Globally, the key issues related to technology and materials are the reasonable consumption of exhaustible resources, increasing technological efficiency, reducing waste, and sustainable production. The construction industry is responsible for huge carbon dioxide emissions and other harmful waste in this context. Moreover, it requires about 16 percent of the world's annual energy use for the production of cement-based products. Experts estimate that without effective changes, the negative impact on the environment and consumption will increase to 25% by 2050. This paper presents a geopolymer based on expanded perlite up to 85% that can be used as a modern lightweight thermal-insulation construction material. The results showed that the density of the samples varied from 330 kg/m3 to 510 kg/m3, the bending strength was from 1 MPa to 2 MPa, the compressive strength was from 13.5 MPa to 21 MPa, the thermal conductivity was from 0.09 W/m K to 0.130 W/m K, the water absorption coefficient was from 77% to 137%, and the total porosity of the material was from 60% to 65%. The results meet the requirements for lightweight building materials for wall construction regarding the leading indicators. Still, high water absorption significantly decreases strength and thermal conductivity after 100 h of the aging process. To reduce the water absorption of the perlite-based geopolymer, research is planned to apply a hydrophobic coating based on metakaolin.