IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 Jablonka and Barrett | 55 Air Barriers Meet NFPA 285 – Burning Issues Marcus Jablonka and Peter Barrett Dörken Systems Inc. 4655 Delta Way, Beamsville, ON, L0R 1B4 905-563-3288 • mjablonka@dorken.com and pbarrett@dorken.com Marcus Jablonka has been vice president of his firm for nearly 10 years. He is a voting member of the ABAA Technical Committee and the ASTM E06 Committee on Performance of Buildings. He is also a member of the National Institute of Building Sciences (NIBS) and the Building Enclosure Technology and Environmental Council. Until December 2016, he served as president of the Building Envelope Moisture Management Institute (BEMMI). He holds a mechanical engineering degree from the University of Paderborn, as well as a graduate degree in business administration from the University of Bochum, Germany. Jablonka has contributed to many industry publications, including Interface. Peter Barrett is the product manager and marketing manager for his company, where he has been employed for over a decade. His involvement with the design community and building materials industry spans over 25 years. Barrett holds a B.A. (Hons.) from Queen’s University and an M.B.A. from Wilfrid Laurier University, and he currently serves on the board of directors for the Air Barrier Association of America (ABAA) and on its Audit Committee. He has also contributed to The Construction Specifier, Construct Canada, Tunnel Business, and Masonry Magazine. 56 | Jablonka and Barrett IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 ABSTRACT SPEAKERS The relationship between the air barrier/water-resistive barrier (WRB) and NFPA 285 (Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components) compliance is often misunderstood. We propose to add clarity by going beyond the standard misconception that one must consider NFPA 285 requirements only if the building is taller than 40 feet. While not necessarily new, the issues are broadly misunderstood, and assemblies not compliant with the building code are too often specified unknowingly. Based on the authors’ in-depth synthesis and analysis of information from a wide array of sources and experts, they will examine in detail the effects of insulation and cladding choices as they relate to selection of the WRB, as well as the membrane’s location within the wall system. This will be supported using real project detail drawings and specifications. In addition, manufacturer NFPA 285 compliance documentation, which can be difficult to interpret, will be examined for design and field use. IIBEC 2020 Virtual International Conve ntion & Trade Show | June 12-14, 2020 Jablonka and Barrett | 57 INTRODUCTION The trend toward higher energy efficiency, driven by stricter energy codes and increased resilience of buildings, continues to drive the evolution of the building construction industry. As the design of the building enclosure changes, so do the fire characteristics of wall assemblies. Significant contributing factors to the changes in fire performance are the deployment of new types of cladding material and the trend to include more insulation into the wall—specifically continuous insulation—which, in many cases, may be foam plastic based. An architecturally driven trend to use cladding materials with open joints adds further complexity to wall assembly designs. Not only do true openjoint cladding materials require the use of permanently weather-resilient barrier membranes and flashings, but they also alter the flammability of the wall assembly— in most cases, the flammability and fire propagation increase. The relevance of dealing with fire performance of wall assemblies under these evolving conditions can, therefore, not be taken lightly. National Fire Protection Association (NFPA) statistics show that from 2009 to 2013, U.S. fire departments responded to an average of 13,500 structure fires per year in high-rise buildings (seven stories above grade or higher). These incidents led to 40 civilian fire deaths, 520 civilian fire injuries, and $154 million in direct property damage.1 The industry trend towards increasing the energy efficiency of buildings has resulted in more stringent requirements for increased amounts of insulation in the wall cavity—in many cases, combustible materials. Building code requirements have been adjusted accordingly, now including noticeably more stringent fire protection provisions, thus bringing the importance of the test standard NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components, to the attention of product manufacturers, architects and specifiers, general contractors, and installers, as its importance and applicability has increased with every new edition of the International Building Code (IBC) in recent years. NFPA 285 requirements in the building code are not new; the Uniform Building Code (UBC) adopted an early large-scale test method and, with that, allowed the use of foam plastics in exterior walls of all construction types based on performance for the first time in 1988. The UBC subsequently adopted further evolved versions of the test in its 1992 version before NFPA 285 was published in 1998.2 Tests, however, are frequently not properly applied and test results and engineering evaluations are often