In ventilation and air conditioning systems, the sealing performance of duct systems directly affects air delivery efficiency, energy consumption, and operating noise. As a system integrating insulation and ductwork functions, the sealing performance of fiberglass ducts depends not only on the material structure but also heavily on construction techniques and installation precision.

I. Structural Basis of Fiberglass Duct Sealing Performance

Fiberglass ducts typically use fiberglass boards as the base material, covered with a protective layer of fiberglass cloth or aluminum foil. Their duct walls are continuous and lack secondary insulation joints, theoretically reducing weak points in the seal compared to traditional metal ducts with external insulation.

The duct wall itself has low permeability; air leakage mainly occurs through joints, seams, and penetration points. Therefore, the sealing performance of fiberglass ducts is primarily focused on system connection points, rather than the material itself.

II. Impact of Joint Type on Sealing Performance

Common joint types for fiberglass ducts include plug-in joints, flange joints, and specialized connectors. Joint precision and construction quality are the core factors determining sealing performance.

If the interface dimensions are accurate, the joints are smooth, and a continuous sealant or sealing strip is used, a low air leakage rate can be achieved. Conversely, misalignment, deformation, or discontinuity in the sealing material at the interface can easily create localized air leakage points, leading to a decrease in system efficiency.

III. Influence of Sealing Materials and Construction Processes

Fiberglass duct systems typically use specialized sealants, sealing strips, or composite sealing methods for sealing. The sealing material should possess good elasticity and aging resistance to withstand minor vibrations and temperature changes during system operation.

During construction, the thickness and continuity of the sealant application are particularly important. A thin layer is prone to breaks, while an excessively thick layer may affect the closure accuracy of the interface, both weakening the sealing effect.

IV. Influence of Installation Accuracy and Support Structure on Sealing Performance

Fiberglass ducts have lower rigidity than metal ducts and are more sensitive to installation accuracy. If the support and hanger arrangement is unreasonable, the duct may experience uneven stress over a long period, potentially causing micro-deformation at the interface, thus affecting the sealing condition.

Properly controlling the spacing of supports and hangers, and ensuring the straightness of the duct axis, helps maintain a stable and long-term seal at the joints, which is crucial for ensuring the system's sealing performance.

V. System Pressure Rating and Leakage Risk

Fiberglass ducts are typically used in low- and medium-pressure ventilation systems. As the system static pressure increases, the sealing requirements at the joints also increase. If fiberglass ducts are used in high-pressure systems without enhanced sealing design, the risk of leakage will significantly increase.

Therefore, during the system design phase, the duct type should be selected appropriately based on the pressure rating, and enhanced sealing measures should be implemented for critical areas.

VI. Sealing Performance Stability During Operation

During long-term operation, temperature changes, vibration, and maintenance operations will all affect the sealing areas. A high-quality sealing structure can maintain a good seal under these conditions, while systems with poor construction quality may gradually develop leaks.

Regularly inspecting joints, elbows, and equipment connections helps to promptly detect problems with deteriorating sealing performance and ensure stable system operation.

VII. Overall Evaluation

In summary, fiberglass duct systems possess excellent sealing potential structurally. Their actual sealing performance depends largely on interface design, construction techniques, and installation precision. Under standardized design and construction conditions, fiberglass ducts can meet the airtightness requirements of most HVAC systems while also providing insulation and noise reduction.

By selecting appropriate duct types during the design phase and strictly controlling splicing and sealing details during construction, air leakage rates can be effectively reduced, and system energy efficiency and operational reliability improved.