Thermal Insulation for Prefabricated House Roofs

Thermal insulation for prefabricated house roofs can be achieved through various scientific methods, requiring a combination of material properties and structural optimization to enhance insulation performance.

1. Cavity Insulation Structure Adopting a three-layer composite structure is an efficient insulation solution: the bottom layer is paved with red bricks as the foundational support, the middle layer is equipped with insulation boards (such as polystyrene foam boards or rock wool boards), and the top layer is covered with red bricks to form a protective layer. Key parameters must be strictly controlled: the cavity height should be greater than 5 cm to ensure air circulation, the spacing between red bricks should not exceed 15 cm to maintain structural stability, and the ground should be designed with a slope (typically 2%-3%) and include drainage features to prevent water accumulation from affecting the insulation layer's performance. This structure blocks heat conduction through the air layer and combines the low thermal conductivity of the insulation boards to significantly reduce indoor temperature fluctuations.

2. Application of Surface Insulation Materials

• Insulation Brick Paving: Choose ceramsite concrete insulation bricks or expanded perlite bricks with a thermal conductivity lower than 0.23 W/(m·K) and lay them directly on the roof surface. Their porous structure can store air, reducing heat transfer, while ensuring that the brick joints are filled with sealing materials (such as silicone sealant) to avoid thermal bridge effects.
• Reflective Insulation Coating Application: Use high-reflectivity coatings containing aluminum foil or ceramic particles (with a solar reflectance ratio ≥ 0.85), applying a thickness of 0.3-0.5 mm. Such coatings can reflect over 80% of solar radiation and emit long-wave thermal energy, suitable for hot summer regions, but require regular maintenance (reapplication every 3-5 years) to maintain performance.

3. Ecological Insulation Technologies

• Roof Greening: Lay drainage boards and filter cloth on the waterproof layer, then cover with lightweight planting soil (thickness ≥ 10 cm), and plant shallow-rooted, drought-resistant plants like Sedum lineare. The transpiration of vegetation consumes a large amount of heat, while the soil layer provides additional insulation, but structural load-bearing (approximately 60-100 kg per square meter increase) and irrigation system design must be considered.
• Water Storage Insulation: Set up a water storage tank on the roof (depth 15-30 cm), utilizing water's specific heat capacity (4.2×10³ J/(kg·℃)) to absorb heat. A concrete structure with a waterproof rating ≥ P8 should be used, and overflow ports and drainage pipes should be installed to prevent leakage due to excessive water levels. This method is suitable for regions with uniform annual precipitation, and the tank should be emptied in winter to prevent freezing.

4. Selection of Prefabricated Insulation Boards Common cement-based insulation boards in the market should pay attention to the following parameters:

• Flexural Strength: ≥ 1.5 MPa (suitable for pedestrian roofs) or ≥ 3.5 MPa (for roofs requiring equipment loading);
• Compressive Strength: ≥ 0.4 MPa (lightweight type) or ≥ 1.0 MPa (heavy-duty type);
• Operating Temperature: -40℃ to +80℃ (low-temperature crack resistance should be verified in northern regions);
• Brand Selection: Prioritize products certified by GB/T 19686-2015, such as those from Beijing New Building Materials (BNBM) or Knauf, with thermal conductivity as low as 0.032 W/(m·K).

Implementation Recommendations: Before insulation renovation, assess the roof's load-bearing capacity; for old houses, structural reinforcement is recommended first. Combining multiple solutions (such as cavity structure + reflective coating) can enhance overall insulation performance. After construction, thermal performance testing (such as with an infrared thermal imager) should be conducted to ensure the insulation layer is defect-free.