How to Handle High Thermal Conductivity in Elastomeric (Rubber-Plastic) Insulation Materials
The thermal conductivity (k-value) of elastomeric insulation is the key factor determining its efficiency. If the measured thermal conductivity is higher than specified, the insulation may underperform, leading to increased energy consumption and potential condensation problems. The causes can be material-related, environmental, or installation-related, and the solutions depend on identifying the root cause.
1. Common Causes of High Thermal Conductivity
1.1 Material-Related Causes
Poor foam quality: Excessive open-cell structure reduces thermal resistance.
Binder or additive inconsistency: Affects foam structure and insulation properties.
Excess moisture absorption: Water drastically increases thermal conductivity.
1.2 Environmental or Storage Factors
Exposure to humidity or water: Insulation absorbs moisture during storage or on-site.
High ambient temperature: Prolonged heat exposure can degrade cellular structure.
1.3 Installation-Related Causes
Compression: Over-compressed boards or rolls reduce trapped air, increasing thermal conductivity.
Gaps or misalignment: Thermal bridges allow heat to bypass insulation.
Incorrect facing or vapor barrier installation: Moisture ingress increases k-value.
2. Detection and Verification
Measure thermal conductivity using heat flow meter or guarded hot plate according to ASTM C518 or EN 12667.
Check material density and thickness; deviations from design can affect thermal performance.
Inspect moisture content; closed-cell elastomeric foam should remain below 2–3% water absorption.
Visual inspection for compression, damage, or gaps.
3. Corrective Measures
3.1 Material-Level Solutions
Replace substandard insulation with high-quality closed-cell elastomeric foam.
Ensure raw material and production process meet manufacturer specifications.
Verify hydrophobic treatment is effective to prevent moisture absorption.
3.2 Installation Improvements
Avoid over-compressing boards or rolls; maintain specified thickness.
Ensure tight joints, minimal gaps, and proper sealing of seams and penetrations.
Install continuous vapor barriers to prevent condensation.
For pipe insulation, use pre-formed tubes where possible to reduce gaps and compression.
3.3 Environmental Control
Store materials in dry, ventilated areas before installation.
Protect insulation from water and UV exposure during construction.
Allow insulation to dry if moisture exposure occurs before sealing.
3.4 Thickness Adjustment
If unavoidable, compensate for slightly higher k-value by increasing insulation thickness according to design requirements.
4. Preventive Strategies
Procure materials only from reputable suppliers with consistent quality control.
Conduct on-site inspection for moisture, compression, and installation errors.
Train installation teams to follow proper procedures for cutting, fitting, and sealing.
Regularly check and maintain insulation in high-humidity or critical systems.
5. Summary
High thermal conductivity in elastomeric insulation is usually due to material defects, moisture, compression, or installation errors. By combining quality materials, correct installation practices, environmental protection, and proper maintenance, the insulation performance can be restored or maintained to design specifications.
References
ASTM C534 – Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Pipe and Tube Form.
EN 14304 – Flexible Elastomeric Foam Insulation Products for Building and Industrial Installations.
ASHRAE Handbook – HVAC Systems & Equipment, 2022.
ISO 12241 – Thermal Insulation for Building Equipment and Industrial Installations.
GB/T 17794-2008 – Rubber and Plastic Thermal Insulation Board, Pipe, and Roll Products.
