PLASTIC

Section 2603 Foam Plastic Insulation

Section 2604 Interior Finish and Trim

Section 2605 Plastic Veneer

Section 2606 Light-Transmitting Plastics

Section 2607 Light-Transmitting Plastic Wall Panels

Section 2608 Light-Transmitting Plastic Glazing

Section 2609 Light-Transmitting Plastic Roof Panels

Section 2610 Light-Transmitting Plastic Skylight Glazing

Key Points

Section 2603 Foam Plastic Insulation

During the early 1970s, the Federal Trade Commission (FTC) investigated claims made by some manufacturers in the plastics industry of “slow burning” or “nonburning” as related to foam plastic insulation materials. With assistance from the former National Bureau of Standards, now called the National Institute of Standards and Technology, the FTC concluded that these claims were erroneous because of improper testing. Because of the earlier criticisms aimed at the claims, the code changes that were finally adopted into the codes were, of necessity, somewhat conservative.

The provisions were developed by the Society of the Plastics Industry, Inc. (SPI), after numerous meetings, hearings, and seminars relating to the hazardous characteristics of the materials. During this time, SPI funded an extensive program of research that reviewed the then-current test procedures, with a goal of establishing new test procedures where necessary to properly reflect the hazards of the material as it would actually be used in buildings.

The code provisions developed as a result of the extensive research were centered on two basic concepts:

1.   An index limitation of the flame spread and smoke developed to 75 and 450, respectively.

2.   Separation of the foam plastic insulation from the interior of the building by an approved thermal barrier. The adequacy of the thermal barrier is related to the time during which the thermal barrier is expected to remain in place under fire conditions.

2603.2   Labeling and identification.   In addition to the flame-spread and smoke-developed criteria, the code also requires that the containers of foam plastic and foam plastic ingredients be labeled by an approved agency to show that the material is compliant. There are many foam plastic products on the market that do not comply with the code and that were not intended for use in construction. The labeling requirement is intended to prevent the misapplication of products not designed for this use.

2603.3   Surface-burning characteristics.   It is important that any foam plastic insulation or foam plastic core material found in manufactured assemblies be limited in flame spread and smoke development. In this section, the code limits such foam plastic materials to a flame-spread index of 75 and a smoke-developed index of 450 where tested at the maximum intended thickness of use. Various exceptions are provided for interior trim, cold-storage buildings and similar facilities, interior signs in covered mall buildings, listed roof assemblies, and special approvals.

2603.4   Thermal barrier.   Because of the potential hazards involved, foam plastic must typically be separated from the interior of a building by an approved thermal barrier. Gypsum wallboard at least ½ inch (12.7 mm) in thickness satisfies this requirement, as does any equivalent thermal barrier material complying with the criteria of this section. It must be demonstrated by approved testing that the thermal barrier will remain in place for the required 15-minute time period.

When the following conditions are met, the thermal barrier described above is not required; however, some form of protective membrane is typically mandated:

Masonry or concrete construction. See Figure 2603-1. When foam plastics are encapsulated within concrete or masonry walls, or floor or roof systems, the code does not require a thermal barrier as long as the foam plastic is covered by a minimum 1-inch (25-mm) thickness of the masonry or concrete.

Figure 2603-1   Encapsulated foam plastic.

Cooler and freezer walls. Cold storage uses provide a unique condition for foam plastic insulation in that thicknesses are generally required to be greater than 4 inches (102 mm) for proper thermal insulation, although 4 inches (102 mm) is about the maximum that can be tested. The code, in all other cases, places limits on the thickness of the foam plastic insulation to that which was tested. However, because of the nature of the use in cold-storage facilities, the ignition hazards are not great. Therefore, the code permits foam plastic insulation in greater thicknesses, up to a maximum of 10 inches (25 mm), even though tested in a thickness of 4 inches (102 mm). The intent is that the foam plastic will be provided with a complying protective thermal barrier. In the case of interior rooms within a building, the foam plastic is required to be protected on both sides with a complying thermal barrier.

