This paper presents an alternative environment-friendly thermal insulation material for the construction industry. This study aimed to produce this building material with superior heat resistance properties and comparable strength to the concrete produced with Ordinary Portland Cement. The primary purpose of the experimental studies is to produce a basic geopolymeric plate and to add cellubor and polypropylene fibers to the geopolymeric mortar. In the next stage, fiber-reinforced plates were prepared, thermal experiments were carried out, and discussions and conclusions were formed according to the results and findings. This study initially produced different types of fiber-based metakaolin plates with high heat resistance. Then, the flame test examined the heat resistance of the composite plates formed by the mixture of fibers consisting of cellubor, polypropylene, and cellubor + polypropylene fiber mixtures into geopolymeric mortars. It was found that the metakaolin plates containing approximately 6% by weight of Cellubor in the structure, besides their serious resistance to flame, their heat retardancy properties gave 72% better results than Kalekim (cementitious ceramic tile adhesive) plates and 55% better results than non-fiber metakaolin plates.