Tag Archives: Water-resistive barrier

Durability of Water-resistive Barriers

wrb_file opener

Images courtesy Building Diagnostics

by Beth Anne Feero, EIT and David H. Nicastro, PE
Many new water-resistive barrier (WRB) products are being introduced, including liquid-applied membranes. These new products join traditional wraps, self-adhered membranes, felts, and building paper, making for a crowded marketplace. A WRB will be concealed behind cladding, where it cannot be inspected, maintained, or replaced, so it must last for the design life of the building. However, will the new products be durable?

WRBs are required by building codes, and are installed on nearly every building, so it is surprising the industry lacks standardized tests for many fundamental properties of WRB products. To evaluate their performance, 17 WRB products (new and old) were tested in various common construction details, along with accessory products (flashings, tapes, and sealants). This long-term study is ongoing, but has already yielded important observations.

Product selection
As its name implies, the purpose of a WRB is to stop liquid water from penetrating through a wall section. However, more products are sold as air barriers, with a corollary benefit of serving as a WRB—and, in some cases, as a vapor barrier. The products included in this study were confirmed with the manufacturers to function as WRBs, but their marketing literature does not always make that clear. As this industry is rapidly evolving, there is some confusion as to the terminology and functions of these products (Figure 1).

wrb_Fig 1 - rolling

Figure 1: This photo shows a water-resistive barrier (WRB) being applied—
or is it an air barrier? Or vapor barrier? Or weather-resistive barrier? Similar products are marketed differently and can have different capabilities, so the functions must be verified with the manufacturer. Images courtesy Building Diagnostics                                                                        

The 2012 International Building Code (IBC) states that in typical sheathing applications, “a minimum of one layer of No. 15 asphalt felt, complying with ASTM D226, Standard Specification for Asphalt-saturated Organic Felt Used in Roofing and Waterproofing, for Type 1 felt or other approved materials, shall be attached to the studs or sheathing.” A similar statement is found in the International Residential Code (IRC). For stucco and masonry veneer applications, both codes require wood-based sheathing “include a water-resistive vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.”

Many buildings are still being constructed with felt or building paper serving as the WRB. However, the industry is shifting toward products that can also serve as an air barrier—sometimes called ‘weather-resistive barriers.’ For their WRB function, these products have to be approved by building officials based on test reports demonstrating they perform as well as paper or felt. This does not seem like a very high bar, but it could be if durability were considered instead of just initial test results (Figure 2).

wrb_Fig 2 - WRB behind masonry

Figure 2: Once the masonry installation is complete, this WRB will be hidden, so it will need to last for the life of the building. The product was just introduced, but only long-term testing can verify design life.

Even if they provide only marginal waterproofing, paper and felt have been in service for decades, so their long-term behavior is well-established. By comparison, a few of the new WRBs have suffered various forms of product failure soon after application, resulting in manufacturers revising the formulations or application instructions (Figure 3).

wrb_Fig 3 - split joint

Figure 3: A WRB split at the sheathing joints before cladding was installed, which points to a concern about the robustness of thin barrier products. The manufacturer of this then-new product helped resolve the problem, and updated its recommendations for how to treat sheathing joints.

For this study, products were selected based on criteria that would be considered by designers and contractors for a multi-family building—one of the largest segments of the construction industry. (Most of these products would also be appropriate for large commercial projects, as well.) Research narrowed the products to those believed likely to continue to be sold in their present formulation—since some test results will not be attainable for several years, it would be pointless to invest in long-term testing of products that seemed questionable during the research phase. Additionally, products with a short allowable exposure time before cladding were eliminated because newer materials are being introduced with longer exposure time. As research indicates other viable products, they will be tested in the future.

Interpreting manufacturer’s instructions
Field investigations suggest most failures are caused by ‘what is on the outside of the can’—in other words, even the best products fail prematurely when the installation instructions are not clear (or followed). Sufficient information from the manufacturer is needed for correct use, including which accessory products are required and appropriate design details for typical penetrations, edges, and openings. Providing explicit, concise, and comprehensive instructions for the designer and installer is essential, but rare.

Before the test specimens were constructed, extensive time was spent researching the manufacturers’ publications. Some of the conditions being tested were not found in the instructions and details. For other products, there were multiple accessory choices that were not clearly defined, leading to possible wrong selections. For most of the products studied, it was necessary to contact the manufacturer to confirm the selections; in some cases, the technical support representatives contradicted the published information (and each other when both local and home-office personnel were contacted). While it is always a good design practice to involve the manufacturer, it would be better for the industry if these common details were clearly conveyed.

