The trend of research and development of technological advancement in thermal insulators involves using renewable materials, selecting manufacturing processes that require the lowest possible energy, or using waste materials that may help subdue the reduction of petroleum reserves. This review discusses the potential substitution of petroleum by natural materials in thermal insulation manufacturing. This review presents an overview of the definition, properties, materials, and methods that can be used in the manufacture of thermal insulators based on results reported in the literature. Many materials are currently being investigated to produce thermal insulator such as cellulose. Cellulose fiber has a big potential to be used in the manufacture of thermal insulators because cellulose possesses many advantageous properties over petroleum-based polymers, i.e. biocompatibility, biodegradability, thermal stability, chemical stability, and low cost. Another material that may be used is silica, as it has high temperature resistance and low thermal expansion. Bagasse containing high cellulose and silica with the composition of 32-44% cellulose and 55.5%-70% silica. Therefore, bagasse proves appealing to be processed into thermal insulator. Aerogels are among the best thermal insulating materials known. This review proposes the impregnation method followed by the ambient pressure drying (APD) method to synthesize cellulose-silica aerogel. The impregnation of silica into cellulose aerogel will increase mechanical strength, flexibility, and the resulting silica-cellulose aerogel will be transparent with a very low thermal conductivity.