008 Research Progress on Insulation Material Filling Ratio and Its Impact on the Thermal Performance of Hollow Brick Walls

Abstract

Improving the thermal performance of masonry walls is critical for reducing building energy consumption. This study presents a focused review of the insulation material filling ratio (IMFR) as a key design parameter for enhancing the thermal performance of sintered hollow brick walls. The paper systematically synthesizes experimental and numerical studies investigating how different IMFR levels influence both steady-state (U-value, heat flux) and dynamic thermal indicators (time lag and decrement factor). By comparing low, medium, and high filling rate strategies, this review identifies their respective thermal benefits, cost-effectiveness, and construction implications. The results indicate that increasing IMFR generally reduces thermal transmittance and improves thermal inertia, while performance gains tend to diminish beyond a certain filling threshold. Medium filling rates (approximately 50–80%) are most frequently reported as offering an optimal balance between thermal improvement and economic feasibility. Based on the synthesized evidence, key research gaps and future directions are identified, including multi-climate validation, composite filling strategies, and life-cycle-based optimization. This review provides a structured reference for the energy-efficient design and engineering application of insulation-filled hollow brick walls.