditions a building is exposed to during its use. There are two acceptable performance levels for air barrier wall assemblies—ASTM E1677 and ASTM E2357—that are determined by the structural design parameters for the building envelope. Some air barrier manufacturers have developed two-tier installation guidelines for the desired level, and altering the guidelines could change the performance.

A fl uid-applied air and water barrier system is ideal for this building, which consists of multiple substrates and exterior claddings. The air barrier was installed over CMUs and gypsum board sheathing substrates; the multi-story curtain wall consisted of cut limestone on the fi rst fl oor, brick veneer on the upper fl oors, cast stone trim work, and perforated metal panels.

A fluid-applied air and water barrier system is ideal for this building, which consists of multiple substrates and exterior claddings. The air barrier was installed over CMUs and gypsum board sheathing substrates; the multi-story curtain wall consisted of cut limestone on the first floor, brick veneer on the upper floors, cast stone trim work, and perforated metal panels.

A major limitation of ASTM E2357 is the lack of water infiltration resistance requirement. Very few manufacturers integrate testing for ASTM E2357 air infiltration resistance with ASTM E331 water infiltration resistance of installed wall assemblies.

Current test methods are effective in measuring performance of newly installed air barrier assemblies under pressure differentials experienced by above-grade exterior walls and represent a huge step forward from relying solely on materials properties. However, current standards do not provide information about the long-term performance under field use conditions experienced by the buildings, which include seasonal and daily temperature variations.

The air barrier system performance is only as good as the weakest link, and differential expansion and contraction of multicomponent air barrier systems can compromise its continuity. Integration of rigorous structural integrity testing of air barrier wall assemblies with thermal cycling and water infiltration resistance will provide valuable information on the long-term durability of these systems.

Notes
1 These requirements have been described in various articles, including 2006’s “Air Barriers: Walls Meet Roofs,” by Wagdy Anis and William Waterston (www.shepleybulfinch.com/pdf/Air_Barriers_wall_meets_roof_final.pdf) and 2004’s “Air Barriers, Research Report,” by Joseph Lstiburek (www.buildingscience.com/documents/reports/rr-0403-air-barriers). Additional references can be found at the Air Barrier Association of America (ABAA) web site at www.airbarrier.org. (back to top)
2 The impact of air barriers’ vapor permeance on moisture management has been discussed by co-author Spinu in two other articles that were published in The Construction Specifier: April 2007’s “To Be or Not to Be Vapor-Permeable,” and November 2012’s “Designing without Compromise: Balancing Durability and Energy Efficiency in Buildings.” (back to top)
3 The wind loads and schedule considered in these tests have been developed by the ASTM standard committee. While the authors are not part of this committee, it is possible one of the reasons for developing multiple pressure loads is to extrapolate the data at low pressures through linear regression. At low pressure loads, the errors are larger than at high pressures, so it is important to have multiple data points. (back to top)
4 The standards assume the air barrier plane will take the full wind loads (even though this would only be true for pressure-equalized façades). (back to top)
5 The air barrier structural loading is based on the assumption the air barrier plane: (1) takes the full wind loads (even though this only occurs for pressure-equalized façade systems), (2) experiences thousands of cycles of high positive and negative pressure loads during its service life, and (3) experiences two severe storms in the first 15 years of service. The steel studs shown buckling in the picture are at the very high end of the pressure loads. The point is when proper fasteners and spacing are used, air barriers can perform under wind gust conditions. These tests are quite stringent, but air barriers must perform for the life of the building envelope and such conditions could be occasionally experienced. (back to top)

Maria Spinu, PhD, LEED AP, is a building scientist with DuPont Building Knowledge Center, where she has led global building science and sustainability initiatives for the commercial market for the past decade. She is the author of 16 patents and has been a speaker at many regional, national, and international conferences on building science and sustainability topics. Spinu can be contacted via e-mail at maria.spinu-1@dupont.com.

Benjamin Meyer, RA, LEED AP, is a building science architect with DuPont Building Knowledge Center, where he works with customers and industry associations to answer questions on commercial building envelope design. Meyer is on the board of the Air Barrier Association of America (ABAA), a member of the Materials and Resources Technical Advisory Group of LEED, and also a consultant of the ASHRAE 90.1 Envelope Subcommittee. He can be reached benjamin.meyer@dupont.com.

Andrew Miles is a forensics engineer, providing technical support as part of the DuPont Tyvek Specialist network. His responsibilities include mock wall testing and field investigations related to use, performance, and customer concerns. Miles can be e-mailed at andrew.s.miles@dupont.com.