misunderstood, misinterpreted, or misused, resulting in improper wall design that does not meet the code requirements. There is considerable discussion and confusion within the design and construction community regarding the specification of wall assemblies, including claddings, barrier membranes, insulation materials, etc. and whether the products or wall assemblies are NFPA 285-compliant. Earlier versions of the IBC and their sections on fire performance of wall assemblies were particularly focused on foam-based insulation materials, until newer code editions started to incorporate other wall assembly components as well (i.e., exterior claddings and WRBs). While the advent of fire-resistant insulation materials has contributed to potential reduction in flammability of wall assemblies, it has also added to the complexity of possible wall configurations, which all need to be individually tested for their fire performance. As of the 2012 version of the IBC, WRBs are also required to be part of the tested wall assembly to be permitted in Type I, II, III, or IV construction of buildings 40 ft. or higher. (See IBC Section 1403.5.) Frequently, architects find themselves challenged with obtaining clear and reliable information about individual products and wall components. Furthermore, there are no individual product tests that provide information on whether the products would meet the building code requirements with regard to fire performance of wall assemblies. The only way to prove that code requirements can be met is to submit the entire wall assembly with all its wall components to a large-scale NFPA 285 test. It is critically important to understand that NFPA 285 is an assembly test, not a material test. Either the entire assembly passes the code-defined requirements, or it doesn’t. An individual product or wall component (e.g., cladding, membrane, and insulation) cannot be considered “NFPA 285 compliant,” despite being a component of an “NFPA 285-compliant assembly.” The NFPA 285 test is designed to assess the fire performance of a specific wall assembly with all its components. Air Barriers Meet NFPA 285 – Burning Issues Not only do true open-joint cladding materials require the use of permanently weather-resilient barrier membranes and flashings, but they also alter the flammability of the wall assembly—in most cases, the flammability and fire propagation increase. The objective of this paper is to help designers and installers avoid misunderstandings and understand proper application and interpretation of test reports and engineering evaluation reports by accredited fire engineering firms to ensure that the chosen wall assembly design complies with fire-related building code requirements. NFPA 285 TEST – BRIEF SUMMARY The intent of the NFPA 285 test is to evaluate the fire propagation characteristics of exterior non-load-bearing wall assemblies. The two-story test involves two burners. One burner is placed inside a first-story test room; the second burner is placed in a first-story window opening. The test runs for 35 minutes and measures flame propagation and temperatures. Any observations made during the test are reported. The tested wall assembly is a minimum of 18 ft. high and 13 ft. 4 in. wide. To pass the NFPA 285 requirements, flames must not propagate more than 10 ft. from the top of the window opening, and must not propagate more than 5 ft. laterally from the centerline of the window. The tested wall assembly must not allow any flame propagation to the second-story room, and none of the measured temperatures in the wall assembly (exterior wall surface, wall cavity airspace, wall cavity insulation, stud cavity, etc.) must exceed 1,000°F. The authors want to point out that there are other specific details and criteria that have relevance with regards to the NFPA 285 test. As they have less relevance to the objective of this paper, they will not be elaborated on further. SITUATIONS WHERE NFPA 285 REQUIREMENTS MUST BE MET This section of the paper will provide a brief summary of the NFPA 285-related requirements in the IBC, and how a designer or specifier can determine whether the specified wall assembly requires testing. Under the IBC, NFPA 285 testing is not required if a wall assembly does not include foam plastic insulation and is less than 40 ft. above grade. NFPA 285 is also not required for Type V-B construction (combustible walls). In other words, buildings higher than 40 ft. that contain combustible claddings (i.e., metal composite material [MCM], high-pressure laminates [HPLs], fiberglass-reinforced polymer [FRP], exterior insulation finish systems [EIFSs]), and/or air and combustible WRBs, or buildings of any height that contain foam plastic insulation (other than Type V construction), trigger the requirement of NFPA 285 testing. The base wall structure (i.e., interior drywall, studs, exterior sheathing) may be non-combustible and, in that case, is not considered to be an NFPA 285 test trigger. However, these components still need to be taken into consideration as part of the complete wall assembly, as they can interact with other components and potentially be combustible. Therefore, individual wall components can significantly affect the overall fire characteristics of the complete wall assembly (Figure 1). Furthermore, the IBC prescribes