The Architecture, Engineering, Construction, and Operations (AECO) sector significantly contributes to global energy consumption and CO2 emissions. In response, the search for more efficient and environmentally friendly materials has intensified. Mycelium, a biological material, has gained significant attention as a circular and low-carbon solution. However, industrial secrecy often restricts the full disclosure of production processes, complicating the replication and comparison of scientific methods. This study sought to address this challenge by developing an experimental protocol and documenting the complete process for cultivating mycelium blocks using coffee husks, an abundant Brazilian agricultural residue. The method consists of five main stages: (1) preparation of the coffee husk residues, (2) inoculation with the Pleurotus ostreatus fungus, (3) colonization in reusable molds, (4) dehydration to halt fungal growth, and (5) evaluation of the blocks’ physical properties. The results demonstrated that blocks made from coffee husks exhibited low density (237.91 kg/m3) and low thermal conductivity (0.07 ± 0.88 W/m∙K.), making them a promising alternative for sustainable thermal insulation in construction. This study contributes to the development of environmentally sustainable building materials with reduced environmental impact and improved energy efficiency. It addresses the growing need for innovative solutions in the construction sector, with relevance to the Brazilian context.