Rock wool and polyurethane are both widely used insulation materials in building energy conservation, industrial equipment, and pipeline insulation projects. They differ significantly in fire resistance, structural form, and construction methods, and each also has its own advantages and limitations in terms of insulation performance. A systematic comparison of the insulation performance of rock wool and polyurethane is helpful for the rational selection of materials in engineering projects.

I. Differences in Insulation Mechanisms

Rock Wool Insulation Mechanism

Rock wool is an inorganic fiber insulation material, made primarily from natural minerals such as basalt, which are melted at high temperatures to create a fiber structure. Its insulation performance mainly relies on the large number of static air layers formed between the fibers, achieving a thermal insulation effect by reducing air convection and heat conduction.

Polyurethane Insulation Mechanism

Polyurethane is an organic polymer foam material with a high proportion of closed-cell structures, and the pores are filled with low thermal conductivity gases. The heat conduction path within the material is significantly prolonged, thereby significantly reducing the overall thermal conductivity.

From a mechanistic perspective, rock wool is a "fiber + air" type of insulation, while polyurethane is a "high closed-cell foam" type.

II. Comparison of Thermal Conductivity and Insulation Efficiency

Rock Wool's Thermal Conductivity

The thermal conductivity of conventional rock wool products is generally in the range of 0.035–0.045 W/(m·K). Higher density and more rational fiber arrangement result in relatively more stable insulation performance. However, overall, rock wool is considered a medium-performance insulation material.

Polyurethane's Thermal Conductivity

Polyurethane has one of the lowest thermal conductivityes among common insulation materials, typically between 0.022–0.030 W/(m·K). Under the same insulation requirements, polyurethane requires a significantly smaller thickness than rock wool.

In terms of pure insulation efficiency, polyurethane is significantly superior to rock wool.

III. Comparison of Thickness Requirements and Space Occupancy

Due to differences in thermal conductivity, to achieve the same heat transfer coefficient:

Rock wool typically requires a larger insulation thickness.

Polyurethane can achieve the same or even higher insulation effect with a thinner thickness.

Therefore, in space-constrained roofing systems, equipment insulation, or piping projects, polyurethane has an advantage in thickness control; while in walls or insulation structures where space requirements are less critical, the thickness disadvantage of rock wool has a relatively smaller impact.

IV. Comparison of Insulation Performance Stability

Rock Wool Stability

Rock wool is an inorganic material and does not undergo chemical decomposition. It maintains stable performance at high temperatures, and its thermal conductivity changes little over long-term use. However, its fiber structure is an open-cell system, and its actual insulation performance will significantly decrease once it becomes damp.

Polyurethane Stability

Polyurethane has stable insulation performance under dry, sealed conditions, but its long-term performance is highly dependent on construction quality and the protective layer. If the closed-cell structure is damaged or absorbs moisture, the thermal conductivity may gradually increase.

From a long-term stability perspective, rock wool has stronger high-temperature resistance, while polyurethane has higher requirements for moisture resistance and external protection. V. The Impact of Temperature Range on Insulation Performance

Rock wool is suitable for a wide temperature range, especially in medium- and high-temperature conditions, where its insulation performance and structural stability are outstanding. It is commonly used in industrial equipment, high-temperature pipelines, and systems with high fire protection requirements.

Polyurethane is more suitable for ambient to medium- and low-temperature environments and is widely used in cold storage, cold chain systems, and building envelopes. However, its insulation performance and material safety are limited under high-temperature conditions.

Therefore, the "effective insulation performance" of the two is not entirely the same in different temperature ranges.

VI. Comprehensive Performance Orientation in Engineering Applications

If the project focuses on:

High-efficiency insulation, reduced thickness

High energy-saving requirements

Space-constrained locations

Polyurethane has a greater advantage in insulation performance.

If the project also focuses on:

Fire safety

High-temperature stability

Structural durability

Although rock wool has slightly lower insulation efficiency, its overall performance is more balanced.

In summary, the core differences between rock wool and polyurethane in terms of insulation performance lie in their thermal conductivity and thickness requirements: polyurethane is a high-efficiency insulation material with low thermal conductivity and high insulation efficiency, suitable for projects with strict requirements on energy saving and thickness; rock wool is a medium-performance insulation material with relatively high thermal conductivity, but it has advantages in high-temperature resistance, fire resistance, and long-term stability. In actual engineering projects, a comprehensive selection should be made based on the usage environment, temperature conditions, fire rating, and construction method, rather than using insulation performance as the sole criterion.