Development of a novel hemp-based building material with enhanced thermal performance

Hempcrete is a bio-based building material that has gained attention for its potential environmental benefits, including carbon sequestration and lower embodied energy compared with conventional construction materials. While it is commonly used as a low-density insulating material, its thermal performance is insufficient for applications requiring higher energy efficiency, limiting its broader adoption and incorporation in future high-performance building design. This study investigates the development of a newly patented high-performance hemp-based non-load-bearing insulation block/infill (HPHB/I) with enhanced thermal performance through the use of alternative mineral binders and the incorporation of silica aerogel granulates. Lime, magnesium oxychloride (MOC), and magnesium phosphate (MPC) binders were evaluated, and the effects of binder-to-insulation ratio and aerogel content on density and thermal conductivity were systematically examined. The results show that both binder content and aerogel incorporation significantly influence the density and thermal conductivity of HPHB/I. Increasing binder content leads to higher thermal conductivity due to enhanced conduction in the solid matrix, while the addition of aerogel reduces thermal conductivity by modifying pore structure and suppressing heat transfer mechanisms. Magnesium-based binders demonstrated improved compatibility with hemp shives, enabling stable formulations at lower binder contents. The lowest thermal conductivity achieved by incorporating aerogel into the mix was approximately 0.020 W/m·K, representing a reduction of up to four times compared to conventional hemp-lime materials. Predictive regression models were developed to generalize the combined effects of binder ratio and aerogel content. The findings demonstrate that binder and performance-enhancing agent selection are critical for optimizing and developing bio-based materials with super-insulating properties suitable for high-performance building applications.