Do Fibers Erode in the Airstream?

Article content provided by Johns Manville.

When it comes to HVAC systems, the durability and performance of duct liners are crucial. One of the key concerns is whether fibers erode in the air stream. To address this, ASTM C1071 sets stringent requirements for duct insulation materials.

ASTM C1071 Standards
ASTM C1071 requires that insulation be tested at 2.5 times the rated velocity in a typical duct section for 4 hours. During this test, the insulation must not break away, crack, peel, flake off, or show evidence of delamination or continued erosion when air is passed through typical duct sections including straight sections and an elbow. This ensures that the insulation can withstand high-velocity air streams without degrading.

Fiberglass Duct Liner Performance
Fiberglass duct liners, like Linacoustic RC® from Johns Manville, are UL tested to withstand air velocities of up to 15,000 feet per minute (fpm), which is equivalent to class 4 hurricane force winds. In comparison, typical HVAC systems operate at velocities ranging from 400 to 3,000 fpm. This demonstrates the robustness of fiberglass duct liners under extreme conditions.

Comparison of Insulation Types
Here’s a comparison of different insulation types based on their air erosion ratings:

Insulation Type	Air Erosion Rating (fpm)	Comparison to Fiberglass
Linacoustic RC®	15,000	Baseline
Elastomeric Duct Liner	10,000	50% lower
Polyester Fiber Duct Liner	10,000	50% lower

Fiberglass duct liners have the highest air erosion ratings among internal duct liners, making them 50% more resistant to air erosion compared to elastomeric or polyester fiber duct liners.

In conclusion, fiberglass duct liners offer superior performance in terms of air erosion resistance, making them an excellent choice for HVAC systems that require durable and reliable insulation. By meeting and exceeding ASTM C1071 standards, fiberglass duct liners, like Linacoustic RC ensure long-lasting performance even under extreme conditions.

Actions Designers and Specifiers Can Take Today

1. Request third-party ASTM E84 testing report for the specific products. The testing program found that, as a product category, elastomeric products with published flame spread index (FSI) and smoke developed index (SDI) values of 25 and 50 far exceeded claimed performance. While some products may meet 25 FSI and 50 SDI, the values included on product data sheets for elastomeric products were not in line with actual product performance. During engagement with manufacturers to discuss participation in the program, elastomeric manufacturers did not provide ASTM E84 test reports to corroborate their published data sheet claims for fire performance.
2. Revisit your standards specifications if they include elastomeric duct liner products. If you have standard specifications for elastomeric duct liner products, it may be worthwhile to call out specific products that you have obtained ASTM E84 reports for or remove elastomeric from the standard specification until more information is provided.

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