No abstract

Hempcrete is a sustainable biocomposite that can reduce buildings’ embodied energy while improving energy performance and indoor environmental quality. This research aims to develop novel insulating hemp-lime composites using innovative binder mixes made of recycled and low-embodied energy pozzolans. The characterization of composites’ mechanical and hygrothermal properties includes measuring compressive strength, splitting tensile strength, thermal conductivity, specific heat capacity, and moisture buffer capacities. This study also investigates the impact of sample densities and water content on compressive strength at different ages. The findings suggest that mixes with a 1:1 binder to hemp ratio and 300−400 kg/m3 density have hygrothermal and mechanical properties suitable for insulating infill wall applications. Hence, compressive strengths, thermal conductivity, and specific heat capacity values range from 0.09 to 0.57 MPa, 0.087 to 0.10 W/m K, and 1250 to 1557 J/kg K, respectively. The average moisture buffer value for all hempcrete samples of 2.78 (gm/m2 RH%) indicates excellent moisture buffering capacity. Recycled crushed brick pozzolan can enhance the hygrothermal performance of the hemp-lime composites. Thus, samples with 10% crushed brick have the lowest thermal conductivity considering their density and the highest moisture buffer capacity. The new formulas of hydrated lime and crushed brick have mechanical properties comparable to metakaolin and hydraulic lime formulas.

Higher requirements for buildings' energy performance and indoor environmental quality have prompted new technologies such as latent heat storage with phase change materials capable of storing and releasing significant quantities of heat per unit mass near room temperature. Conventional building materials (e.g., gypsum, concrete) used for mixing with microencapsulated phase change materials (MPCM) often contain high embodied energy. Hempcrete is a sustainable biocomposite material that can significantly reduce a building's embodied energy and energy consumption while enhancing indoor environmental quality. This research aims to develop a new low-carbon latent heat storage material composed of hempcrete and MPCMs with improved hygrothermal properties for sustainable buildings. Eight hempcrete composites were created using different design mixes using hydrated lime, metakaolin, hydraulic lime, and recycled crushed brick. Furthermore, eight hempcrete-MPCM composites were made using two MPCM types, four MPCM melting temperatures, and two MPCM concentrations. The characterization of composites' thermal and moisture properties includes measuring thermal conductivity, volumetric heat capacity, and moisture buffer capacities. The findings suggest that the developed hempcrete-MPCM samples have a higher heat storage capacity than the hempcrete due to their higher volumetric heat capacity. Moreover, hempcrete-MPCM samples have lower thermal conductivity than hempcrete samples in the same density range and testing orientation. The average moisture buffering value for the hempcrete and HPCM samples of 2.78 and 2.76 (gm/m2 RH%), respectively, indicates excellent moisture buffering performance. The results suggest that the optimal integration of MPCMs requires a thorough consideration of the operating temperature and percentage of MPCMs within the hempcrete concerning the specific application and performance objectives.