The construction industry is known for its significant environmental impact during the construction and operational phases. This study aims to explore the potential of rice husk, an abundant agricultural waste, as a partial replacement for sand in cement mortar. The research evaluates the thermo-mechanical properties, including compressive strength, water absorption, thermal conductivity, specific heat, and thermal diffusivity, of cement mortar by conducting a series of laboratory experiments. One of the critical novel aspects of this study is the evaluation of the dynamic thermal performance of the cement mortar when used with different bricks. The dynamic thermal performance was assessed using a MATLAB code based on the Charted Institute of Building Service Engineers (CIBSE) 2006 standard. By increasing the percentage of rice husk as a replacement for sand, the compressive strength of the cement mortar decreases, while the thermal conductivity decreases and the water absorption capacity increases. Notably, the results reveal that a 12 % reduction in thermal conductivity can be achieved by replacing just 7 % of the sand with rice husk. Furthermore, the study establishes a linear relationship between the dynamic thermal performance of the cement mortar and its volumetric heat capacity. These findings contribute to the development of eco-friendly solutions for energy-efficient buildings. The outcomes of this research can help engineers, architects, and policymakers in the decision-making processes regarding sustainable construction practices, promoting the use of rice husk as a viable alternative to sand.