With the deepening of green building concepts and the continuous advancement of HVAC technology, the limitations of traditional metal duct systems—particularly regarding energy consumption, noise, and installation complexity—are becoming increasingly evident. Against this backdrop, fibrous fabric ductwork (also known as textile ducts, fabric air dispersion systems, or permeable ducts) has gradually gained widespread application in commercial, industrial, and public buildings. Leveraging advantages such as lightweight construction, energy efficiency, quiet operation, and uniform airflow distribution, this system stands out as a modern alternative. Among its features, the permeation effect serves as one of the core mechanisms for achieving airflow distribution. This effect not only determines the system's air supply performance but also profoundly influences indoor thermal comfort and energy efficiency. This article systematically explores the permeation effect of fibrous fabric ductwork from the perspectives of principles, types, design considerations, and practical applications.

1. The Basic Principle of Permeation

    Fibrous fabric ductwork is typically manufactured from high-density polyester fibers or other functional synthetic materials, featuring a controllable microporous structure in its tube walls. When a fan delivers conditioned air into the duct, the internal static pressure exceeds the ambient external pressure. Consequently, air "permeates" or "seeps" outward through the fabric's micro-pores at a low, uniform velocity. This process is not random leakage but a precisely engineered, directional release of airflow.

    Unlike traditional metal ducts that rely on集中送风 (concentrated air supply) via terminal devices such as grilles and diffusers, fabric ductwork utilizes the entire surface of the tube as the supply area, creating a "surface air supply" effect. The permeation effect allows air to be released slowly at extremely low velocities (0.01~0.3 m/s). This effectively avoids the common "draft sensation" and temperature stratification associated with traditional methods, significantly enhancing indoor thermal comfort.

2. Classification and Regulation of Permeability

    The permeation performance of fabric ductwork is typically measured by "air permeability" (units: L/m²·s or CFM/ft²), representing the volume of air passing through a unit area of fabric per unit time. Depending on the application scenario, manufacturers offer products with various permeability grades:

Full-Permeation Type: The entire duct section features permeability. This is suitable for environments with high requirements for uniform temperature and humidity, such as恒温恒湿 laboratories (constant temperature and humidity labs), cleanrooms, and food processing workshops.

Partial-Permeation Type: Permeable zones are set only in specific sections, while the rest consists of non-permeable or low-permeability materials. This is used for场合 (occasions) requiring zoned airflow control, such as large warehouses and gymnasiums.

Zero-Permeation Type (Jet Type): The tube wall is completely impermeable; airflow is directionally jetted through sewn nozzles or slits. This is suitable for long-distance air supply in high-ceiling spaces.

Furthermore, fine regulation of permeability can be achieved by adjusting fabric density, coating processes, or using composite multi-layer structures. For instance, in low-temperature air supply systems, low-permeability fabric combined with local nozzles can reduce condensation risks while ensuring supply efficiency.

3. Advantages Brought by the Permeation Effect

    Uniform Air Supply and Enhanced Comfort

Permeation-based air supply avoids the localized high-speed airflow caused by traditional vents. This causes both the室内温度场 (indoor temperature field) and velocity field to trend toward uniformity, making it especially suitable for densely populated spaces or areas where people stay for long periods.

Reduced System Static Pressure and Significant Energy Savings

    Since fabric ductwork inherently possesses a distribution function, it eliminates the need for numerous elbows, reducers, and terminal devices, drastically reducing system resistance. Research indicates that compared to traditional metal ducts, fan energy consumption can be reduced by 20%~40%.

Condensation Suppression and Improved Hygiene

    During low-temperature operation, the permeating airflow forms a thin "air protection film" outside the管壁 (duct wall). This effectively isolates the wall from direct contact with humid air, significantly lowering the risk of dew formation. Simultaneously, the fabric material itself can be antibacterial and mold-resistant, and is easy to dismantle and clean, which benefits the maintenance of indoor air quality.

Convenient Installation and Low Maintenance Costs

    Fibrous fabric ductwork weighs only 1/20th of metal ductwork. It utilizes suspension installation, resulting in short construction cycles. Moreover, it does not require an insulation layer (some models have built-in thermal insulation functions), making the overall cost more competitive.

4. Key Design Considerations

    Despite the numerous advantages of the permeation effect, the following points must be noted during engineering design:

    Static Pressure Matching: Permeability is closely related to system static pressure. If the pressure is too low, the permeation volume will be insufficient; if too high, it may cause excessive airflow velocity, compromising comfort. Therefore, the required static pressure must be accurately calculated based on airflow volume, duct diameter, and permeability.

    Condensation Control: When supplying cold air in high-temperature and high-humidity environments, it is essential to verify whether the external surface temperature of the duct wall is below the dew point temperature. If necessary,防凝型织物 (anti-condensation fabrics) with PE coatings or auxiliary heating measures should be selected.

    Fire Protection and Environmental Requirements: The fabric material must comply with local building fire codes (e.g., GB 8624, UL 94) and environmental standards to avoid releasing harmful substances.

    Airflow Organization Simulation: For complex spaces, it is recommended to use CFD (Computational Fluid Dynamics) simulations to verify whether the permeation air supply can effectively cover the target area, avoiding dead zones or short-circuiting.

5. Typical Application Cases

    In a large cold chain logistics center project, the traditional metal ductwork frequently suffered from condensation and dripping issues during low-temperature operation, severely affecting goods storage safety. After switching to fibrous fabric ductwork, the "dry air layer" formed by the permeation effect effectively prevented condensation. Simultaneously, the uniform cold airflow ensured temperature consistency within the warehouse, achieving an annual energy saving rate of 28%.

    In another case involving a university gymnasium with a 15-meter ceiling and high human activity intensity, a combined partial-permeation and jet-type fabric duct was adopted. The upper section slowly displaced hot air via permeation, while the lower section used directional nozzles to meet the fresh air demand in the运动区域 (activity zone). This achieved a unity of high efficiency, energy saving, and comfort.

Conclusion

    The permeation effect of fibrous fabric ductwork is not only a core technical feature distinguishing it from traditional ducts but also the key to achieving efficient, comfortable, and energy-saving ventilation. With the development of materials science and intelligent control technologies, future fabric ductwork is expected to integrate functions such as humidity sensing, self-regulating permeation, and photocatalytic purification. This will further expand its application prospects in高端领域 (high-end fields) such as healthy buildings, data centers, and medical facilities. Driven by the "Dual Carbon" goals, this green ventilation technology is bound to usher in broader development space.