Metal buildings are a popular choice for a variety of low-rise commercial and industrial applications; they are durable and relatively inexpensive to construct; they offer design flexibility and versatility; and steel is inherently fire-resistant. However, any structure can experience a fire, which means it’s critical that contractors use building materials that contain certified fire safety properties. A specific building material – insulation – takes center stage in the discussion about fire safety and metal buildings, as it is a major element of the building envelope and can either ignite or help stop the spread of a fire. Keep reading for a breakdown of the important fire safety factors to consider when choosing metal building insulation.  

Why Do Metal Buildings Need Insulation?

Not all metal buildings need insulation. Structures such as simple metal garages, barns and storage sheds often do not require insulation. Determining whether a metal building needs insulation should include a variety of factors, such as the location and climate of your project, as well as the end-use of the building.

Because metal is a strong conductor of heat, the majority of metal buildings in the U.S. are insulated. Hot and cold air easily enter and escape metal buildings, which means insulation is crucial in maintaining a comfortable indoor temperature in hot and cold climates. Additionally, insulation protects metal buildings from condensation, which occurs when warmer air comes in contact with cold surfaces, such as framing members and windows, or the colder region within the building envelope if moisture has penetrated the vapor retarder. A typical metal building insulation application also improves energy efficiency, reduces noise transfer, and provides a finished interior appearance.

What Type of Insulation Is Best for Metal Buildings?

It is critical that contractors use building materials that contain certified fire safety properties. Metal building insulation plays a vital role in enhancing fire safety measures, but the term “metal building insulation” encompasses a variety of materials. The most common types of metal building insulation include:

• Fiberglass
• Rigid board
• Insulated metal panels
• Mineral wool

Each insulation type contains its own fire safety profile and performs differently when exposed to fire. Some insulation materials, such as fiberglass and mineral wool, are non-combustible and, as standalone products, should not contribute to the spread of fire. Other insulation materials, such as foam plastic, are combustible and can release toxic fumes when they burn.

Fiberglass is the most popular choice for metal building insulation, as it is easy to install, has a lower cost compared to other types of insulation, and provides maximum thermal performance. Additionally, today’s fiberglass products are healthier for the environment than in years past, such as EcoTouch® Certified R from Owens Corning, which is GREENGUARD Gold Certified and possesses an average recycled content of 65% .

What Is ASTM E84 (UL 723)?

When it comes to metal building insulation, surface burning characteristics are the top measure of fire safety performance. ASTM E84 /UL 723 (Canadian equivalent: CAN/ULC S102) is the standard test method for surface burning characteristics of building materials and assesses the relative burning behavior of a material in the event of a fire. 

The test method for what would become ASTM E84 was first introduced in the 1920s when UL engineer Albert J. Steiner developed a 25-foot long tunnel with a noncombustible top to evaluate whitewash coatings. Demand for regulatory testing of building materials increased in the 1940s when U.S. cities experienced a flurry of historical tragedies, such as the Boston Cocoanut Grove fire of 1942, which resulted in 490 deaths. The first edition of UL 723: Test for Surface Burning Characteristics of Building Materials was published in 1950, which ASTM adopted and published in 1961. Today, UL 723 and ASTM E84 are technically equivalent and coexist throughout national fire codes. The Steiner Tunnel test is still the basis of testing for both standards.

Test results are measured by Flame Spread Index and Smoke Developed Index. In order for a product to comply with both ASTM E84 and UL723, it must have a Flame Spread Index no greater than 25 and a Smoke Developed Index no greater than 50. Today’s codes use these indices to classify various insulation products. 

The International Building Code (IBC) groups products into 3 classes, depending on their index values. Section 803.1.1 states that interior wall and ceiling finish materials shall be classified in accordance with ASTM E84 (UL 723) and categorized as follows:

• Class A = Flame spread index 0–25, smoke developed index 0–450;
• Class B = Flame spread index 26–75, smoke developed index 0–450; and
• Class C = Flame spread index 76–200, smoke developed index 0–450.

Fiberglass metal building insulation systems, both unfaced and laminated, should be Class A.

Are ASTM E84-Compliant Products UL-Rated?

An important distinction should be made regarding products that comply with ASTM E84 and those that are UL-rated. Products that pass UL 723 also pass ASTM E84; however, products that pass ASTM E84 are not automatically considered UL-rated. For a product to be labeled as UL-rated, it must be tested by Underwriters Laboratory and pass the requirements of UL 723. 

Faced vs. Unfaced Fiberglass Insulation

Faced Insulation

Traditional fiberglass metal building insulation applications include a low-permeance vapor retarder, or facing, adhered to fiberglass. The vapor retarder is typically exposed to the interior of the building, thereby creating a finished appearance. The role of a high-quality vapor retarder should not be underestimated: This is the building envelope’s top line of defense in preventing condensation. Vapor retarders are used to inhibit the passage of warmer moist air into the building envelope and are rated by the amount of moisture that can pass through them. The lower this rating, called a permeance rating, or “perm rating” for short, the less vapor transmission will occur and the more effective the vapor retarder will be. Additionally, vapor retarders protect insulation from physical abuse, and are often designed with flame-retardant chemistry to meet today’s fire codes and standards. 

The fiberglass, adhesive, and vapor retarder are each tested separately by the respective manufacturer and ascribed a Flame Spread Index and a Smoke Developed Index. As an added layer of insurance, some metal building insulation laminators will take it a step further and submit the complete assembly for testing, which ensures the final laminated insulation product – the vapor retarder laminated to the fiberglass – complies with UL 723. In order to be UL-rated, manufacturers and laminators participate in routine Underwriters Laboratory testing to ensure products are manufactured to consistently match the same parameters of the original product that was tested and complies with requirements. UL-rated products receive a classification mark, which is printed on the product label or product data sheet.

Assembly testing has gained wider popularity in recent years due to the desire for a more realistic reaction of how a building and its assemblies will respond to a fire. NFPA 286 is the Standard Methods of Fire Tests for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth. While ASTM E84 is the test method for surface burning characteristics of individual materials, NFPA 286 tests the overall assembly, which includes roof and wall panels, framing members, and applicable insulation system installed.

Unfaced Insulation

Evolving energy code requirements call for more insulation in metal buildings than ever before. In order to meet those requirements, metal building insulation laminators have created and patented high-R-value systems that meet prescribed energy code U-values. High-R-value insulation systems, called “ high-R systems ” for short, consist of two layers of fiberglass. Some systems contain two layers of unfaced fiberglass, while others include a faced layer and an unfaced layer. As a standalone component, unfaced fiberglass is classified as inherently non-combustible and can serve as a barrier within the building envelope to slow the spread of flames. Fiberglass manufacturers participate in third-party testing to ensure compliance with ASTM E84.

The NAIMA 202® Certified Fiberglass Metal Building Insulation Standard ensures that contractors receive a UL-rated product that meets a variety of additional standards related to fungi resistance, thickness, and other product attributes. Fiberglass that is NAIMA 202® Certified is ink-jetted with the manufacturer and or/product name, “NAIMA 202®” with a registered trademark symbol, and the appropriate R-value. Non-NAIMA 202 Certified fiberglass may not be UL-rated and contractors should ask for proof of testing from the metal building insulation supplier.

Find Fiberglass Insulation for Metal Buildings at Specialty Products and Insulation

Check for the “UL-Rated” classification mark on all final products to ensure it has been tested and is UL-rated.