{"id":125033,"date":"2020-12-02T09:59:46","date_gmt":"2020-12-02T14:59:46","guid":{"rendered":"https:\/\/www.constructionspecifier.com\/?p=125033"},"modified":"2020-12-02T10:17:59","modified_gmt":"2020-12-02T15:17:59","slug":"continuous-insulation-performance","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/continuous-insulation-performance\/","title":{"rendered":"Continuous insulation performance"},"content":{"rendered":"
\"Photo<\/a>
Photo \u00a9 BigStockPhoto.com<\/span><\/em><\/figcaption><\/figure>\n

by Marcin Pazera, PhD<\/strong><\/p>\n

The goals of building fire safety and energy efficiency are compatible when industry stakeholders work together to make sure proper assemblies are designed, the correct materials are specified, and installers have the experience to combine the building design and materials properly in the field.<\/p>\n

Building occupant safety is always a top priority. Incorporating redundant fire protection measures and strategies during a building\u2019s design and construction can minimize fire risks and limit the potential harm to people and loss of property when fires occur. While the cause and intensity of every fire is different, the fire-safety measures required by today\u2019s building codes (e.g.<\/em> fire suppression systems, building egress requirements, fire-resistive assemblies, and construction material fire test standards) are tools professionals can use for a balanced approach to fire safety in built structures.<\/p>\n

Key attributes of any building enclosure\u2019s design is the long-term performance of materials and assemblies. The way in which the materials are integrated into a building\u2019s envelope is critical to its overall performance including fire safety. Within a fire-resistive assembly, standards do not rely on individual component fire tests because materials can behave differently when combined and exposed to fire.<\/p>\n

Building code overview<\/strong><\/p>\n

\"This<\/a>
This flowchart can help building designers determine if an exterior wall assembly requires compliance with the National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components<\/em>, as determined by the International Building Code<\/em> (IBC<\/em>).<\/span>
Image courtesy DuPont Building Innovations<\/span><\/em><\/figcaption><\/figure>\n

The International Code Council (ICC) describes building codes as \u201ca jurisdiction\u2019s official statement on building safety. They are a set of minimum standards to ensure the health, safety, and welfare of the people. Codes address all aspects of building construction\u2014fire, life safety, structural, plumbing, electrical, and mechanical. The regulation of building construction can be traced through history for more than 4000 years. Through time, people have become increasingly aware of ways to make buildings safer for occupants and avoid catastrophic consequences of building-construction failures.\u201d<\/p>\n

The construction codes and standards used today were built on the experiences and lessons learned from large fires and other failures that resulted in significant losses of life and property. With over a 100 years of diligent work and thousands of contributing members, more than 300 codes and standards have been developed through the research, training, outreach, education, and advocacy efforts of groups, including the National Fire Protection Association (NFPA) and other global bodies like the Underwriter\u2019s Laboratories (UL) and Factory Mutual (FM).<\/p>\n

In the United States, the International Building Code<\/em> (IBC<\/em>) is the most widely adopted model code. Developed by ICC, IBC<\/em> is reviewed through a consensus development process every three years. IBC<\/em>, together with the International Energy Conservation Code<\/em> (IECC<\/em>), outline the minimum requirements for various building systems, including exterior wall systems incorporating energy-efficient materials like polyisocyanurate (ISO) insulation. The International Existing Building Code<\/em> (IEBC<\/em>) is often adopted by jurisdictions to further regulate alterations or other modifications made to existing buildings.<\/p>\n

These standards evolve over time to reflect new information that becomes available and as new products, research, and practices are developed and tested. In recent years, efforts to improve energy efficiency and reduce thermal bridging in exterior wall assemblies through the use of continuous insulation (ci) have increased the installation of ISO insulation or other products. To ensure fire safety is maintained in our pursuit of greater energy efficiency, the industry tests these exterior wall assemblies to rigorous fire performance standards.<\/p>\n

\"Figure<\/a>
Figure 1:<\/strong> Images illustrate the burner placements for the NFPA 285 test apparatus. Note the room burner is located inside the first floor of the test apparatus.<\/span>
Images courtesy Jensen Hughes<\/span><\/em><\/figcaption><\/figure>\n

IBC<\/em> Chapters 14 and 26<\/strong><\/p>\n

IBC<\/em> 2018 requires exterior walls on buildings of Construction Types I-IV to comprise tested and evaluated assemblies. The specific requirements for assemblies or materials will be determined by Chapters 14 and 26. Within both sections of the code, fire testing of assemblies in accordance with NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components<\/em>, is required under certain conditions.<\/p>\n