Another problem is some of the instructions provided are unrealistic. For example, several of the selected products require special detailing around brick ties, which is not economically viable (Figure 4). Voiding a manufacturer’s warranty is less of a concern than the potential for failures in systems that cannot self-seal such fastener penetrations.

wrb_Fig 4 - tie

Figure 4: This type of fussy detailing around brick ties is required by several WRB manufacturers, but it is not realistic. The cost, sequence of construction, and scheduling burdens would cause contractors to choose another product—or worse, not waterproof these frequent penetrations through the WRB as specified.

Ease of installation
Installers want WRB products that are easy and fast to install—to be economical, they want to avoid mixing multiple components, long drying times, multiple accessories, or fussy sequencing requirements. Keeping systems to the fewest products (such as a primary membrane for the field of the wall and a single accessory for detailing) reduces installation time and the possibility of errors.

The test products were installed by a specialty contractor, whose observations and comments indicated there was a wide range of difficulty in applying the products.

UV exposure rating
There are several new WRB products that are not sensitive to ultraviolet (UV) light, which would therefore make them good candidates to be used behind rainscreen cladding. These sophisticated, engineered cladding systems feature pressure-equalized compartments behind a veneer with permanently open joints, so it is important sunlight not damage the membrane through the joints.

For more common cladding systems, it is important to pay attention to the manufacturer’s published maximum exposure time for WRBs before they are covered with cladding. Interestingly, they each publish a single time limit (typically one to 12 months), but obviously the actual exposure during that period would vary depending on the climate and season. Therefore, the risk of prolonged exposure is uncertain.

Overall, the mockup specimens appear to be performing well, but some damage was already observed before reaching the claimed exposure limit. Most of the test specimens were first exposed in the winter; it can be expected the damage due to UV exposure would be worse if the testing started in the summer.

Contractors want longer exposure time, and the newest products being introduced claim to have this capability. This trend may tempt manufacturers into a marketing ‘arms race’ of sorts. During this research, some manufacturers changed their exposure rating without changing the formulation. The testing described below was designed to evaluate both the current exposure ratings and any increased timeframes claimed in the future. Although longer exposure time benefits the contractor, it is not clear benefit accrues to the owner.

Fire resistance
Performing fire testing is beyond the study’s scope, but the manufacturers’ literature typically addresses this requirement. With recent changes in code requirements (and more expected with the next IBC), water-resistive barriers are now being scrutinized for fire resistance in wall assemblies.

WRBs that are combustible and placed on a building over 12.2 m (40 ft) tall having a Type I−IV construction must be tested in an assembly that passes National Fire Protection Agency (NFPA) 285, Standard Method of Test for the Evaluation of Flammability Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components. A recent trend appears to be WRB manufacturers partnering with various other component manufacturers (including insulation, masonry anchors, and cladding) to create complete wall assemblies meeting this requirement.

Mockup test design
In the first phase of this study, WRB products were tested as part of a complete system. The research outlined above guided the design of mockup test specimens that represent most of the difficult details encountered on a typical project. Each specimen consists of a 0.9 x 0.6-m (3 x 2-ft) simulated wood stud wall segment with the WRB placed on plywood sheathing (except one product with an integral sheathing).

Each specimen contained multiple details a WRB system must be able to handle, as shown in Figure 5:

  • 
sheathing joint at the center (3.2-mm [1⁄8-in.] gap);
  • 
outside corner at the bottom and left edge;
  • window jamb flange at the right edge;
  • octagonal electrical junction box penetration;
  • large-diameter penetration (e.g. dryer vent);
  • small-diameter penetration (e.g. plumbing pipe); and
  • masonry veneer anchor (i.e. brick tie).
wrb_Fig 6 - Specimen Accessory Layout

Figure 5: The design of the mockup test specimens included many common details to explore the capability of each WRB system to seal them, as well as the manufacturer’s instructions. Accessory products were applied in strict accordance with the WRB manufacturers’ requirements. Image courtesy Classic Constructors LP

The details were sealed as required by each manufacturer—not based on what is commonly done in the field (Figure 6). While some of those requirements seem burdensome, the initial testing is intended to evaluate the system as recommended by the manufacturer.

