Fire test tefinitions




Polyiso Insulation: The Product of Choice

The Importance of Building Codes in Construction

The fire performance of building products has always come under close scrutiny--; and for good reason. We want the structures that we live in and work in to be safe. It is for this reason that building codes exist, to provide a means to safeguard life and protect the private and public welfare through regulating the design, construction practices, construction material quality, location, occupancy and maintenance of buildings and structures. When regulating materials, many of the model building codes refer to performance standards developed by standard development organizations such as the American Society for Testing and Materials (ASTM). Some building codes and insurance rating organizations also rely on test information from Factory Mutual Research Corporation (FMRC) and Underwriters Laboratories Inc. (UL).

This technical bulletin discusses fire test procedures and applicability of these fire tests to building applications.For further information regarding these tests please consult ASTM, building code authorities or accredited testing laboratories.


The Importance of Building Codes in Construction

ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials, is a standard method to assess the spread of flame on the surface of a material. Often referred to as the " Tunnel Test," E84 involves installing a sample of material 20 inches wide and 25 feet long as the ceiling of a horizontal test chamber. The material is exposed to a gas flame on one end of the tunnel for a period of 10 minutes. The rate of flame front progression on the material is compared to selected standards and calculations made to produce a flame spread rating. Smoke from the fire in the tunnel is measured in the exhaust stack via a light beam to establish smoke developed ratings. ASTM E84 also has a number of other designations, such as UL 723, NFPA 255, or UBC 8-1.

Since ASTM E84 is a standard laboratory fire test on a single material, numerical ratings derived from E84 are not intended to reflect hazards presented by the test material under actual fire conditions.


Polyiso insulation, a thermoset material, stays intact during the fire exposure in the ASTM E84 test. Polyiso insulation successfully performs by forming a protective char layer and remaining in place during the tunnel test, meeting the necessary ratings dictated by building codes.

Thermoplastic materials, such as polystyrene, perform much differently in the tunnel test. Because the material softens at 165°F and melts at 200°F to 210°F, polystyrene melts ahead of the fire front and drips to the floor of the tunnel where it can continue to burn and spread the fire.

Although many polystyrene insulations claim a Flame Spread of 5, an examination of a testing laboratory certification label


(1) for an extruded polystyrene insulation reveals: 



 ASTM E119, Standard Test Method for Fire Tests of Building Construction and Materials, is used to determine the fire resistance of a complete assembly. For example, a wall system fire rating is measured by constructing a 10 foot by 10 foot section of a total wall system: framing, cavity insulation, sheathing, siding, gypsum wall board, etc. The wall section is installed vertically on a gas furnace, and the wall is exposed to a standard temperature curve for the time period for which a rating is desired, i.e., one, two, three, or four hours. Failure points during time of fire exposure are:

• Flame penetration through the wall section;

• An unacceptable temperature increase on the unexposed side of the assembly;

• Structural failure or collapse of the assembly.

Therefore, a one hour fire resistance rating is taken to mean that a structure incorporating the tested wall construction will not collapse, nor transmit flame or a high temperature, while supporting a design load, for at least one hour after a fully developed building fire. Roof/Ceiling and Floor/Ceiling constructions can also be tested horizontally in accordance with ASTM E119. The building code authorities usually designate the duration of fire resistance needed in a building. Factors affecting the duration resistance include type of construction, occupancy designations, location of the building and insurance criteria.

ASTM E 119 is also known as UL 263, NFPA 251, and UBC 7-1.

Fire Tests For Roof Systems

These tests measure:

• Resistance of a roof system to external fire exposure;

• Roof/Ceiling resistance to an internal fire exposure;

• Resistance to interior fire spread;

• A roof assembly fuel contribution rate.

Many of these tests involve testing the entire roof assembly, while some focus on the individual components.

Factory Mutual Roof Tests: FM Calorimeter (FM 4450/4470) and ASTM E108

Factory Mutual Research, established to assess product or material risk and system performance for specific insurance underwriters of property, liability and casualty policies, approves roof assemblies based upon a comprehensive series of tests outlined in FM Standards 4450 and 4470. This series of tests evaluates materials for their ability to resist fire, wind, hail, durability and corrosion of metal parts. Roofing assemblies that successfully pass all tests in Standard 4450 are given an FM Class 1 rating. Other assemblies are rated Class 2. FM classifies roof decks into two categories:

• Noncombustible Rated and

• Class 1 Rated. 

Noncombustible Rated decks are cementitious decks such as structural concrete, fiber reinforced cement, gypsum and certain lightweight insulating concretes. Class 1 Rated Decks may be steel, fire-retardant-treated wood, cementitious wood fiber, fiber reinforced plastic and certain lightweight insulating concretes. FM fire performance tests are the FM Calorimeter (FM Standard 4450/4470), used to assess the fuel contribution rate of a roof assembly and the Exterior combustibility test, conducted in accordance with ASTM E108. Insulation products are evaluated in roof assemblies for fire performance using the FM Calorimeter, which in turn qualifies them to be included in assemblies meeting FM 4450/4470 standards.

Exterior Combustibility is determined in accordance with ASTM E108 and involves all components of the roof assembly to be tested together. The test includes three parts:

• Spread of flame

• Intermittent flame

• Burning brand.

