Thermal Performance of Interlocking Stabilised Soil Blocks (ISSB) for Passive and Sustainable Building Design

Interlocking Stabilised Soil Blocks (ISSB) have gained increasing interest as an environmentally friendly alternative to conventional sandcrete blocks and fired bricks. However, beyond technical performance, the adoption of ISSB in Nigeria is influenced by non-technical factors such as user perception, institutional support, and industry acceptance. This study investigates the thermal performance of Interlocking Stabilised Soil Blocks (ISSB) as a sustainable walling material suitable for passive building design in tropical regions. The research employed both experimental field measurements and structured questionnaires to compare ISSB with conventional sandcrete blocks. Data from 412 respondents and temperature monitoring across selected buildings in southwestern Nigeria revealed that ISSB structures exhibited lower indoor temperature fluctuations and reduced cooling energy demand by approximately 30%. Statistical analysis confirmed significant differences (p < .05) between ISSB and sandcrete walls, demonstrating ISSB’s superior ability to maintain thermal stability and comfort. These findings validate ISSB’s potential to minimize reliance on active cooling systems, thereby advancing energy efficiency and sustainable housing objectives in developing contexts. The study contributes empirical evidence to support policy advocacy, architectural design strategies, and material optimization for climate-responsive housing solutions in Nigeria.