Surface-Burning Characteristics of Insulation for Metal Buildings
The January 2019 issue of Insulation Outlook featured an article by Dwayne Sloan titled “A Focus on Insulation Surface-Burning Characteristics.” Mr. Sloan is Director of Principal Engineers and Regulatory Services for the Building and Life Safety Technologies Division at Underwriters Laboratories (UL), and in his article, he referenced model codes and installation standards for insulation products. Now, we will take a deeper dive into those codes, regulations, and requirements as they pertain to insulation for metal buildings.
Recap of Why We Have ASTM E84 (UL 723)
The ancient Greek philosopher Plato, in the dialogue Republic, coined the phrase necessity is the mother of invention.
More than 70 years ago, within a relatively short period of time, the United States experienced 3 tragic fires:
- • November 1942, Cocoanut Grove Nightclub in Boston, Massachusetts—492 deaths;
- June 1946, La Salle Hotel in Chicago, Illinois—61 deaths; and
- December 1946, Winecroft Hotel in Atlanta, Georgia—127 deaths.
The common theme in each of these fires was the rapid flame progression
along the surfaces of the interior finish products. As a result, the necessity for a test method arose, and ASTM E84 (UL 723), a test for determining the surface burning characteristics of interior finish building materials, was invented.
Building Codes and Metal Building Insulation
ASTM E84 (UL 723) is the standard test referenced in all codes regarding the surface burning characteristics of insulation products. The result of the test yields 2 indices: a flame spread index and a smoke developed index. Code and standard bodies now use these indices to classify various insulation products.
The International Building Code (IBC) groups products into 3 classes, depending on their index values. Chapter 8 Interior Finishes, 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.
Armed with this knowledge, the next obvious question is: How does this affect the insulation products and systems used in the construction of a metal building?
First, let’s look at where fiber glass insulation is used.
Within a metal building, fiber glass insulation is most commonly used in the walls and ceilings, and is exposed to the interior of the building. Fiber glass insulation also can be found in concealed spaces and in plenum applications. For example, insulation is sometimes left exposed within an enclosed cavity of a metal building, which serves as the return air plenum for the HVAC system.
Now that we know where it is used, what codes do we need to understand regarding the surface-burning characteristics of the insulation being used?
Let’s first address plenum applications. The following codes have specific requirements regarding this:
- International Mechanical Code,
- Uniform Mechanical Code, and
- National Fire Protection Agency (NFPA 90A).
All state that any insulation material exposed within a plenum must have:
- Flame spread < 25, and
- Smoke-developed < 50.
Next, we have insulating materials in concealed spaces. This is addressed by the IBC, Section 720.2, stating that the insulation must be Class A. That is:
- Flame spread < 25, and
- Smoke-developed < 450.
Lastly, the most common use of insulation in a metal building is for walls and ceilings, where it is exposed. IBC Section 720.3 requires all exposed
insulating materials be Class A. That is:
- Flame spread < 25, and
- Smoke-developed < 450.
When it comes to insulating metal building ceilings and walls, there are several system options. Per ASHRAE 90.1-2019, insulation systems can be single layer, double layer, liner system, or filled cavity. In each of these systems, the insulation can be either faced (laminated) or unfaced.
In general, with fiber glass insulation systems in a metal building, there are 3 types of building materials that need to be Class A: unfaced metal building insulation, vapor retarder facings, and faced metal building insulation.
Common Misconceptions Regarding Faced Metal Building Insulation
What everyone should understand is that there is a significant difference between ASTM E84 (UL 723) testing on individual materials compared to
Faced or laminated metal building insulation that will be exposed to the interior of the structure must be Class A. Therefore, the faced or laminated product is a composite material and must be tested as such. What does that mean? Laminated metal building insulation is composed of fiber glass blanket, a vapor retarder facing, and some type of adhesive. However, if the unfaced insulation has been tested and is Class A, and the vapor retarder facing has been tested and is Class A, and the adhesive has been tested and is Class A, it DOES NOT mean that the faced metal building insulation is Class A.
The true surface burning characteristic of faced metal building insulation can only be known by testing the material when all components are together, as a finished product.
How Do I Know if the Faced Metal Building Insulation I Am Using Is Class A?
The surface burning characteristics index rating is on the product label and can be on the product specification data sheet. Nationally Recognized Testing Laboratories are recognized by OSHA and can be hired by manufacturers to ensure that products comply with the ASTM E84 (UL 723) requirements. Many of them offer certification programs which means that a product has been tested, is manufactured to consistently match the same parameters of the original product that was tested, and complies with requirements. As an added assurance, the manufacturing facility keeps records of all production and is routinely visited and evaluated by the third party. As a result of satisfactory testing, a classification mark is printed on the product data sheet or product label, as shown in Figure 1. “FHC 25/50” on this label refers to Fire Hazard Classification, with 25 being the flame spread index and 50 being the smoke developed index. A product labeled with the FHC rating of 25/50 would be Class A material.
The vast majority of fiber glass insulation systems in metal buildings should be Class A material to comply with building codes. The only way to be certain that the materials being used will meet building codes is if the surface burning characteristics index rating is certified and shown on the product label or specification data sheet.
This article was published in the June 2020 issue of Insulation Outlook magazine. Copyright © 2020 National Insulation Association. All rights reserved. The contents of this website and Insulation Outlook magazine may not be reproduced in any means, in whole or in part, without the prior written permission of the publisher and NIA. Any unauthorized duplication is strictly prohibited and would violate NIA’s copyright and may violate other copyright agreements that NIA has with authors and partners. Contact firstname.lastname@example.org to reprint or reproduce this content.