In HVAC systems, fiberglass ducts are widely used in commercial and public buildings due to their combined functions of air delivery, insulation, and noise reduction. However, duct systems are constantly exposed to airflow and alternating hot and cold environments, and their moisture resistance directly affects the system's stability, service life, and operational safety. This article analyzes the moisture resistance of fiberglass ducts from the perspectives of material structure and engineering applications.

Firstly, from a material composition perspective, fiberglass ducts are typically made primarily of glass fiber, bonded with resin adhesives, and coated on both the inner and outer surfaces. Glass fiber itself is an inorganic material, resistant to corrosion and mold, which is a key reason for its inherent moisture resistance. However, it's important to note that the fiber structure has some porosity; without effective protection, moisture can still penetrate the interior during long-term operation.

Secondly, the surface coating plays a crucial role in moisture resistance. Commonly used fiberglass ducts in engineering projects have aluminum foil, composite films, or other protective layers on their outer surface to prevent moisture penetration. The integrity and bonding quality of the coating directly determine the overall moisture resistance of the duct. If the cladding is damaged or the joints are not properly sealed, moisture can easily penetrate the fiberglass layer, leading to localized moisture absorption and affecting structural strength and insulation performance.

Third, the operating environment significantly impacts moisture resistance. In high-humidity areas or air conditioning systems, condensation is likely to occur on the outer surface of fiberglass ducts. If the system design does not adequately consider anti-condensation requirements, the duct will remain damp for extended periods, accelerating material performance degradation. Therefore, in such environments, a comprehensive design considering duct thickness, supply air temperature, and environmental dew point conditions is necessary to reduce the probability of moisture absorption.

Fourth, construction quality is a crucial factor affecting moisture resistance. Improper treatment of joints, interfaces, and penetration points during fiberglass duct installation can create weak points for moisture entry. Proper construction should ensure continuous joint sealing, even adhesive application, and avoid unprotected construction in high-humidity or rainy environments to reduce the risk of moisture absorption from the outset.

Fifth, from a system perspective, moisture resistance is not a single material indicator but rather the result of the combined effects of duct structure, sealing methods, and operational management. A well-designed system can effectively reduce surface temperature differences in ducts, minimizing condensation. Regular inspection and maintenance help detect damage to the lining or sealing failures promptly, preventing prolonged dampness.

In general, fiberglass ducts possess a certain degree of moisture resistance, but their performance is highly dependent on the lining design, construction quality, and system operating conditions. By selecting products with a reasonable structure and reliable lining, and by adhering to standardized construction and scientific operation management, the stability and service life of fiberglass ducts in humid environments can be effectively improved. This is also one of the key technical points for ensuring the long-term reliable operation of building insulation and HVAC systems.