The specimens were hung on metal racks facing solar south to be subjected to high solar radiation (in addition to wind and rain). They were placed vertically to simulate typical wall construction. Laying them back at an angle would have increased solar radiation to significantly accelerate the weathering, but it would eliminate another significant factor in performance: gravity. WRB products are often observed in the field to sag after exposure, which tugs on the flashings (Figure 7).

wrb_Fig 7 - detailing

Figure 6: As its name implies, the purpose of a water-resistive barrier is to stop liquid water from penetrating through a wall section. However, more products are sold as air barriers, with a corollary benefit of serving as a WRB. Image courtesy Classic Contractors LP

Once the specimens are exposed for their documented UV exposure rating, they are partially covered with a cement board to represent siding. This cladding is attached with screws, which tests additional fastener penetrations while also allowing the siding to be removed for observations. Only the top half of each specimen is covered; the bottom remains exposed to observe how the products deteriorate after the specified exposure time.

Clear rigid plastic was installed over the back of the specimens to prevent direct water entry, while allowing monitoring of any moisture penetration or damage from the front (product side). A metal coping protects the top of each specimen, but it is not sealed to the cladding—water can enter above the cladding so the WRB will be wetted by rain even after the cladding is applied (the essence of a WRB).

wrb_Fig 8 - sag REPLACEMENT PHOTO

Figure 7: The flashing sagged at the bottom of this wall. Gravity is a factor in WRB system durability, so long-term test specimens at The Durability Lab are therefore vertically oriented. Photo courtesy Buildings Diagnostics

Besides the large mockup specimens, additional small ones are being tested for material properties, including adhesion, that are beyond this article’s scope. Other small specimens are used for the nail sealability testing described below.

Conclusion
Improving durability requires addressing long-term behavior, which is typically related to weathering and chemical formulation. These aspects of a product’s ‘design life’ will be evaluated during the long-term testing described above; a future article will summarize those findings after sufficient exposure. Some premature failure has already been observed, which indicates the need to be vigilant in product selection regarding claimed exposure ratings.

The research and mockup testing also were designed to evaluate a product’s ‘service life,’ which is often governed by the original installation. The results so far indicate the industry needs better information, instructions, and details from manufacturers. To be economical and durable, an ideal WRB system would include only a few required products that are easy to install, cure rapidly, adhere well, seal around fastener holes, and withstand UV exposure for an extended time. None of the products tested so far met all of these criteria.

The industry also needs standard test methods and product specifications that are applicable to WRBs (and air barriers). Some of these are in development by professional societies, but those will take time to develop. Meanwhile, specifiers should be aware the tests cited by manufacturers may not be applicable to the performance criteria needed for a WRB. Most notably, a product’s claimed ability to seal around fasteners should be scrutinized—this study revealed the test methods and published information are generally unreliable regarding this fundamental property of WRBs.

Note: The authors gratefully acknowledge the continuing support and leadership of David W. Fowler, PhD, PE—the faculty advisor for the research being performed at The Durability Lab, a testing center at The University of Texas at Austin.

 Nail Sealability
wrb_Fig 5 - nail test

ASTM nail sealability testing for roofing products is often cited by water-resistant barrier (WRB) manufacturers. This severe test consists of checking for leaks after driving two nails through a waterproofing product applied to plywood, filling a cylinder with 125 mm (5 in.) of water, and chilling the entire specimen for three days. (An environmental chamber at The Durability Lab is visible in the background.) Image courtesy Building Diagnostics

One of the most important—and least understood—durability characteristics of a waterproofing material is its ability to seal around fastener penetrations. Since there is no industry standard for water-resistive barriers (WRBs), this property is commonly measured by ‘borrowing’ a roofing material specification: ASTM D1970, Standard Specification for Self-adhering Polymer Modified Bituminous Sheet Materials Used as Steep Roofing Underlayment for Ice Dam Protection. Many WRB manufacturers publish that their products pass this test; others are silent about nail sealability.

ASTM D1970 was changed in August 2014 to reference a procedure in ASTM D7349, Standard Test Method for Determining the Capability of Roofing and Waterproofing Materials to Seal Around Fasteners. Although better than the previous method, this is still a ‘borrowed’ roofing standard that requires modification for testing WRBs.

The revised test method, which is still severe, requires placing the membrane onto a piece of 12-mm (15⁄32-in.) thick plywood, 300 x 300 mm (12 x 12 in.). Two roofing nails are driven into the center of the board until they are flush with the membrane. Under the old method, the nails would then be tapped back off of the board 6 mm (1⁄4 in.), but now they remain flush.