Provisions are included to permit cooler and freezer walls without a thermal barrier, provided the foam plastic has a flame-spread rating of 25 or less, has minimum allowable flash and self-ignition temperatures of 600°F and 800°F (316°C and 427°C), respectively, and the foam is protected by 0.032-inch-thick (0.8-mm) aluminum or 0.0160-inch-thick (0.4-mm) steel. The cooler or freezer and the portion of the building where the cooler or freezer is located must be sprinklered in this case. Again, the code presumes that with a low-hazard use, such as a cold storage and freezer box, the metal covering will prevent the actual impingement of any flames on the foam plastic, and the sprinkler system will provide the cooling necessary to maintain proper low temperatures to prevent ignition of the foam plastic.

Walk-in coolers. Where freestanding coolers and freezers have an aggregate floor area not exceeding 400 square feet (37 m²), the code contains an exception that, in effect, provides for no thermal barrier and no sprinkler protection as long as the foam plastics comply with the general provisions of Section 2603.4.1.3. The foam plastic must be covered by an aluminum or steel facing of appropriate thickness. If the foam plastic material is over 4 inches (102 mm) in thickness, a complying thermal barrier must enclose the material.

Exterior walls—one-story buildings. For one-story buildings, metal-clad sandwich panels with foam plastic cores with thicknesses up to 4 inches (102 mm) are permitted to be installed without a thermal barrier, provided the metal cladding complies with the provisions outlined in Section 2603.4.1.4 and, furthermore, the building is protected with automatic fire sprinklers. In this case, the code assumes that the protection and cooling effect provided by automatic sprinklers is a reasonable alternative to the thermal barrier.

Roofing. This item covers two different cases involving roof coverings or roof assemblies:

1.   The first case involves nonclassified roof assemblies or roof coverings. As there are generally no test standards for these prescriptive assemblies, the code provides that they may be applied over foam plastic when the foam is separated from the interior of the building by minimum 0.47-inch (12-mm) wood structural-panel sheathing bonded with exterior glue. The edges of the wood structural-panel sheathing must be supported by blocking or be of tongue-and-groove construction or of any other approved type of edge support. In this case, the thermal barrier is waived, as well as the smoke-developed index.

Based on the fact that a wood structural panel provides an adequate separation for ordinary roof-covering assemblies, it is also considered acceptable for a tested assembly. Thus, it is the intent of the International Building Code® (IBC®) that any roof covering assembly installed over foam plastic may be installed with only a complying wood structural-panel separation between the assembly and the interior of the building. Where the wood structural-panel separation is utilized, it is important to recognize that the joints must be protected even though the roofing specimen used during the fire-retardancy test might have been installed over wood structural panels with abutted joints without any supplemental protection.

2.   The second case involves the use of Class A, B, or C roof-covering assemblies in which the foam plastic insulation is also considered to be an integral part of the assembly. See Figure 2603-2. Here, a nationally recognized test standard for insulated roof decks is to be utilized. The test standards for insulated roof-deck construction are adequately conservative so that assemblies passing either of the two test standards are considered to meet the intent of the code without any limit on flame spread or smoke development. Furthermore, no thermal barrier is required.

Figure 2603-2   Foam plastic used with roof covering.

It should be noted that most insulated metal decks that are listed require that the deck be nonperforated—essentially a nonacoustical deck. Acoustical decks are commonly proposed in gymnasiums and auditoriums for sound control purposes and would therefore require a thermal barrier unless specifically listed under UL 1256 or NFPA 276.

Attics and crawl spaces. See Figure 2603-3. This item describes specific methods used to protect foam plastics located within attics and crawl spaces (in lieu of a complying thermal barrier) where entry is provided only for service of utilities. The phrase “where entry is provided only for service of utilities” is intended to restrict these reduced requirements for a thermal barrier to those unused areas where there are no heat-producing appliances. In addition, drop lights or portable service lights are often utilized when serving equipment in such concealed spaces, and such lighting devices pose an ignition threat to the foam plastic. Thus, the reduced provisions are intended to provide a barrier whose only purpose is to prevent the direct impingement of flame on the foam plastic.

Figure 2603-3   Foam plastic in attic and crawl spaces.

The reduced level of protection is also applicable in those situations where the service of utilities is not an issue. If there are no utilities within the attic space or crawl space that require service, the minimum described degree of separation between the foam plastic and the enclosed space must still be provided where a complying thermal barrier is not installed. Where the attic or crawl space provides a suitable area that exists for a purpose other than the access to utilities, such as storage, a thermal barrier complying with Section 2603.4 is required.