that the wall components must meet the following requirements: • Flame spread index ≤ 25 (ASTM E84) • Smoke development index ≤ 450 (ASTM E84) • Maintain assembly fire rating (ASTM E119/UL 263) Non-combustible cladding materials, like concrete, brick, masonry, terra cotta, cementitious stucco, fiber cement boards, etc., do not, by themselves, trigger the requirement for NFPA 285 testing. MCM cladding systems are combustible, and their fire performance characteristics can vary greatly between different types and manufacturers. MCM cladding panels are between 3 and 25 mm thick and are available with open and closed joints. It is noteworthy that “open joints” are not truly open, but generally have a spline mounted behind and in between the panels, which prevents or reduces the penetration of rainwater and ultraviolet (UV) light past the cladding layer. The MCM panels, generally mounted over a girt structure, have a factory-bonded metal face and plastic core. Due to the large number of variables, every specific MCM product type by any manufacturer used within a specific wall assembly requires a separate NFPA 285 test. NFPA 285 testing is not required when MCM cladding is used on buildings less than 40 ft. height above grade, if its use does not exceed 10% of the building’s wall area when the separation between buildings is less than 5 ft., assuming that no foam plastic insulation is used in the wall assembly. FRP claddings are considered combustible composite materials made from a blend of polymers with reinforcing fibers laminated onto a wood or plastic core. When FRP cladding is used on buildings less than 40 ft. height above grade, NFPA 285 testing is not required if the use of these claddings is limited to 10% of the surface area of the wall when the separation between buildings is less than 10 ft., assuming that no foam plastic insulation is 58 | Jablonka and Barrett IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Figure 1 – NFPA 285 example wall assembly. used in the wall assembly. HPL claddings are exterior wall panels made from cellulose fibers bonded with a thermoset resin in a high-pressure lamination process. These cladding panels, typically between 4 and 15 mm in thickness, are available with open and closed joints. The “open joints” may be truly open but can also have a spline mounted behind and in between the panels that prevents or reduces the penetration of rainwater and UV light past the cladding layer. In case the requirement for NFPA 285 assembly testing is not triggered due to building height or use of foam plastic insulation for a particular wall assembly type that includes HPLs, the use of these claddings is limited to a 10% area of the wall if the separation between buildings is less than 5 ft. Due to the large number of variables, every specific HPL product type by any manufacturer used within a specific wall assembly will have different fire performance characteristics and, therefore, requires a separate NFPA 285 test. The new wall design incorporating the same wall component that was part of the previous test would have to be tested again. Air barriers and WRBs, including mechanically fastened building wraps, self-adhered membranes, and fluid-applied membranes, are considered combustible materials. These barriers can be installed behind or in front of the continuous insulation layer. The position may significantly affect the fire performance characteristics of the wall assembly. Therefore, each configuration of barrier and insulation layers requires a separate test. Different types of insulation commercially available in the market differ significantly with regard to fire performance and other performance criteria. When the insulation layer is installed on the exterior side of the base wall, it is considered “continuous insulation” as it will reduce the effect of thermal bridging due to steel studs on the overall R-value of the wall assembly. Mineral wool insulation has a nominal R-value of about 4 per inch. Extruded polystyrene insulation has an R-value of 5 per inch. Polyisocyanurate insulation has an R-value of about 5.6 per inch. On the other hand, mineral wool insulation is non-combustible and will therefore not serve as a trigger for the requirement of NFPA 285 testing. Furthermore, mineral wool is highly vapor permeable, allowing the wall assembly to rid itself of unwanted and harmful moisture via vapor diffusion. In contrast, foam plastic insulations are flammable and generally vapor impermeable or have a very low vapor permeability. Any change in wall assembly configuration requires a discrete NFPA 285 test. If a particular wall component (e.g., a specific WRB) has been used in a wall assembly that was tested to and has passed the NFPA 285 criteria, this component cannot be assumed to pass the test in other wall assemblies, and, vice versa, the already-tested wall assembly may not pass NFPA 285 requirements anymore if this component is substituted by another material. In such cases, a new test must be performed on a complete wall assembly. The same applies to any other changes to the wall assembly (e.g., changes in base wall configuration, changes of insulation type, cladding material, fastening systems, air gaps between wall assembly layers, etc.). Although some manufacturers may claim that they have an NFPA 285 