In modern building HVAC systems, the thermal insulation performance of duct systems directly affects energy consumption control, air supply efficiency, and operational stability. Fiberglass ducts, as a composite duct system integrating air supply, thermal insulation, and a certain degree of sound absorption, are widely used in office buildings, commercial buildings, and public buildings. This article will explain the thermal insulation principle of fiberglass ducts to help clarify the mechanism of their thermal insulation performance.

I. What is a Fiberglass Duct?

Fiberglass ducts typically use fiberglass insulation boards as the core material, manufactured through processes such as cutting, grooving, and splicing. Their inner and outer surfaces can be laminated with different facing materials according to usage requirements.

From a material properties perspective, fiberglass ducts belong to a composite duct system based on inorganic fibers, possessing inherent thermal insulation properties, eliminating the need for an additional independent insulation layer.

II. Overview of the Insulation Principle of Fiberglass Ducts

The insulation principle of fiberglass ducts mainly stems from the synergistic effect of the following three aspects:

1. Suppression of heat conduction by the fiberglass structure

2. Insulation effect of the static air layer inside the material

3. Comprehensive control of heat exchange by the composite structure

These factors work together to effectively reduce heat loss during the transportation of hot and cold air in fiberglass ducts.

III. Suppression of Thermal Conductivity by the Fiberglass Structure

1. Interlaced Fiber Structure Extends the Heat Flow Path

The core material of fiberglass ducts is formed by a large number of fine glass fibers randomly interlaced. When heat is transferred within the material:

The heat flow needs to constantly change direction

The heat transfer path is significantly lengthened

The thermal resistance increases accordingly

This complex fiber network structure is the basis for the insulation effect of fiberglass ducts.

2. Controlled Proportion of Solid Fibers in Thermal Conductivity

Compared to dense materials, the proportion of glass fiber in the overall structure is limited, and the solid heat transfer path is dispersed, thereby effectively reducing the overall thermal conductivity.

IV. Insulation Mechanism of Static Air Layer

Fiberglass ducts contain numerous tiny pores filled with air. Air itself has a low thermal conductivity, and when confined within the fiber structure:

Air convection is difficult to form.

Heat transfer relies primarily on slow molecular conduction.

This constitutes a crucial insulation barrier for fiberglass ducts, minimizing temperature drop during the transport of hot and cold air.

V. Comprehensive Control of Heat Exchange by Composite Structures

1. Impact of Inner and Outer Coverings on Thermal Radiation

Fiberglass ducts typically have appropriate covering materials on both the inner and outer surfaces:

The inner covering reduces heat exchange caused by air friction.

The outer covering helps reduce the impact of external heat on the duct.

This multi-layered structure further enhances the stability of overall insulation performance.

2. Integrated Duct Structure Reduces Thermal Bridges

Fiberglass ducts integrate insulation functions, reducing the thermal bridge problems caused by supports and joints in traditional metal ducts, thus structurally reducing the risk of heat leakage.

VI. Thermal Insulation Performance of Fiberglass Ducts in HVAC Systems

1. Thermal Insulation During Cold Air Delivery

In air conditioning cooling mode, fiberglass ducts can:

Reduce supply air temperature loss

Reduce the risk of condensation on the duct's outer surface

Improve the stability of terminal air delivery

2. Thermal Insulation During Hot Air Delivery

In heating systems, fiberglass ducts help to:

Improve thermal energy utilization

Reduce system energy consumption

Stabilize indoor temperature distribution

In summary, the thermal insulation principle of fiberglass ducts essentially stems from the composite insulation system formed by the fiberglass structure and the still air layer. By inhibiting heat conduction, limiting air convection, and reducing thermal bridging effects, fiberglass ducts achieve stable and continuous thermal insulation in HVAC systems. Under reasonable design and standardized construction conditions, fiberglass ducts not only contribute to energy-saving operation but also improve the overall system reliability.