Fabric vs metal ducting – 4 real differences

When undertaking a new construction or renovation project, the air diffusion system is near the top of the list of considerations to ensure high indoor air quality (IAQ). For decades, the construction industry overwhelmingly looked to traditional metal-based ducting HVAC solutions. However, today more and more architects, engineers, and contractors are embracing the many benefits of fabric-based air diffusion. Since the two products essentially perform the same function, what are the real differences between them?

Michael G. Mortensen

Engineering Manager, Denmark

Materials impact longevity, performance

The most obvious difference between metal and fabric-based ducts is in the materials. Metal ducts most often are made of steel and most fabric ducts are made of polyester. While many assume that metal ducting is more durable, it is common for fabric ducts to still be in service decades beyond the original installation date. And fabric duct also reduces the load on structures.

A less obvious but very important difference is in how the two materials handle condensation and corrosion. For example, an improperly maintained, high humidity environment will eventually take a toll on any metal surface. You may think of the sweating ductwork in a café dripping on your table. While that is undesirable, a real problem is that rust and corrosion can affect the structural supports for the ductwork. The condensation that forms on metal ducts and other metallic materials in this environment expedites metal degradation and eventually leads to rust that can fall with the condensation, oftentimes endangering people’s health.

Unlike metal, the inherent properties of fabric duct do not require special coatings or maintenance to protect against corrosion or rust. When fabric ductwork is specified as permeable, which allows air to pass through the entire fabric weave, condensation and the accompanying corrosion on the material are prevented.

Transportation, and installation effect cost

Bulky, heavy metal duct versus flexible, light fabric duct also draw a distinction between the two, especially in transportation and installation and even with the cost of the structure. Metal ducts usually require large commercial vehicles for transportation. Heavy machinery, special fasteners and tools and a team of trained personnel are needed for installation, which can take weeks to complete. Large metal ductwork often requires special structural and seismic considerations.

Fabric ducts come in small, individual boxes that require very little space during transport and are usually delivered by local parcel services. Installation is done with standard tools and requires no special knowledge as the individual duct segments are simply zipped together according to the instructions on the packaging. Installation usually is completed in a few days by just a couple of people or even by one person if necessary. The installation process for fabric ducts is up to five times faster compared to metal ones.

Price the entire process

During these days of high raw materials costs adversely impacting HVAC manufacturers and their pricing, fabric air diffusion systems are becoming more and more appealing.

Since fabric duct systems are engineered solutions, it is virtually impossible to give exact cost savings over metal. However, conservative estimates show that fabric air diffusion systems can save at least 30% on costs compared to metal. And when costs are broken down to include transportation, installation, and maintenance, total savings of fabric over metal can be as high as 70%. Depending on project size, cost savings can be significant with no negative impact on HVAC performance, while maintaining the highest levels of IAQ.

Compare applications and innovation

While traditional ducts have long been a reliable and relatively static solution in most HVAC applications, through constant innovation fabric ducts are increasingly covering more applications. Thanks to the permeable, antimicrobial, and fire-resistant properties of fabric ducts, fabric-based solutions can be used in applications ranging from sports complexes, food processing, or manufacturing plants to laboratories, cinemas, warehouses, and shops. And with advanced special printing technology, fabric ducts can enhance interior design aesthetics, either by choosing a standard or customized colors or by creating distinctive visuals by printing company logos or unique patterns.

Currently, fabric duct solutions represent approximately 10% of the global HVAC market, and the demand continues to grow annually. Whether a project requires only a few feet of ducting or hundreds of yards, fabric duct is the right solution for small and big projects as this product saves time and money without sacrificing quality.

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