In HVAC systems, ductwork is a crucial component for air transport, and its material selection directly impacts system energy efficiency, noise levels, and construction costs. Currently, the most common duct types used in engineering projects include fiberglass ducts and galvanized iron ducts. These two types differ significantly in structure and performance. This article will systematically analyze the differences between fiberglass ducts and galvanized iron ducts from multiple dimensions to help engineering projects make more informed selections.

I. Differences in Material Composition and Structural Form

1. Structural Characteristics of Fiberglass Ducts

Fiberglass ducts use high-density fiberglass sheets as the main material, processed through composite manufacturing, typically integrating the duct structure, insulation layer, and sound-absorbing layer. Its internal structure is porous fiber, and the outer layer is often covered with a moisture-proof or protective coating.

2. Structural Characteristics of Galvanized Iron Ducts

Galvanized iron ducts use galvanized steel sheets as the base material, processed through folding and seaming. The duct itself does not possess insulation or sound absorption functions, usually requiring the addition of an additional insulation layer later. Structurally, this is the most fundamental difference between the two duct systems.

II. Comparison of Thermal Insulation Performance

Insulation Advantages of Fiberglass Ducts

Fiberglass ducts have a low thermal conductivity, effectively reducing energy loss during the transport of hot and cold air. No additional insulation layer is required, contributing to energy efficiency.

Insulation Methods of Galvanized Iron Ducts

Galvanized iron ducts have high thermal conductivity and virtually no insulation properties. Secondary insulation using materials such as glass wool and rubber/plastic composites is necessary.

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III. Differences in Sound Insulation and Noise Reduction Performance

Fiberglass ducts have a porous internal structure with excellent sound absorption properties, effectively reducing airflow noise and system operating noise.

Galvanized iron ducts have smooth inner walls, resulting in significant airflow noise reflection. They typically require additional silencers or silencing sections.

In buildings with high acoustic requirements, fiberglass ducts are more advantageous.

IV. Comparison of Weight and Construction Ease

1. Weight Difference

Fiberglass ducts are lighter overall, reducing the difficulty of hoisting and the load requirements on the building structure.

2. Construction Method

Fiberglass ducts can be quickly cut and assembled on-site, resulting in a relatively short construction period.

Galvanized iron ducts involve more processing steps, and insulation is required after installation, leading to a longer overall construction period.

V. Fire Resistance and Safety Analysis

Fiberglass Duct Fire Resistance

The base material of fiberglass ducts is an inorganic material with good fire resistance, meeting the corresponding fire protection design requirements in HVAC systems.

Galvanized Iron Duct Fire Resistance

The metal body of galvanized iron ducts is non-combustible, but the fire resistance rating of the external insulation layer needs to be assessed separately. The system's fire resistance depends on the overall structure.

VI. System Maintenance and Service Life Comparison

Fiberglass duct systems have a high degree of structural integration, reducing the occurrence of insulation layer detachment and condensation problems.

Galvanized iron ducts, due to their multi-layered structure, require attention to insulation layer aging and thermal bridging issues during long-term use.

In terms of maintenance and management, fiberglass ducts are more conducive to stable system operation.

VII. Typical Application Scenarios

**Fiberglass Duct Application Scenarios:**

Office buildings, shopping malls, and other public buildings

Hospitals, schools, and other places with high noise requirements

HVAC systems requiring both energy efficiency and comfort

**Galvanized Iron Duct Application Scenarios:**

Industrial plants and equipment rooms

High-velocity, high-volume air delivery systems

Situations requiring high structural strength

VIII. How to Make a Reasonable Choice in Projects

In actual projects, duct selection should comprehensively consider the following factors:

Building type and function

Requirements for thermal insulation and noise control

Construction period and space conditions

Overall project cost and maintenance needs

Fiberglass ducts and galvanized iron ducts are not simple substitutes, but rather suitable for different project needs.

In general, the main differences between fiberglass ducts and galvanized iron ducts lie in their structural form, thermal insulation and sound insulation performance, construction methods, and system integration. Fiberglass ducts are better suited to the energy-saving and comfort requirements of modern buildings, while galvanized iron ducts still hold advantages in specific industrial and high-intensity applications.

During the project design phase, proper selection based on building function and system requirements is crucial for ensuring the long-term stable operation of the duct system.