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In building energy efficiency, industrial insulation, and HVAC systems, rock wool and rubber foam are two of the most widely used insulation materials. While their thermal conductivity values are relatively similar, they differ significantly in material composition, fire performance, moisture resistance, installation methods, and application scenarios.
Understanding these differences helps project owners, designers, and contractors make informed decisions that balance performance, safety, and cost.
Rock wool is manufactured from natural stone, such as basalt, melted at high temperatures and spun into fibers. It is a typical inorganic fibrous insulation material. The interwoven fiber structure traps large amounts of still air, which is the key to its thermal insulation performance.
Main raw materials: Basalt, mineral slag
Material characteristics: Inorganic, non-combustible, structurally stable
Thanks to its inorganic nature, rock wool naturally performs well in high-temperature and fire-resistant applications.
Rubber foam insulation is produced using rubber materials (such as NBR or EPDM) combined with foaming agents to create a structure of independent closed cells. This structure provides both thermal insulation and moisture resistance.
Main raw materials: Rubber-based polymers with foaming systems
Material characteristics: Flexible, high closed-cell rate, excellent moisture resistance
Its flexibility and closed-cell structure make rubber foam particularly suitable for complex piping systems and low-temperature applications.
| Performance Item | Rock Wool | Rubber Foam |
| Thermal conductivity (λ) | Approx. 0.035–0.045 W/m·K (depending on density and fiber orientation) | Approx. 0.035–0.040 W/m·K |
| Insulation performance | Excellent (especially for high-temperature environments) | Excellent (ideal for low- and medium-temperature applications) |
| Operating temperature range | Up to 650°C or higher | Typically -50°C to +120°C (varies by formulation) |
Explanation:
Although the numerical thermal conductivity values are close, the real difference lies in temperature stability. Rock wool maintains insulation performance under high temperatures, while rubber foam performs better in low-temperature and thermal cycling conditions.
Rock wool: Classified as A1 non-combustible material. It does not burn, drip, or contribute to fire spread, and can act as a fire barrier.
Rubber foam: Typically rated B1 or B2 (depending on formulation). It offers flame retardancy but is not fully non-combustible and may melt or carbonize under direct flame.
Rock wool: Fibers may be released during installation; proper protection is required. Once installed and enclosed, it is stable and safe.
Rubber foam: Fiber-free, cleaner during installation, and more suitable for indoor mechanical systems.
Rock Wool
Rock wool has a certain level of water absorption. In humid environments, it must be used with waterproof layers or vapor barriers. Without proper moisture protection, insulation performance may deteriorate over time.
Rubber Foam
Due to its closed-cell structure, rubber foam absorbs minimal moisture and provides inherent vapor resistance. It effectively prevents condensation and maintains long-term insulation performance.
Commonly supplied as boards or rolls
Installation involves cutting, fixing, and sealing
Requires higher construction standards and skilled labor
It is more suitable for large-area, regular structural insulation systems.
Supplied as sheets, rolls, or preformed pipe sections
Highly flexible, ideal for elbows, valves, and irregular components
Faster installation and easier maintenance
Rubber foam significantly reduces installation time in HVAC and piping systems.
| Application | Rock Wool Advantages | Rubber Foam Advantages |
| Building envelopes (walls & roofs) | Fire resistance, sound insulation | Lightweight, reduced thermal bridging |
| High-temperature industrial pipes & equipment | Suitable for boilers and hot systems | Suitable for medium- and low-temperature water systems |
| HVAC refrigerant & chilled water pipes | Suitable for fire-rated zones | Excellent condensation control |
| Warehouses & cold storage | Effective as bulk insulation | Easier installation for piping and details |
| Cost Factor | Rock Wool | Rubber Foam |
| Material cost | Medium to low | Medium to high |
| Installation cost | Higher (labor and protective measures required) | Lower (simple and fast installation) |
| Overall cost efficiency | More economical for large-area applications | More cost-effective for complex systems |
Additional note:
Material price alone does not reflect total project cost. Labor efficiency, moisture protection requirements, and long-term maintenance must also be considered.
Based on temperature requirements
High temperature or fire-critical areas: Rock wool
Low to medium temperature systems: Rubber foam
Based on environmental conditions
High humidity or condensation risk: Rubber foam
Dry environments and structural insulation: Rock wool
Based on system type
Building envelope insulation: Rock wool preferred
HVAC and piping systems: Rubber foam is more suitable
Rock wool is ideal for applications requiring high fire resistance, safety, and thermal stability at elevated temperatures.
Rubber foam excels in applications where moisture resistance, condensation control, and installation flexibility are critical.
In modern construction and industrial projects, a combined system approach, using rock wool and rubber foam in different areas according to performance requirements, has become the industry standard.
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