After cutting its bottom out, a 4-L (1-gal) paint can is placed atop the membrane over the nails and sealed with silicone. The can is filled with water to a height of 125 mm (5 in.). 
An additional can is placed underneath to catch any leaking water, and this entire specimen is put in a temperature controlled chamber at 4 ± 2 C (39.2 F ± 3.6 F) for three days.

After testing, the specimen is removed to observe any water penetration underneath the membrane, on the plywood, on the shanks of the nails, and in the can beneath the plywood. If moisture is documented in any of these locations, then the test is considered a failure.

Fluid-applied membranes cannot explicitly follow this procedure because it requires the membrane to be removed from the plywood substrate for observation. Additionally, the test method assumes an intervening material (typically a shingle for roof product testing) is placed between the nail and the specimen. It is common to modify the test method to suit the product being tested, but it is difficult to find out what modifications manufacturers made.

The new procedure in ASTM D1970 now requires all completed tests to be reported as a ‘pass’ or ‘fail.’ This seemingly straightforward requirement addressed a significant problem: some manufacturers were performing tests until reaching two passing results, and only reporting those two results. Specifiers should confirm with the manufacturers whether products claiming to “pass D1970” included failed tests and what deviations were made from the latest published test method.

The standard does not explicitly define ‘self-sealing,’ so it is useful to compare similar terms. One manufacturer defines self-sealing as “Capable of sealing itself, as or after being pierced.” This is the closest term for the property needed in a WRB—the ability to self-seal around a fastener penetration without an additional application procedure. That same company defines a ‘self-healing’ material as one with “the structural incorporated ability to repair damage caused by mechanical usage over time.” This is not a common feature of WRB products, but the term is often erroneously used as a synonym for self-sealing.

Another manufacturer refers to a similar term, ‘self-gasketing,’ as “the membrane’s ability to be cut by the threads of a self-drilling screw, then seal under compression (i.e. the screw head compresses the membrane as it is seated providing a positive seal).” This term represents an evolving trend in the industry to downplay intrinsic self-sealing capability in favor of extrinsic gasketing provided by another material compressed over the penetration. Some published requirements for products to achieve self-gasketing would not be possible in an actual wall assembly, so specifiers should be aware of the changing terminology and its implications.

Clearly, these definitions express different characteristics of a membrane’s nail sealability either with the nail, without the nail, or based on the compression of the fastener, respectively. Such a distinction implies whether a secondary sealant, protective coating, or intervening material is needed to seal around fasteners.

ASTM D1970, together with its reference to D7349, provides a direct measurement of self-sealing capability. It is a severe test, it was developed for roofing products, and some modifications are needed to test WRBs. These factors may explain why the standard is not cited by all manufacturers; however, self-sealing is crucial, and should be evaluated for any WRB.

ASTM nail sealability testing for roofing products is often cited by water-resistant barrier (WRB) manufacturers. This severe test consists of checking for leaks after driving two nails through a waterproofing product applied to plywood, filling a cylinder with 125 mm (5 in.) of water, and chilling the entire specimen for three days. (An environmental chamber at The Durability Lab is visible in the background.)

Beth Anne Feero, EIT, is a graduate student studying architectural engineering at the University of Texas at Austin. She serves as the graduate research assistant for The Durability Lab, which researches and tests the durability of building components, identifying factors causing premature failure. She can be reached via e-mail at bfeero@buildingdx.com.

David H. Nicastro, PE, is the founder of Building Diagnostics Inc., specializing in the investigation of problems with existing buildings, designing remedies for those problems, and resolving disputes which arise from them. He is a licensed professional engineer, and leads the research being performed at The Durability Lab—a testing center established by Building Diagnostics at the University of Texas at Austin (UT). He can be reached by e-mail at dnicastro@buildingdx.com.

WRB: Water (or Weather?)-resistive Barrier

slaton patterson sutterlinFAILURES
Deborah Slaton, David S. Patterson, AIA, and Jeffrey N. Sutterlin, PE

Using the acronym ‘WRB’ is common, but the intended meaning is often misunderstood, as it can refer to either a ‘water’ or ‘weather’-resistive barrier, with the two having different performance expectations.