Doors not required to have a fire-protection rating. Pivoted or side-hinged doors not required to have a fire protection rating are permitted to be installed without the thermal barrier, provided the door facings are of sheet metal of the thicknesses prescribed in this section. The rationale behind the waiver of the thermal barrier is that the foam plastic is completely encapsulated within the sheet-metal facings, and the quantity of foam plastic in protected doors is quite small.

Garage doors. Garage doors, other than those in garages accessory to dwellings, that contain foam plastic are allowed, provided the door does not require a fire-resistance rating and is faced with materials prescribed by this section. If the garage door containing the foam plastic does not have an aluminum, steel, or wood facing of the minimum thickness prescribed, the door must be tested in accordance with DASMA 107 Room Fire Test Standard for Garage Doors Using Foam Plastic Insulation. This provision is intended to regulate the commercial applications of overhead, sectional, and tilt-up types of doors.

Siding backer board. Where it is desired to insulate exterior walls under exterior siding, the code permits foam plastic to be used as a backer board for the siding, provided the insulation has a potential heat of not more than 2,000 Btu per square foot (22.7 mJ/m²). The thermal barrier is not required under these circumstances as long as the siding backer board has a minimum thickness of ½ inch (12.7 mm) and is separated from the interior of the building by not less than 2 inches (51 mm) of mineral-fiber insulation or the equivalent.

The code also permits the siding backer board without a thermal barrier when the siding is applied as re-siding over existing wall construction. This is reasonable considering the separation provided by the existing construction and limitations on the potential heat imposed by the code.

Type V construction. The use of spray-applied foam plastic has become common in wood-frame construction for the sill plates, joist headers, and rim joists. Such a limited amount of foam plastic insulation is considered acceptable without the protection afforded by a thermal barrier. Testing has been conducted to evaluate the behavior of foam plastic having the density, thickness, flame-spread, and smoke-developed indices stipulated. The results indicated no substantial performance difference between a foam plastic–insulated wood floor system and an all-wood floor system.

Floors. Section 2603.4.1.14 provides a viable means to protect foam plastic insulation when it is installed within a floor system. The thermal barrier required to separate foam plastic insulation installed beneath a walking surface must not only be an adequate barrier to protect the foam plastic, but also be durable enough to withstand the load and wear-and-tear that is needed for the floor. With society’s focus on energy efficiency and conservation, many new types of products are being used that incorporate foam plastic insulation for energy reasons. One example is the use of structural-insulated panels where the foam plastic is laminated between two structural wood facings. These types of panels are often used in floor systems.

Although a ½-inch (12.7-mm) wood structural panel (i.e., plywood or oriented strand board) is not by itself considered as a complying “thermal barrier” as required by Section 2603.4, it will fulfill the dual need for structural strength and thermal protection of the foam insulation. In the case of a floor, the use of such panels will provide sufficient protection because, in the event of an interior fire, the floor faces a reduced exposure and is typically the last building element to be significantly exposed by the fire. See Figure 2603-4.

Figure 2603-4   Floors with foam plastic insulation.

It is important to note that the protection provided by wood structural panels is only accepted on the walking surface side of the floor. If the floor is used in multistory construction, then the underside of the floor system (ceiling of the room below) must be covered by the typically required thermal barrier. The thermal barrier protection on the bottom side of the assembly does not get to take advantage of the reduction because it will not be used as a walking surface does, and it will face a more severe exposure to an interior fire.

The exception is intended to address items such as carpet padding, and others, that do not need to be covered by a thermal barrier.

2603.5   Exterior walls of buildings of any height.   The provisions for foam plastic insulation also allow such material in the exterior walls of buildings required to have noncombustible exterior wall construction (Types I, II, III, and IV). Applicable to such buildings of any height, an important provision of this section requires that the wall be tested in accordance with NFPA 285. This test provides a method of evaluating the wall’s flammability characteristics that are due to the combustible foam plastic materials within the wall. Wall assemblies need not be tested where they can comply with the provisions of Section 2603.4.1.4; however, this allowance is only applicable to fully sprinklered, one-story buildings. Section 2603.5.1 also requires that test data be provided to show that if a fire-resistance rating is required, the rating of the wall containing the foam maintains the required rating. Moreover, the foam plastic insulation must:

1.   Be separated from the interior of the building with a thermal barrier meeting the provisions of Section 2603.4.

2.   Not have a potential heat content exceeding that of the foam plastic insulation contained in the wall assembly as tested.

