Glass wool is a widely used inorganic fiber insulation material in building energy conservation, HVAC, and industrial insulation systems. When evaluating the insulation performance of glass wool, thermal conductivity is one of the most crucial technical indicators. So, what is the thermal conductivity of glass wool? What factors affect its thermal conductivity coefficient?

This article will systematically analyze the thermal conductivity of glass wool from the perspectives of material structure, heat conduction mechanism, and practical applications.

I. Basic Material Properties of Glass Wool

Glass wool is an inorganic fiber insulation material, mainly made from inorganic minerals such as quartz sand, limestone, and soda ash. These are melted at high temperatures, drawn into fibers, and then cured and molded into boards or felts.

From a material property perspective, glass wool has the following characteristics:

Long, fine, and soft fibers

High internal porosity

Lightweight structure

Non-combustible or flame-retardant

Stable thermal conductivity

These characteristics lay the foundation for the good thermal insulation effect of glass wool.

II. What is Thermal Conductivity? The Significance of Thermal Conductivity

The thermal conductivity performance is usually measured by the thermal conductivity (λ value), with units of W/(m·K).

The lower the thermal conductivity value, the stronger the material's ability to prevent heat transfer, and the better its insulation performance.

Under the same thickness and operating conditions:

Low thermal conductivity → Slow heat transfer → Good insulation effect

High thermal conductivity → Fast heat transfer → Relatively weak insulation effect

Therefore, the quality of the thermal conductivity of glass wool directly determines its actual energy-saving effect in building and industrial insulation.

III. Structural Basis for the Thermal Conductivity of Glass Wool

1. The Influence of the Interwoven Fiber Structure on Thermal Conductivity

Glass wool is composed of a large number of fine glass fibers randomly interwoven, forming a complex three-dimensional structure. When heat is conducted in the material, it needs to constantly change its direction of propagation, thus:

Lengthening the heat flow path

Increasing thermal resistance

Reducing overall heat transfer efficiency

This is one of the important reasons for the relatively low thermal conductivity of glass wool.

2. High Porosity and Static Air Layer

Glass wool contains numerous tiny pores filled with air. Air itself is a medium with extremely low thermal conductivity. When air is confined within a small space:

Convection is almost impossible.

Heat transfer mainly relies on slow molecular conduction.

This significantly reduces the overall thermal conductivity of the material.

IV. Main Factors Affecting the Thermal Conductivity of Glass Wool

1. Bulk Density

The bulk density of glass wool directly affects its thermal conductivity:

Too low a bulk density: Loose structure, increased airflow, potentially leading to micro-convection.

Too high a bulk density: Increased proportion of solid fibers, enhanced solid thermal conductivity.

Therefore, glass wool typically exhibits more stable thermal conductivity within a reasonable bulk density range.

2. Fiber Diameter and Distribution Uniformity

Finer and more uniformly distributed fibers:

Further finer pore structure.

More restricted airflow.

More favorable thermal conductivity.

This is also a key reason why high-quality glass wool exhibits more stable thermal conductivity. 3. The Influence of Moisture Content

Water has a much higher thermal conductivity than air. Once glass wool absorbs moisture:

Air in the pores is replaced by water.

The rate of heat transfer increases significantly.

Therefore, in practical applications, using a moisture barrier or covering material helps maintain the original thermal conductivity of the glass wool.

4. Operating Temperature Range

Within the typical temperature range of buildings and HVAC systems, the thermal conductivity of glass wool is relatively stable. However, as the temperature rises:

The proportion of heat radiation transfer increases.

The thermal conductivity may change to some extent.

Appropriate selection can ensure its stable insulation effect within the design conditions.

V. Performance of Glass Wool's Thermal Conductivity in Practical Applications

1. Building Envelope Insulation

In exterior wall, roof, and partition systems, glass wool, with its low thermal conductivity, effectively reduces indoor and outdoor heat exchange, improving building energy efficiency.

2. HVAC System Applications

In ductwork and equipment rooms, glass wool not only reduces heat loss but also addresses sound absorption and noise reduction requirements to some extent, making it a common insulation material in HVAC systems.

3. Industrial Insulation

In insulation of medium- and low-temperature industrial equipment and pipelines, glass wool exhibits stable thermal conductivity and is lightweight, facilitating construction and maintenance.

VI. Comparison of Glass Wool's Thermal Conductivity with Other Insulation Materials

Compared to some organic insulation materials, glass wool possesses the following characteristics:

Stable thermal conductivity

Does not participate in combustion

Does not easily soften at high temperatures

Low performance degradation over long-term use

This gives it a significant advantage in scenarios requiring safety and durability.

Overall, the excellent thermal conductivity of glass wool stems from its composite insulation system formed by its dense fiber structure and high porosity. By effectively reducing heat conduction, suppressing air convection, and minimizing heat exchange, glass wool plays a stable and reliable insulation role in the building and industrial sectors. Under proper selection and standardized construction conditions, glass wool is a mature insulation material that balances energy efficiency, safety, and practicality.