test report for their product or wall component, caveat emptor applies since the product may have only passed one test in one specific wall assembly configuration. The architect or designer faces the challenge that the information on tested wall assemblies currently available is limited. He either needs to design a wall assembly that has already been tested and is known to pass NFPA 285 requirements, or the wall design of his choice needs to undergo a full-scale NFPA 285 test. This may bear the potential risk of not passing the requirements, therefore resulting in the need for redesign and further testing. Under certain circumstances, the use of a combustible WRB on buildings exceeding 40 ft. above grade may not trigger the requirement for wall assembly testing per NFPA 285; these include: • Walls in which the WRB is the only combustible component and the exterior wall has a wall covering of brick, concrete, stone, terra cotta, stucco, or steel with certain minimum thicknesses defined in the IBC • Walls in which: — WRB is the only combustible component in the wall — WRB meets the following criteria as per ASTM E1354: • Peak HRR <150 kW/m2 • Total HR <20 MJ/m2 • Effective heat of combustion < 18 MJ/kg — WRB has a Class A FSI/SDI • Other exceptions exist. However, they have little relevance in the context of this paper. Engineering judgments can be performed by licensed fire engineers. In many cases, this can save time and money, but the assessment of engineering judgments is limited to cases where less-flammable materials are being used in particular parts of the wall assembly compared to the case that has undergone a full-scale NFPA 285 test. It is also important to note that a local code official is not obligated to accept an engineering judgment and does have the right to insist on a report of a full-scale NFPA 285 test to prove that the wall assembly in question is code compliant. RISK AND POTENTIAL LIABILITIES WHERE NFPA 285 REQUIREMENTS ARE NOT MET As recent tragedies like the Grenfell Tower fire in London have demonstrated, decisions about façade components can have a significant impact not only on the building resilience, creating potential financial risk, but also can risk lives. Calamitous fires and occupant deaths are extreme examples of risk and liability, but they represent real risk and real outcomes nonetheless. More likely are consequences such as unforeseen cost increases and delayed construction schedules. If the goal is to complete the building correctly, on time, and on budget, understanding how wall component selection can trigger NFPA 285 compliance at the design phase is key. This will minimize surprises later in the process. It bears repeating that NFPA 285 compliance is a system approach, and that the system of products, rather than each individual component, must be compliant. It bears repeating because lacking this understanding leads to mistakes. Mistakes (i.e., not realizing NFPA 285 compliance is required) lead to additional cost and, particularly if not addressed, to additional risk and liability for all involved, the degrees of which will vary, depending on when the mistakes are detected. IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Jablonka and Barrett | 59 • During the design phase, the cost impact may be relatively low, leading to changes to wall details and the architectural specification. Cost, inconvenience, and schedule impacts are relatively minimal. • If the building is under construction, additional costs begin to increase dramatically. This is due to physical design changes, material waste, reordering of one or more new materials, and more labor. The construction schedule will be delayed, and someone will be held liable for all the additional costs. • Post-construction detection represents the highest levels of inconvenience, remediation costs, and potential liability. Complete tear-off, disposal, and replacement could run into the millions of dollars. If occupancy and use of the building are affected or the client loses business and revenue as a result, 60 | Jablonka and Barrett IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Figure 2 – A typical NFPA 285 Selection Guide. NFPA 285-COMPLIANT WALL ASSESMBLIES 2012 IBC The following assemblies meet the performance requirements of NFPA 285 (2012) as required by the International Building Code®. Wall Component 1 – Brick – Standard type brick veneer anchors, installed maximum 24 in. OC vertically on each stud. Maximum 2-in. air gap between exterior insulation and brick. Standard nominal 4-in.-thick clay brick, running bond patter, Type S mortar. 2 – Stucco – Minimum ¾-in.-thick, exterior cement plaster and lath. A secondary WRB can be installed between the exterior insulation and the lath. The secondary WRB shall not be full-coverage asphalt or butyl-based self-adhered membranes. 3 – Minimum 2-in.-thick natural stone (granite, limestone, marble, sandstone) or minimum 1½-in.-thick cast artificial stone veneer. Any standard installation technique can be used. 4 – Minimum 1½-in.-thick artificial cast stone. Any standard installation technique can be used. 5 – Minimum 1¼-in.-thick terra cotta non-open jointed. Any standard installation technique can be used. 6 – Minimum 1½-in.