Fabric Air Ducts vs. Sheet Metal Ducts: Which Should Your Factory Choose?

In factory ventilation projects, you often hear two schools of thought: veteran engineers stick with sheet metal ducts, while younger colleagues recommend hanging "fabric bags" from the roof. What exactly is a fabric air duct? And how does it compare with traditional sheet metal ductwork? This article lays it out from eight angles.

First, the naming: one product, several names

Fabric air ducts — also called cloth ducts, bag ducts, sock ducts or fiber fabric ducts — are the same flexible air supply duct made of high-performance polymer fabric, delivering conditioned air evenly through the entire fabric surface via slots, micro-perforations and permeation.

An eight-point comparison

• Air distribution: Fabric ducts supply air over the entire surface with uniformity within ±5% and no draft at outlets; sheet metal ducts discharge from concentrated outlets, causing uneven temperatures.
• Roof load: Fabric ducts are extremely light — a fraction of the weight of metal ducts; sheet metal ducts are heavy and may require roof reinforcement.
• Condensation: Fabric ducts can be integrally molded with an insulation layer to prevent condensation at the source; sheet metal ducts need external insulation wrap that often fails at the seams.
• Energy use: Fabric ducts have lower resistance, better sealing and insulation, cutting fan and cooling losses; sheet metal ducts lose more.
• Installation speed: Fabric ducts assemble with modular zippers — a typical project takes 3 people 3 days; sheet metal requires on-site fabrication, welding and insulation wrapping.
• Cleaning: Fabric ducts can be removed and machine-washed, meeting GMP validation in cleanrooms; sheet metal ducts are hard to clean internally.
• Fire safety: Fabric ducts are available in GB 8624 Class A2/B non-combustible versions; sheet metal is non-combustible but conducts heat quickly and still needs insulation and fire wrapping.
• Appearance: Fabric ducts come in multiple colors and blend into the space; bare metal ductwork looks industrial.

When to choose fabric air ducts

• Large-span steel workshops and warehouses, where roof load matters
• Large spaces demanding uniform air distribution: gymnasiums, malls, theaters, showrooms
• Central air-conditioning systems prone to condensation dripping
• Pharmaceutical, electronics and food cleanrooms: washable, antimicrobial, anti-static, low particle generation
• Projects on tight schedules: modular zipper assembly is fast

When sheet metal ducts are still the first choice

• High-temperature exhaust and fire-protection ductwork requiring heat resistance and mechanical strength
• High-pressure, high-velocity systems where metal duct pressure capacity and airtightness are more mature
• Exposed areas subject to mechanical impact
• Where existing design codes mandate metal ducts

How to decide — three steps

1. Identify your pain points: air distribution uniformity, roof load, condensation, cleaning.
2. Check hard constraints: fire rating, temperature, pressure and code requirements.
3. Let the numbers decide: give the manufacturer your airflow, static pressure, span and ceiling height for airflow simulation and a side-by-side comparison.

Conclusion

There is no absolute winner — only what fits. RyboTex (Nantong) specializes in fabric air duct systems and provides CFD airflow simulation, anti-condensation calculation and full-lifecycle technical service. If you are weighing options for your plant's ventilation, bring us your project parameters and we will run an objective comparison.