The spread of flame is the only test conducted on roof assemblies with concrete, steel or gypsum decks, while all three tests are performed on assemblies incorporating combustible (wood, plank, plywood, T&G; plank) roof decks. The slope of the roof and maximum insulation thickness are both factors as well. 

Underwriters Laboratories Inc. Roof Tests: UL 790, ANSI/UL 1256 and UL 263


 Underwriters Laboratories Inc. (UL) is an independent testing organization established to evaluate products for public safety. UL conducts three basic fire tests for roofing assemblies: Roof resistance to External Fire Exposure (UL Standard 790, ASTM E108, or UBC 15-2), Resistance to Interior Fire Spread, (ANSI/UL 1256), and Roof/Ceiling Fire Resistance Rating (UL 263, ASTM E119, NFPA 251 or UBC 7-1).

The UL version of ASTM E108 is previously described UL 790. As such, three test procedures are included in UL 790: Spread of Flame, Intermittent Flame and the Burning Brand. Since this test evaluates the performance of a roof assembly, all components of the roof system are tested together. With ANSI/UL 1256, the entire roof assembly including deck, adhesives, vapor retarders, insulation and roof membrane is tested in a 25 foot long tunnel for 30 minutes. The test uses an open flame with prescribed airflow in the tunnel. Ratings derived from the test are  eported in the UL Roofing Materials and Systems Directory under the Roof Deck Constructions category (TGKX).


The UL version of ASTM E119 is UL 263 and is used to determine the fire resistance of a complete assembly.


Importance of FM 4450 Calorimeter Test and ANSI/UL 1256 Resistance to Interior Fire Spread Test 

The spread of fire on the underside of a roof deck is a concern when buildings have large, open interior space, such as a warehouse or manufacturing facility. The two fire tests used by code bodies to evaluate the spread of fire in this manner are FM 4450, also called the FM Calorimeter Test and ANSI/UL 1256 also known as the Resistance to Interior Fire Spread Test. While both tests evaluate the entire roof assembly from deck to roof covering, the test conditions and test pass criteria are very different:


The White House Test

The "White House Test" was developed by Factory Mutual in the early 1950s as a means to investigate the reason for why the roof system contributed to the total loss of the GM factory in Livonia, Michigan. The test consisted of a non-combustible building 100' long, 20' wide, and 10' high with gasoline fired burners at one end and the other end open. Various roof systems were installed and the test ran for 30 minutes. Satisfactory performance was achieved, flaming on the underside of the deck limited to about 70', in one of a series of tests conducted in 1954 and 1955. The data from that series of tests was used by FM to develop the smaller scale FM 4450 Construction Materials Calorimeter. FM 4450 is now used by FM as the primary test for evaluating the combustibility of insulated roof systems installed on steel roof decks. FM no longer conducts White House tests.

FM 4880 25' High Full Scale Corner Test.

Not all roof deck systems are easily configured to be evaluated using FM 4450. About 10 years after use of the FM 4450 Calorimeter Test was started, Factory Mutual developed the FM 4880 25' High Full Scale Corner Test. This versatile full scale test is used to evaluate the flame spread potential of insulated roofs, roof panel systems, insulated walls and wall panel systems alone or in combination. The system(s) to be evaluated are installed on a corner structure 25' high with walls extending 38' and 50' from the corner. The fire exposure is 750 pounds of

wood pallets stacked in the corner 1' from the walls and is allowed to burn for the 15 minutes duration of the test. To pass the test no fire can exit the limits of the structure--beyond the 38' or the 50' walls--during the 15 minute test while the pallet fire naturally develops. This test is accepted by various code bodies and insurance rating organizations and can be used by FM in lieu of FM 4450 tests. 

Testing Laboratories

The testing and evaluating of polyiso insulation to show conformance with building code requirements is conducted by several nationally recognized laboratories:

• Intertek Testing Services

• Factory Mutual Research Corporation

• Omega Point Laboratories

• Warnock Hersey Laboratories

• Southwest Research Institute

• Underwriters Laboratories Inc.

• SGS United States Testing Co., Inc.


FOOTNOTE 1: Underwriters Laboratories Inc. Classification Certificate D-369 for Styrofoam Brand Insulation

manufactured by Dow Chemical U.S.A

FOOTNOTE 2: 1998 FMRC Building Materials Approval Guide p.3


The Polyisocyanurate Insulation Manufacturers Association (PIMA) produces technical bulletins in an effort to address frequently asked questions about polyiso insulation. PIMA's technical bulletins are published to help expand the knowledge of specifiers and contractors and to build consensus on the performance characteristics of polyiso. Individual companies should be consulted for specifics about their respective products.


The Polyisocyanurate Insulation Manufacturers Association (PIMA) is the North American trade association that advances the use of polyisocyanurate (polyiso) insulation. Polyiso is one of the nation's most widely used and cost-effective insulation products available.


PIMA's membership consists of manufacturers of polyiso insulation and suppliers to the industry. Our members account for a majority of all of the polyiso produced in North America.



Copyright © 2004 • All Rights Reserved.

The Polyisocyanurate Insulation Manufacturers Association

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