3.   Have a maximum flame-spread index of 25 and smoke-developed index of 450. Exterior coatings and facings, tested individually, must also comply with these flame-spread and smoke-development limitations.

4.   Be labeled by an approved agency.

5.   Comply with the ignition limitations imposed by Section 2603.5.7.

2603.6   Roofing.   As previously addressed, complying foam plastic insulation may be utilized as a portion of a roof-covering assembly, provided the assembly with the foam plastic insulation has been tested in accordance with ASTM E 108 or UL 790, and has been listed as a Class A, B, or C roofing assembly.

2603.9   Specific approval.   In this section, the code provides for those cases where foam plastic products and protective coverings do not comply with the specific requirements of Sections 2603.4 or 2603.6. The specific approvals are based on testing that is related to the actual end use of the products. The code refers to a number of test standards for determining specific approvals and, in addition, there are others that utilize some variation of the room test and are designed for testing exterior wall applications.

Section 2604 Interior Finish and Trim

The provisions of Chapter 8 for wall and ceiling finishes are applicable to those plastic materials installed as trim or interior finishes. In addition, foam plastics used as interior finish and trim must be in compliance with the provisions of this section, as well as the flame-spread index and smoke-developed index requirements of Chapter 8. By limiting the density, thickness, wall and ceiling area, as well as flame spread of foam plastic materials, the hazard level created by the exposure of foam plastics is low.

Section 2605 Plastic Veneer

Because it is a combustible material, plastic veneer used in the interior of a building is required by the code to comply with the interior finish requirements of Chapter 8.

Where plastic veneer is used on the exterior of a building, the code requires that the veneer be of approved plastic materials as defined in Section 202. This places severe restrictions on the combustibility and smoke development of the plastic materials. Because plastic materials are combustible, the code limits their attachment on any exterior wall to a height no greater than 50 feet (15,240 mm) above grade. Furthermore, the IBC limits the area of plastic veneer to 300 square feet (27.9 m²) in any one section and requires each section to be separated vertically by a minimum of 4 feet (1,219 mm). The 4-foot (1,219-mm) separation helps control the rapid vertical spread of fire. The code anticipates that local fire-fighting forces can effectively fight a fire that involves plastic veneer up to a height of about 50 feet (15,240 mm). Also, if the plastic veneer involves too large an area, it is conceivable that a fire could overtax local fire-fighting forces. The exception applies to Type VB buildings where the walls are not required to have a fire-resistance rating. In this case, the plastic materials do not present a greatly different hazard than the unprotected wood construction.

Plastic siding used on the exterior of a building is regulated separately from plastic veneer. The provisions of Section 2605 are not appropriate for exterior plastic siding, as the requirements for exterior wall coverings established in Sections 1404 and 1405 are to be applied.

Section 2606 Light-Transmitting Plastics

It is the intent of this section and Sections 2607 through 2611 to regulate the use of light-transmitting plastics—those plastics used in the building envelope or with interior lighting to transmit light to the interior of the building. Light-transmitting plastics are regulated because they are combustible materials. The unregulated use of combustible materials in the roof structure and for the exterior walls can possibly defeat the intent of the provisions of the code relating to types of construction. Thus, these six sections regulate these materials so that they do not materially affect the other requirements of the code regarding types of construction.

Any use of light-transmitting plastic materials must be approved by the building official and be based on technical data submitted to substantiate their use. As a basis of this approval, the building official should refer to Section 202 for the definition of “Plastic, approved.” The definition refers to the criteria of Section 2606.4 for the combustibility classifications of approved plastic materials, determined to be either Class CC1 or CC2 in accordance with ASTM D 635.

Materials of light-transmitting plastic, such as lenses, panels, grids, or baffles, located below independent light sources are thought of as creating a light-diffusing system. Light-diffusing systems are specifically regulated in Section 2606.7. Regulated as to occupancy, location, support, installation, and size, light-diffusing systems pose potential hazards that are due to their combustibility.

Section 2607 Light-Transmitting Plastic Wall Panels

Exterior wall panels are regulated for the same reason as plastic glazing in openings. However, because exterior wall panels are sheet materials, they generally constitute larger unbroken areas than plastic glazing for openings do; as a result, their burn-rate characteristics are more critical than those for plastic glazing in openings addressed in Section 2608.