-thick concrete or precast concrete panels with a maximum 2-in. air gap between the exterior insulation and the concrete panel. Any standard installation technique can be used. 7 – Metal composite material Exterior Wall Covering – Use either 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 1 – Maximum 3-in.-thick foil-faced polyisocyanurate insulation. All exterior insulation board joints taped with foil tape or equivalent. 2 – Any noncombustible insulation material mineral wool insulation. If batts, can be either faced or unfaced. Exterior Insulation – Use either 1 or 2 1 – Product 1 2 – Product 2 3 – Product 3 4 – Product 4 5 – Product 5 Water-resistive Barrier Applied to Exterior Sheathing – Use either 1, 2, 3, 4, or 5 1 – ½-in.-thick, exterior type gypsum sheathing 2 – 5/8-in.-thick, exterior type gypsum sheathing Exterior Sheathing – Use either 1 or 2 1 – None 2 – Noncombustible insulation (fiberglass or mineral wool) faced or unfaced Cavity Insulation – Use either 1 or 2 1 – Concrete wall 2 – Concrete masonry wall 3 – One layer of 5/8-in.-thick Type X gypsum wallboard installed on the interior side of minimum 35/8-in. deep, minimum 20-gauge steel studs spaced at a maximum of 24 in. OC with lateral bracing every 4 ft. vertically. Minimal 4 lb/ft3 mineral wool insulation friction fit in each stud cavity and at each floorline. Base Wall System – Use either 1, 2, or 3 Materials someone will be accountable for those costs as well. • What if issues are detected, but no action is taken? One can just hope for the best. This probably represents the highest risk. While multistory buildings are considered to be safer than other buildings in the event of a fire,3 this doesn’t mean that they are without fire risk. Should a fire occur and the structure of the building is shown to be at fault, possible consequences include large fines and incarceration, as well as the personal responsibility for property damage and occupant death. Avoiding additional costs and liabilities necessitates designers moving beyond simply specifying what was specified on previous projects and staying current with building code requirements. Achieving NFPA 285 compliance will require consulting with multiple manufacturers about multiple products and requesting specific information. If the necessary information is not available or is not forthcoming, an alternate system may have to be selected because one may not just assume or guess at compliance. Architectural specification sections will have to be cross-referenced across the system components, since each will be listed in a different specification section. This same coordination will be needed for drawings and details. Not only must the correct products be chosen, but they also must be assembled correctly. Substitution requests can compound the intricacies further because it will need to be shown that the product being substituted will not alter the flammability or system compliance. Designers should work with suppliers who can help them be NFPA 285-compliant or can aid them when a system is not in compliance where it ought to be. Those suppliers are also helping to protect reputations and to avoid serious liabilities. UNDERSTANDING NFPA 285 COMPLIANCE DOCUMENTS NFPA 285 compliance of a wall assembly is based on the burning of a full-scale model wall. This establishes a baseline for the fire test data. Following that, smaller-scale tests on which engineering judgments can be based are made using ASTM E1354, Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using Oxygen Consumption Calorimeter, also known as the Cone Calorimeter Test. Manufacturers and suppliers of wall components receive long and detailed test reports for each full wall test and each small-scale engineering judgment from qualified fire engineering firms. While there is nothing inherently secret or wrong about releasing the full reports, manufacturers and suppliers generally do not because they can be confusing and do not synthesize information about various materials from more than one test. It should be noted that product manufacturers and suppliers cannot assert or claim compliance without reports as supporting data and cannot themselves assert project-specific compliance. This simply means no compliance to code requirements without an NFPA 285 test report or engineering evaluation as proof. Instead, product manufacturers and suppliers create Selection Charts within the confines of which a designer may pick and choose components to design a compliant assembly. The Selection Charts are based on the verified NFPA 285-compliant wall assembly reports. They are intended to guide architects, contractors, specifiers, consultants, and other interested parties on the assembly of an NFPA-285 compliant wall. Learning to properly decipher the Selection Chart makes specifying a compliant wall assembly considerably easier, though misinterpretation is still commonplace. There is no “official” method for displaying the information in a Selection Chart, but one format has come into common use. (See Figure 2.) Typically, the report is divided into two columns: Wall Component and Materials. The Wall Component column will list the wall part where the materials in the Materials section are to be used and will define the choices within that section. The Materials section lists the choices of materials that are acceptable for use as the particular