Density, measured in kilograms per cubic meter (kg/m³), is a critical indicator of XPS foam’s mechanical and thermal performance. Higher density directly correlates with:
- Increased Compressive Strength: A 35kg/m³ board can withstand significantly higher permanent loads (e.g., 300 kPa) than a 25kg/m³ board (e.g., 150 kPa), making it essential for floors, parking decks, and green roofs.
- Improved Dimensional Stability: It resists shrinking, warping, or deforming under temperature fluctuations and load over time.
- Slightly Enhanced R-Value: While all XPS has excellent insulation, higher-density boards often have a marginally better long-term thermal resistance (LTTR) R-value.
- Better Workability: Higher-density boards cut cleaner and have a smoother surface, which is beneficial for precise applications and lamination. For most construction, 30-35kg/m³ is standard. For heavy-duty civil engineering projects, densities of 40kg/m³ and above are used.
