Solar heat reflecting insulation coatings for buildings
1Key Takeaways
This standard specifies the terms and definitions, classification, requirements, test methods, inspection rules, signs, packaging and storage of reflective heat-insulating coatings for buildings. This standard applies to coatings made of resins, pigments and fillers, additives, functional materials, etc., which are uni…
2Expert Interpretation
This article provides an in-depth analysis of the technical requirements for reflective thermal insulation coatings for buildings as defined in the GB/T 25261-2018 standard, including the classification indicators for thermal insulation mid-coat, reflective thermal insulation flat topcoat, and textured topcoat. It focuses on the test methods and engineering application points for key parameters such as solar reflectance and near-infrared reflectance, providing a standardized basis for building energy-saving design.
Analysis of the core content of the standard
| Product type | Key indicators | Main changes in the 2018 version |
|---|---|---|
| Thermal insulation mid-coat | Thermal conductivity ≤0.15W/(m·K) | Newly added Grade 1/Grade 2 classification, and added elastic type (T type) |
| Reflective thermal insulation flat coating | Solar reflectance ≥0.85(L*>95) | Newly added brightness grading index, and strengthened performance requirements after pollution |
| Reflective and Thermal Insulating Textured Topcoat | Hemispherical Emissivity ≥ 0.85 | Incorporated into the standard system for the first time, clarifying functional requirements |
Detailed Explanation of Key Technical Indicators
Solar Reflectance: The standard requires a calculated reflectance of L*/100-0.15 in the 300-2500nm band. High-gloss coatings (L*>95) require a minimum of 0.85. Testing utilizes the spectrophotometric method specified in JG/T 235-2014. During specimen preparation, ensure that the dry film thickness is controlled within 0.15-0.50mm.
Implementation Recommendations
1. It is recommended that the insulating midcoat be applied in layers, with 24-hour intervals between coats. A total thickness of 1.0-2.0mm ensures that the thermal conductivity meets the standard.
2. When used in conjunction with a reflective topcoat, a 168-hour curing period is required. An additional 4 hours of UV aging pretreatment is recommended before pollution testing.
Standard Evolution Analysis
Major improvements compared to the 2010 version: 1) Deleted the equivalent thermal resistance calculation method; 2) Added 15 referenced standards; 3) Refined the lightness grading system; 4) Added a textured topcoat category. These changes reflect the industry's move toward precise quantification and multi-functional integration.