wall component. It may also list some specifics or limitations for the use and application of a particular material (Figure 2A). Layer 1 – Define the Base Wall System This is where the primary wall components are selected. Often, choices are offered, but each will be non-combustible. Firestopping requirements may be included in this section or may appear as a separate layer, usually immediately following the base wall (Figure 2B). IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Jablonka and Barrett | 61 Figure 2A – Standard column headings. Figure 2B – Choices for a base wall system. NFPA 285-COMPLIANT WALL ASSESMBLIES 2012 IBC The following assemblies meet the performance requirements of NFPA 285 (2012) as required by the International Building Code®. Wall Component Materials 1 – Concrete wall 2 – Concrete masonry wall 3 – One layer of 5/8-in.-thick Type X gypsum wallboard installed on the interior side of minimum 35/8-in. deep, minimum 20-gauge steel studs spaced at a maximum of 24 in. OC with lateral bracing every 4 ft. vertically. Minimal 4 lb/ft3 mineral wool insulation friction fit in each stud cavity and at each floorline. Base Wall System – Use either 1, 2, or 3 Firestopping is shown as a separate layer (in this instance, labelled as “REQ” to indicate that it is required). (See Figure 2C.) Layer 2 – The Stud Cavity The basic choice is whether to have insulation or not. If the choice is in favor of insulation, the Selection Chart will list the options. While the insulation will most likely be non-combustible, one may select the type of insulation, such as mineral wool or fiberglass. Some systems may allow types of spray foam insulation, but those will be specific to a wall system. (See Figure 2D.) Layer 3 – Exterior Sheathing This will also be non-combustible and non-brand-specific. Depending on the requirements, choices may be items like thickness of sheathing, or even no sheathing. (See Figure 2E.) Layer 4 – WRB Applied to Exterior Sheathing A list of acceptable brands (i.e., product-specific) of WRB membrane will be listed here. The location where this list of membranes may be applied is a very key point. The WRB cannot be moved to another location in the system. As well, because a product is acceptable at this layer, it does not mean that it may also be used at another layer (e.g., WRB cannot necessarily be moved to the outside of continuous exterior insulation, should that be part of the wall design). This list is specific to use in this location only. (See Figure 2F.) Layer 5 – Exterior Insulation Choices of insulation materials listed may be non-combustible or combustible. Non-combustible keeps the system the simplest, allowing the broadest range of cladding options, and is usually mineral wool insulation. Combustible insulations could be either polyisocyanurate or extruded polystyrene to specified maximum thicknesses. It is critical to cross reference either of these choices with firestopping requirements and other special wall details like window headers. This will also affect the allowable claddings in the Exterior Wall Covering section. (See Figure 2G.) Layer 6 – WRB Applied to Exterior Insulation When a WRB is on the outer side of non-combustible insulation and behind non-combustible cladding, there are generally no issues. If the cladding is changed from non-combustible to combustible, the wall assembly becomes more flammable, and it therefore becomes more difficult to meet NFPA 285 criteria. Combine combustible cladding in front of a combustible WRB in front of combusti62 | Jablonka and Barrett IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Figure 2C – Example of required firestopping layer. Figure 2D – Insulation choices for the wall cavity. Figure 2E – Exterior sheathing options. Figure 2F – Typical WRB section would list options by brand, since different brands combust differently. Figure 2G – Insulation choices may have limitations on thickness. 1 – ½-in.-thick, exterior type gypsum sheathing 2 – 5/8-in.-thick, exterior type gypsum sheathing Exterior Sheathing – Use either 1 or 2 1 – Product 1 2 – Product 2 3 – Product 3 4 – Product 4 5 – Product 5 Water-resistive Barrier Applied to Exterior Sheathing – Use either 1, 2, 3, 4, or 5 1 – Maximum 3-in.-thick foil-faced polyisocyanurate insulation. All exterior insulation board joints taped with foil tape or equivalent. 2 – Any noncombustible insulation material mineral wool insulation. If batts, can be either faced or unfaced. Exterior Insulation – Use either 1 or 2 1 – None 2 – Noncombustible insulation (fiberglass or mineral wool) faced or unfaced Cavity Insulation – Use either 1 or 2 ble insulation, and it can become extremely challenging to meet NFPA 285 criteria. The challenge increases if the cladding is designed with true open joints, since this allows more oxygen into the space behind the cladding material. Should the WRB also be self-adhering, the adhesive would increase the combustibility of the wall system much further. Because the WRB appears acceptable in Layer 4, a designer cannot conclude that it will be acceptable in Layer 6. This will vary significantly with the combustibility of the insulation and/or the cladding. Layer 7 – Exterior Wall Covering This is sometimes called “exterior veneer.” The specifics of all the allowable claddings acceptable