The 2012 International Building Code (IBC), Section 1403.2−Weather Protection requires exterior walls “provide a building with a weather-resistant exterior wall envelope…designed and constructed… to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer.” Water-resistive barriers are defined in Section 1404.2 as “a minimum of one layer of No. 15 asphalt felt, complying with ASTM D226, Standard Specification for Asphalt-saturated Organic Felt Used in Roofing and Waterproofing, for Type 1 felt or other approved materials…to provide a continuous water-resistive barrier behind the exterior wall veneer.”

For adhered stone veneers, Section 1405.10.1.1 requires water-resistive barriers to be installed per section 2510.6, which in turn directs the reader back to Section 1404.2, but adds the requirement the water-resistive barrier be vapor-permeable with the equivalent performance of two layers of Grade D paper when applied over wood-based sheathing. (Section 2510.6 of the 2015 IBC has been revised to require a vapor-permeable barrier with performance at least equivalent to two layers of a water-resistive barrier complying with Type I of ASTM E2556, Standard Specification for Vapor Permeable Flexible Sheet Water-resistive Barriers Intended for Mechanical Attachment, which includes polymer-based barriers.) It should be noted IBC’s Chapter 14−Exterior Walls does not reference weather-resistive barriers.

The American Architectural Manufacturers Association (AAMA) defines weather-resistant (not ‘resistive’) barriers as a surface or a wall responsible for preventing air and water infiltration to the building interior. Manufacturers of polymer-based barriers (i.e. building wraps) also distinguish between water-resistive and weather-resistive barriers, with the latter providing the added benefit of also serving as an air barrier for the vertical building enclosure.

While not as potentially destructive as bulk water leakage, moisture transport via air infiltration can contribute to moisture-related problems in the building enclosure. Weather-resistive barriers are often more robust as compared to water-resistive barriers and require taping of all laps and terminations to resist not only water penetration, but also air infiltration.

Code-mandated water-resistive barriers are typically limited to residential and low-rise structures, while weather-resistive barriers are commonly specified for commercial buildings or projects where a higher level of performance is desired of the vertical building enclosure and control of interior environmental conditions is critical.

It is important the design professional and installer understand the intended purpose of the specified WRB—to resist water or to resist air and water—as the installation varies between the two types of barriers. However, regardless of whether the WRB is intended to function as a water- or weather-resistive barrier, the WRB must be properly installed so as to maintain continuity of the barrier. This requires the WRB to be properly integrated with flashings, wall openings, and all adjacent enclosure assemblies, and to be sufficiently overlapped, correctly shingled, and properly sealed or taped at exposed laps (horizontal and/or vertical, depending on its intended purpose), as barrier discontinuities result in potential entry points for water (and air) to migrate into the building.

The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect those of the CSI or The Construction Specifier.

Deborah Slaton is an architectural conservator and principal with Wiss, Janney, Elstner Associates, Inc. (WJE) in Northbrook, Illinois, specializing in historic preservation and materials conservation. She can be reached at dslaton@wje.com.
David S. Patterson, AIA, is an architect and senior principal with WJE’s Princeton, New Jersey, office, specializing in investigation and repair of the building envelope. He can be e-mailed at dpatterson@wje.com.
Jeffrey N. Sutterlin is an architectural engineer and senior associate with WJE’s Princeton office, specializing in investigation and repair of the building envelope. He can be contacted via e-mail at jsutterlin@wje.com.

 

Exterior Wall Assemblies: Are you getting what you specified?

All photos courtesy Dryvit Systems Inc.

All photos courtesy Dryvit Systems Inc.

by J.W. Mollohan, CSI, CCPR, CEP, LEED GA

The exterior wall assembly of a building typically results from the integration of numerous individual building—materials from different manufacturers that are installed by multiple trades and subcontractors.

Generally, the specifier selects a basis of design (BOD) for these wall components, drawn from previous experience and trusted advisors’ recommendations. The specifier may also include a list of comparable material options from alternate manufacturers. However, when this process reaches the bidding stage, the design team loses control of which products are selected.

This common practice raises some practical questions. Who is responsible for determining and confirming the installed products are code-compliant as a complete exterior wall assembly? Will this particular wall assembly satisfy the more stringent requirements of the 2012 International Building Code (IBC) and International Energy Conservation Code (IECC)? These codes address multiple and overlapping issues of thermal, moisture, air, and fire performance for both the individual materials as well as specific assemblies of those materials.

