The material with low thermal conductivity means it has a high insulating capability for reducing heat transfer. One of materials for insulation is cellulose. This study presents a insulation material of cellulose made from reeds imperata cylindrical type with the extraction process. The extraction of cellulose fibers to form a sheet by adding 3.5% Na-CMC (Sodium Cellulose Carboksil Metyl). The process of forming the sheet uses blender for 30 minutes, 45 minutes, and 60 minutes. Furthermore, each mixture are put into the oven with temperature of 40°C for 36 hours. There are three parameters will be investigated, i.e. thermal conductivity, density and thermal capacity. The results showed that the lowest and the highest of thermal conductivities were 0.22 W/m K and a maximum 0.36 W/m K, respectively.