with the previous components are listed, including any requirements, such as minimum thickness, installation technique, mortar type, or attachment system. It is usually the largest section. It should be read carefully, as it will also contain any limitations on use with particular insulation choices. Due to variances in manufacturing, it may also limit brand choices. As an example, because one or two MCM panels are listed, it cannot be assumed that all MCM panels are acceptable, unless the document clearly says so. (See Figure 2H.) A given manufacturer’s document may have more or fewer choices, depending on the testing that has been done and the partners with whom they have chosen to work. The Selection Chart should be carefully read for special details that make the wall system effective. These may be additional firestopping at window headers or between floors. SUMMARY The relationship between the air barrier/WRB and NFPA 285 compliance is often misunderstood, and assemblies not compliant with the building code are too often specified unknowingly. The insulation choice and cladding choices as they relate to selection of the air barrier/WRB, as well as the membrane’s location within the wall system, are critical design considerations. The building code clearly defines under what circumstances NFPA 285 requirements must be met and when exceptions to these requirements apply. Selection Charts for designing NFPA 285-compliant wall assemblies can be confusing and difficult to read. However, correctly understanding them and the specific layers required is critical to designing a NFPA 285-compliant wall assembly. Unless the Selection Chart explicitly IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020 Jablonka and Barrett | 63 Figure 2H – Cladding options must be carefully considered because of wide ranges in combustibility. The insulation choice and cladding choices as they relate to selection of the air barrier/WRB, as well as the membrane’s location within the wall system, are critical design considerations. The building code clearly defines under what circumstances NFPA 285 requirements must be met and when exceptions to these requirements apply. 1 – Brick – Standard type brick veneer anchors, installed maximum 24 in. OC vertically on each stud. Maximum 2-in. air gap between exterior insulation and brick. Standard nominal 4-in.-thick clay brick, running bond patter, Type S mortar. 2 – Stucco – Minimum ¾-in.-thick, exterior cement plaster and lath. A secondary WRB can be installed between the exterior insulation and the lath. The secondary WRB shall not be full-coverage asphalt or butyl-based self-adhered membranes. 3 – Minimum 2-in.-thick natural stone (granite, limestone, marble, sandstone) or minimum 1½-in.-thick cast artificial stone veneer. Any standard installation technique can be used. 4 – Minimum 1½-in.-thick artificial cast stone. Any standard installation technique can be used. 5 – Minimum 1¼-in.-thick terra cotta non-open jointed. Any standard installation technique can be used. 6 – Minimum 1½-in.-thick concrete or precast concrete panels with a maximum 2-in. air gap between the exterior insulation and the concrete panel. Any standard installation technique can be used. 7 – Metal composite material Exterior Wall Covering – Use either 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 provides “none” as an option, all the layers must be included in exactly the order listed for the wall system to be compliant. Branded components listed in one layer of the Selection Chart cannot be assumed to be acceptable for use in another layer. This means, for example, that just because a specific WRB is compliant for use as the layer behind the insulation, it would not necessarily be compliant for use as the layer in front of the insulation. The most common misperception about Selection Charts is that if a branded product is listed anywhere in the chart, that it is, therefore, “NFPA 285 approved.” There is no such thing as an NFPA 285-approved product. In fact, using a product in a layer where it is not listed requires different testing or engineering evaluation in order to prove that the wall assembly is NFPA 285 compliant, and it renders the original Selection Chart inapplicable. It is exactly these types of misinterpretations that create liability, risk, and, in the most extreme cases, loss of life. The Selection Charts require focus to interpret correctly. If a designer is selecting components for a wall, one needs to be aware of when NFPA 285 compliance is triggered and exactly what must be done to be compliant. The onus is on the designer to know. Caveat emptor! REFERENCES 1. “NFPA U.S. High-Rise Building Fires Fact Sheet.” Fire Analysis & Research Division. https://www.nfpa.org/-/media/Files/News-and-Research/Fire-statistics-and-reports/Fact-sheets/HighRiseFactSheet.pdf 2. Barbara Horwitz-Bennett. “Navigating Wall Assembly Fire Testing.” DuPont. https://www.dupont.com/content/dam/assets/products-and-services/construction-materials/assets/Navigating_Wall_Assembly_Fire_Testing.pdf 3. “High-Rise Building Fires” NFPA. https://www.nfpa.org/-/media/Files/News-and-Research/Fire-statistics-and-reports/Building-and-life-safety/oshighrise.pdf. 64 | Jablonka and Barrett IIBEC 2020 Virtual International ConveVEntion & Trade Show | June 12-14, 2020