When it comes to fire safety, IBC references National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components.1 This is the standard for fire testing in exterior walls when combustible materials such as foam plastic continuous insulation (ci) and water-resistive barriers (WRBs) are components within the wall assembly.

The stringent and expensive test provides a specific method of determining the flammability characteristics of complete exterior, non-load-bearing wall assemblies/panels. It is intended to evaluate the inclusion of combustible components within wall assembly panels of buildings otherwise required to be of non-combustible construction. As such, the test is designed to emulate the actual fire-resistance performance of the wall assembly in a constructed building.

NFPA 285 compliance is required for Type I–IV commercial buildings of two stories or more where exterior wall assemblies integrate combustible claddings, veneers, and/or foam plastic insulations. For 2012 IBC, WRBs must now also be NFPA 285-compliant for commercial buildings of Type I–IV construction when integrated within wall assemblies above 12 m (40 ft) in height. Whether cited in the specification or not, the test requires the specific assembly of products and materials intended to be installed in the wall is tested to comply.

Typical components of an exterior insulation and finish system (EIFS) system.

Typical components of an exterior insulation and finish system (EIFS) system.

Multiple choice specifications
As already noted, specifiers stipulate what is needed, but commonly accept any combination of competitive materials meeting the same performance criteria. The contract documents convey the design intent to comply with code, or more specifically to comply with NFPA 285. Should this responsibility be transferred to a general contractor or sub-trade? Who is ultimately liable for determining whether the as-installed assembly has been tested and complies? And, at what project stage is this going to take place: pre- or post-bidding?

Everyone wants to minimize the risk of a non-compliant assembly being installed. A code enforcement official requiring a test of the as-bid assembly can create prohibitive additional costs and delays.

This can be extremely complicated, as traditional foam plastic continuous insulation and WRBs may be standalone products with limited, if any, testing as a complete wall assembly. As a result, some manufacturers of these components are attempting to create alliances with various cladding manufacturers to test and offer ‘typical’ code-compliant assemblies.

However, this level of cooperative testing is limited and may not be acceptable to some jurisdictions where attempts are made to simply ‘blend’ individual materials or ‘similar’ assembly test reports together to represent the project specific wall assembly. This may also leave owners and designers questioning whether the general contractor can provide a wall assembly solution composed of individual materials both compatible with one another and code-compliant, from all the possible specified or substituted variations and combinations. That uncertainty is multiplied by separate sub-contractors installing the various components of the exterior wall assembly. It is difficult for the project team to have confidence the constructed exterior walls will satisfy the specifications’ requirement of a code-compliant assembly.

EIFS provide continuous insulation (ci) to meet the latest code requirements, such as National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components in a wide variety of architectural finish options.

EIFS provide continuous insulation (ci) to meet the latest code requirements, such as National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-load-bearing Wall Assemblies Containing Combustible Components, in a wide variety of architectural finish options.

Specify and install tested assemblies
Rather than exposing the owner to these risks, the project team can identify a sole source responsible for manufacturing, testing, and warranting the complete exterior wall assembly from the sheathing out. Such complete single-source wall assemblies offer the greatest likelihood the installed system will truly meet the design team’s intent, as well as requirements for code compliance, material compatibility, and specified performance. The alternative is to fully test the proposed wall assembly at substantial cost and time in the hopes it will pass.

An exterior insulation and finish system (EIFS) is a prime example of this type of single-source assembly. Structural wall components, such as exterior framing and sheathing, are already in place at the site before application of the EIFS. A single subcontractor then installs the system’s components, often in a single mobilization. All the EIFS components are sourced from a single manufacturer who can offer exhaustive testing, code compliance, and solid warranties on the systems’ quality and performance. The result is a lightweight, high-performance, and code-compliant exterior wall assembly.

Modern exterior insulation and finish moisture-drainage systems meet all current building and energy code requirements through their integration of proprietary WRBs, compatible flashings, continuous insulation, and integrated detailing for the development of continuous air barriers. Additionally, the systems include a finish surface available in various styles, colors, and aesthetic appearances such as stucco, brick, limestone, granite, and metal.

In this project a single-source system with a metallic finish was used.

In this project a single-source system with a metallic finish was used.

EIFS thicknesses, variations, and details are extensively tested and can be installed over a broad range of commonly available structural and non-structural wall substrates in both new construction and renovation.

The benefits of this single-source system include:

  • ease of specification;
  • greater control of the bidding and construction processes;
  • simplified contract administration;
  • improved coordination of entire exterior wall components; and
  • conformance with all aspects of code requirements and architectural design.