Section 2608 Light-Transmitting Plastic Glazing

Because plastic glazing materials are combustible, their use is limited to openings not required to be fire protected. In the case of building construction other than Type VB, their use is further restricted. The glazing of openings not required to be fire protected in Type VB construction is essentially unlimited as to the area, height, percentage, and separation requirements applicable to the individual glazed openings.

For plastic-glazed openings in buildings other than Type VB, restrictions are placed on the area, height, percentage, and separation requirements for the individual glazed openings because plastic glazing materials are combustible. In other types of construction, unprotected combustible materials must be limited in accordance with their real extent and separation. Because of the combustibility of plastic glazing, the code requires flame barriers at each floor level for nonsprinklered multistory buildings to prevent the transmission of flame from one story to another by way of combustible openings.

As with other provisions of the code limiting the height of combustible materials above grade, this section also limits the height of plastic materials above grade to 75 feet (22,860 mm) unless the building is sprinklered throughout.

Section 2609 Light-Transmitting Plastic Roof Panels

Plastic panels are regulated on the basis of three conditions, of which only one needs to be met in order to utilize light-transmitting plastic panels in roofs of all occupancies other than Groups H, I-2, and I-3. Light-transmitting plastic roof panels may be installed in buildings equipped throughout with an automatic sprinkler system, in buildings where the roof construction is not required to have a fire-resistance rating, or where the roof panels meet the requirements for roof coverings in accordance with Chapter 15.

Because plastic roof panels constitute unprotected openings in the roof, the code requires that they be separated from each other by 4 feet (1,219 mm) horizontally. The minimum 4-foot (1,219-mm) separation is not mandated for fully sprinklered buildings, nor is it required in buildings housing low-hazard occupancies as limited by Exception 2 or 3 to Section 2609.4. Furthermore, their location on the roof is regulated based on the building’s location in respect to lot lines. Roof panels shall be located at least 6 feet (1,829 mm) from exterior walls that are located in a manner to require protected wall openings.

Because Class CC1 plastics have a slower burn rate than Class CC2 plastics, the code limits Class CC2 plastics to smaller areas than allowed for Class CC1 materials. The area limitations may be doubled based on the installation of a sprinkler system, whereas plastic roof panels in low-hazard occupancy buildings, greenhouses, and patio covers are not limited in area under specific conditions. As with exterior wall panels, the actual numbers relating to area, height, and separation requirements must be somewhat arbitrary but are reasonable code limits determined by a consensus of knowledgeable experts.

Section 2610 Light-Transmitting Plastic Skylight Glazing

In this section, the requirements for skylights are more detailed than those for roof panels in Section 2609 because there is no limit on the type of construction or fire-protection requirements for the roof assembly. Furthermore, skylights have unique requirements, such as those for flashing and resistance to burning brands. Also, as plastic-glazed skylights provide an unprotected combustible assembly in the roof, limitations must be placed on the area, percentage, and separation of each unit. Each unit’s location on the roof relative to lot lines is regulated in a manner consistent with that for plastic roof panels.

Two of the primary concerns of plastic-glazed skylights are related to flashing at the intersection with the roof and their ability to resist the effects of flying, burning brands. Therefore, with one exception, the code requires that they be mounted on a curb at least 4 inches (102 mm) above the plane of the roof so that proper flashing may be accomplished. The exception involves skylights on roofs that have a minimum slope of 3 units vertical in 12 units horizontal (25-percent slope) and applies only to Group R-3 occupancies and on buildings having unclassified roof coverings. This slope should provide adequate roof drainage to accommodate skylights. The slope requirements for flat or corrugated plastic-glazed skylights and the rise requirement for dome-shaped skylights are based on the skylights’ ability to shed flying brands. However, when the glazing material in the skylights can pass the Class B burning brands test specified in ASTM E 108 or UL 790, there is no limitation on slope, either of flat or corrugated glazed skylights, or on rise in the case of dome-shaped skylights.

The requirement for the protection of edges of plastic-glazed skylights or domes is to prevent the rapid spread of fire along the roof, as the edges of the plastic glazing material ignite more readily than the interior portions. Under those conditions where unclassified roof coverings are permitted, the metal or noncombustible edge material is not required.

As with roof panels, the various limitations on area, percentage, and separation of skylights are somewhat arbitrary and, as with roof panels, are based on a consensus among knowledgeable experts on what is reasonable.