The walls in architecture determine the energy behavior of a home, the physical and thermal properties of the building elements are capable of controlling the energy transfer of to the interior, avoiding dependence on artificial cooling systems, which increase energy consumption. The research takes advantage of the physical-thermal attributes of straw, considering its use as a material, presenting sustainable constructive solutions for the walls configuration in rural houses with a warm tropical climate. The proposed design starts from identifying the properties of materials with a low carbon footprint such as straw, wood, cardboard, which are viable due to their low weight and easy obtaining. The result is the modular design of the EcoStraw panel that consists of a compressed straw matrix, embedded in a module whose function is to isolate the heat conduction between the interior and exterior, a modular and wooden support structure with the aim of giving structural stability in the stack and a cardboard laminate lining that acts as an interior closing surface. The constructive solution can be industrialized, economical and with a low impact on the environment.