Case study: Metro Career Academy
It is not an overstatement to say clay brick masonry is the foundation of modern Oklahoma City. The look of brick and stone masonry continues to be popular with area architects and building owners everywhere. However, the ever-increasing demands of climbing construction costs, energy efficiency, and lifecycle performance led architect Fred Quinn (Quinn & Associates) to research different materials to meet the demands of the high-performance Metro Career Academy (MCA).

The original design of the MCA building called for 2229 m2 (24,000 sf) of clay brick and 1207 m2 (13,000 sf) of cast stone. When Quinn learned he could use an EIFS for the same look and save nearly 50 percent in construction costs versus the clay brick and stone, it was an easy decision.

In addition to this dramatic reduction in cladding costs, making the decision to switch to EIFS during the schematic design phase, allowed the owners of the Metro Career Academy to harvest the full range of benefits from the lightweight cladding, including:

  • less structural support;
  • reduced construction schedule; and
  • projected energy savings and fewer delivery trucks (i.e. reduced environmental impact).

By substituting the 0.07 kPa (1.5 psf) adhesively-attached EIFS with moisture drainage system for the labor-intensive 1.9 kPa (40 psf) masonry and stone, the designer was able to subtract more than 96 percent of the anticipated weight of the building’s skin. Eliminating 646,142 kg (1,424,500 lb) from the exterior walls of the building produced additional savings in the concrete and steel support system required to carry that initially designed load.

Metro Career Academy utilized products to simulate the brick and limestone found throughout the red river area.

Metro Career Academy utilized products to simulate the brick and limestone found throughout the red river area.

Cris Callins, manager of preconstruction with general contractor CMS Willowbrook, estimated the reduced demand for structural support and the rapid installation of the EIFS system allowed the project manager to cut a full 15 weeks from the MCA building’s construction schedule, lowering labor, equipment, and insurance costs while easily meeting the owner’s demanding completion date.

The project used 101.6 mm (4 in.) of exterior continuous insulation (ci) as part of the single-source EIFS system. This helped MCA achieve Leadership in Energy and Environmental Design (LEED) Gold certification. The project earned the full 10 points in the Energy & Atmosphere (EA) Credit 1, Optimize Energy Performance. The computer-modeled performance anticipates an energy usage savings of 34.8 percent and an energy cost reduction of 42.8 percent annually compared to the baseline. Without taking into consideration rising costs of energy or inflation, it is possible to conservatively estimate the value of these energy savings over a 50-year lifecycle of the MCA facility at more than $1.7 million.

Overall, the EIFS assembly allowed the entire project team to increase the insulation value of the wall, enhance the moisture protection of the building envelope, and lower the cost of the exterior cladding, while retaining the desired look of masonry and stone. The single-sourced, fully-tested system meets all of the new code requirements, including NFPA 285.

The Gaylord Palm Hotel in Kissimmee, Florida employed a single-source EIFS.

The Gaylord Palm Hotel in Kissimmee, Florida employed a single-source EIFS.

Conclusion

Everyone involved in the design and construction process has an interest in ensuring installed exterior wall assemblies match the specifications. As demonstrated, this means the assembly must be tested as a complete system. Whatever the authority having jurisdiction (AHJ), the code enforcement official has the right to demand proof of testing compliance in the interest of protecting the public. The licensed design professionals on a project have a similar right to demand compliance with the specifications on behalf of the owner who is paying for a compliant building all in the interest of protecting

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the health and safety of building occupants.

Delivering exterior wall systems through a single-source solution for manufacturing, code compliance, and warranty, is a proven method of assuring these desired outcomes. In addition to creating a high-performance system, this approach saves time and money for all parties. Perhaps most importantly to all of us, it yields an installed exterior wall system that can readily meet the complete quality and performance standards of the specifications.

Notes
1 For more on this standard, see the article, “Specifying NFPA 285 Testing,” by Joseph Berchenko AIA, CSI, CCS. (back to top)

J.W. Mollohan, CSI, has 30 years of experience in the design and construction industry, and is currently a strategic markets manager at Dryvit Systems Inc. He is a member of the Leadership Team of the Kansas City Building Enclosure Council (BEC), and president of the North Central Region of the Construction Specifications Institute (CSI). Mollohan chairs CSI’s national membership committee. He can be reached at jw.mollohan@dryvit.com.