As a general rule, according to 2018 IBC<\/em>, exterior walls of any height on buildings of Construction Types I-IV containing foam plastic insulation \u201cshall be tested in accordance with and comply with the acceptance criteria of NFPA 285\u201d (Section 2603.5.5). It should be noted NFPA 285 is an assembly and not a material test. Therefore, approval is dependent on all components of the exterior wall assembly.<\/p>\n

Under Chapter 26 of 2018 IBC<\/em>, other performance requirements for foam plastic insulation apply when products are used in certain exterior walls. For example, foam plastic insulation products must have a flame spread index of 25 or less, and a smoke-developed index of 450 or less (Class A as tested per ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials<\/em>, or UL 723, Standard for Test for Surface Burning Characteristics of Building Materials<\/em>). Industry professionals should be familiar with the complete requirements of Section 2603.5 of 2018 IBC<\/em> when specifying and installing foam plastic insulation in exterior walls of commercial buildings.<\/p>\n

Additionally, Chapter 14 includes requirements for exterior walls that are constructed with other combustible components such as metal composite materials (MCMs) and exterior insulation finish systems (EIFS). The general rule for the use of foam plastic insulation still applies when used with various exterior wall coverings\u2014exterior walls of any height for Construction Types I-IV that contain foam plastic insulation must be tested and comply with NFPA 285.<\/p>\n

Details on NFPA 285<\/strong><\/p>\n

NFPA 285 provides a method for determining the flammability characteristics of exterior wall assemblies that are constructed with combustible components ranging from insulation and wall coverings to water-resistive barriers (WRBs). Developed from research initiated in the late 1970s and originally adopted as part of the Uniform Building Code<\/em> (UBC<\/em>) in 1988, NFPA 285 has been a keystone of building fire safety for many decades. The 2000 version of IBC<\/em> was the first ICC-published code to incorporate NFPA 285, and the requirements have been expanded over subsequent versions to include additional assembly configurations.<\/p>\n\n\n\n\n
POLYISOCYANURATE INSULATION PERFORMANCE<\/strong><\/span><\/td>\n<\/tr>\n
Polyisocyanurate (ISO) insulation is a closed-cell, rigid foam board consisting of a foam core sandwiched between two facers. When used as a continuous insulation (ci) on exterior walls, ISO can function both as a high-R, energy-efficient insulation solution\u2014creating a thermal barrier that reduces thermal bridges\u2014and as an environmental barrier to protect the building from air and water intrusion. ISO is widely known for its high R-value per inch compared to other insulation options, and is installed on the exterior side of the building\u2019s structure or frame and covered by an exterior finish. Many building professionals may be familiar with ISO\u2019s reputation as an insulation material for commercial roofing that delivers excellent thermal and fire performance.<\/p>\n

All construction materials, including ISO insulation, must provide a suitable margin of fire safety. ISO insulation possesses a high level of inherent fire resistance when compared to other foam plastic insulations due to its unique structure of strong isocyanurate chemical bonds. These bonds result in improved resistance to high temperature exposure as well as enhanced fire resistance. Additionally, ISO does not melt or drip when exposed to flame because it is a thermoset material. ISO forms a protective surface char when exposed to a sufficient flame, which resists the propagation of fire across the material (flame spread). This physical property is exhibited in the ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials<\/em>, or \u201cSteiner Tunnel\u201d test where ISO insulation test specimens remain intact during the test\u2019s fire exposure. Additionally, ISO can pass the National Fire Protection Association (NFPA) 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components<\/em>, without exterior gypsum or added fire-stopping around the windows. ISO\u2019s fire performance may offer other advantages and flexibility desired by design professionals. Building professionals should verify with the manufacturer the installation guidelines applicable to the specific material and assembly.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/p>\n

\"Timeline<\/a>
Timeline illustrates the evolution of the NFPA 285 standard from the 1970s to present.<\/span>
Image courtesy DuPont Building Innovations<\/span><\/em><\/figcaption><\/figure>\n

NFPA 285 provides a method for evaluating fire propagation of exterior wall assemblies for post-flashover fires of interior origin. The specific characteristics evaluated include the ability of the wall assembly to resist vertical and lateral flame propagation over the interior and the exterior surfaces and the cavity of the assembly and resistance to vertical flame propagation within the combustible components (NFPA 285, 2019). To achieve this, the method uses a full-scale, two-story (two room) test facility with a movable frame (Figure 1). The two-story wall assembly that will undergo testing is constructed on the test frame and moved and mounted onto the test apparatus. As required by the standard, the test assembly includes a specifically sized window opening. Two gas burners are used to sustain fire. One is placed inside the first-story test room (test room burner), and the window gas burner is fixed outboard of the wall opening.<\/p>\n

The primary performance characteristics evaluated by NFPA 285 are the capability of the entire test wall assembly to resist the following:<\/p>\n