Liner Specifications and Standards

The choice of lining material for any air-distribution system is an important consideration for the specifying engineer. There are many options available and each material has a potential impact on project cost and thermal/acoustical performance. While the traditional lining materials in the industry have been fiberglass-based, there are other alternatives available today. These new materials have many advantages from the standpoint of physical properties as well as cost and performance. In order to successfully promote these new materials, it is helpful to have a better understanding of current industry standards and how they are applied.

There are several agencies that set standards for ductwork and equipment-lining materials. They include the American Society for Testing and Materials International (ASTM), National Fire Protection Association (NFPA) and Underwriters Laboratories Inc. (UL). While most of the standards they publish must be purchased and can be costly to acquire, it is often not necessary to know more than the title of the standard when determining whether a material is in compliance. Here are some of the most frequently referenced standards:

• ASTM C411 - Standard Test Method for Hot-Surface Performance of High-Temperature Thermal Insulation

• ASTM C518 - Standard Test Method for Steady-State Thermal Transmission Properties by Means of Heat Flow-Meter Apparatus

• ASTM C665 - Standard Specification for Mineral-Fiber Blanket Thermal Insulation for Light Frame Construction and Manufactured Housing

• ASTM C739 - Standard Specification for Cellulosic Fiber Loose-Fill Insulation

• ASTM C1071 - Standard Specification for Fibrous Glass Duct-Lining Insulation (Thermal and Sound-Absorbing Material)

• ASTM C1104 - Standard Test Method for Determining the Water Vapor Sorption of Unfaced Mineral-Fiber Insulation

• ASTM C1338 - Standard Test Method for Determining Fungi Resistance of Insulation Materials and Facings

• ASTM E84 - Standard Test Method for Surface-Burning Characteristics of Building Materials

• ASTM E96 - Standard Test Methods for Water-Vapor Transmission of Materials

• ASTM G21 - Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi

• ASTM G22 - Standard Practice for Determining Resistance of Plastics to Bacteria

• NFPA 90A - Standard for the Installation of Air-Conditioning and Ventilation Systems

• NFPA 90B - Standard for the Installation of Warm Air Heating and Air-Conditioning Systems

• NFPA 225 - Standard Method of Test of Surface-Burning Characteristics of Building Materials

• UL 181 - Standard for Factory-Made Air Ducts and Air Connectors

• UL 723 – Standard for Test for Surface-Burning Characteristics of Building Materials

These standards are commonly referenced in equipment specifications, and most of them only cause confusion. The first thing to note is that each of these standards is either a test method or specification. Test methods define a procedure for measuring a physical property associated with a material. These procedures are often material specific. Specifications (often simply entitled “Standard”) generally reference several acceptable test methods and set maximum or minimum limitations on the result of a test for compliance.

In order to determine compliance with a specification requirement, it is important to note whether the referenced standard is an actual specification or just a method of test. Since there is no way to comply with a test standard, the inclusion of test standards in a specification often causes confusion for vendors. Another common problem involves specification that describe a specific lining material, but reference standards that do not apply to that specific material. All of these issues can be identified and clarified by simply knowing the full titles of the referenced standards.

In addition to the aforementioned ASTM, NFPA and UL standards, there are additional industry standards published by the Air-Conditioning, Heating and Refrigeration Institute (AHRI), American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and U.S. Green Building Council (USGBC). Traditionally, ASHRAE publishes test standards for equipment and guidelines for environmental conditions such as ventilation, indoor-air quality and thermal comfort. AHRI concentrates mainly on equipment ratings and performance certification. USGBC publishes the Leadership in Energy and Environmental Design (LEED) standard.

Since most new construction projects will be designed with a goal toward achieving LEED certification, it is important to know what the USGBC requirements are for ductwork and equipment linings. According to the latest LEED 2009 standard, in order to achieve Indoor Environmental Quality (IEQ) Prerequisite 1, the building design must meet the minimum requirements of Sections 4 through 7 of ASHRAE Standard 62.1-2007 Ventilation for Acceptable Indoor-Air Quality. Under Section 5 ‘Systems and Equipment,’ it states that all airstream surfaces (with the exception of sheet metal surfaces and metal fasteners) shall be determined to be resistant to mold growth in accordance with a standardized test method such as those found in UL 181 or ASTM C1338. In addition, all airstream surfaces (with the exception of sheet metal surfaces and metal fasteners) shall be determined to be resistant to air erosion in accordance with the test method described in UL 181. In other words, any lining material that can meet the requirements of UL 181 is acceptable for use in any LEED-certified building.

Here are some typical questions about liner specifications and standards:

Does that mean I can put exposed dual-density fiberglass in a LEED Platinum building?

Yes, it does. However, it may not be the best choice. Many engineers are looking for alternatives to fiberglass because no one knows how that material may be treated in the future. Today, there are innovative new lining materials that can provide improved indoor-air quality with little if any increase in cost.  

What kind of ‘new liners’ are you talking about?

Titus has seized the initiative to eliminate fiberglass from many of our product lines. We currently offer our latest EcoShield liner in ½” or 1”-thickness with cloth-facing for the same price as fiberglass. This material is made from pre-consumer recycled natural cotton fibers chemically-treated to be fire-retardant and anti-microbial. The same material is also available with a scrim-reinforced foil-facing for critical environmental applications for a modest up-charge. We also offer our FibreFree liner in 3/8” or 1”-thickness. This material is called engineered polymer foam insulation (EPFI). It contains an anti-microbial agent throughout to fight mold growth and cannot absorb any moisture, making it ideal for humid climates and applications wherein moisture can cause problems.

I submitted EcoShield on a project recently, but was rejected by the engineer because I could not prove that this material meets ASTM C1071. Why does EcoShield not meet ASTM C1071?

EcoShield technically cannot meet ASTM C1071 because that standard only applies to fiberglass products. That does not mean that EcoShield is not suitable as a duct-lining material, because it may actually outperform fiberglass in the same tests. The engineer’s standard specification probably only takes into account fiberglass products and does not address the new liners available today. We suggest providing EcoShield submittal sheets, explaining the advantages and encouraging him to update his standard specification to include newer materials. So long as the lining materials meet UL 181, they should be acceptable.

With a better understanding of the industry standards, it should be easier to promote new and better lining materials to the engineering community.

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Chief Engineer Randy Zimmerman (rzimmerman@titus-hvac.com).