In this work compositions containing two different wastes, transparent glass bottles, TGB (50-70%), and sludge from sewage treatment plants, STP (30-50%), and pore forming, CaCO3 (2-10%), were prepared for the production of thermal insulators. The mixed raw materials of the formulated compositions were uniaxially pressed (40 MPa) and the powder compacts were dried (110°C/2 h) and fired in the temperature range between 750 and 1000 °C with holding times from 15 to 60 min. The raw materials and obtained materials were characterized in terms of their chemical, physical and microstructural properties. The results showed that it is possible to produce thermal insulators from optimized compositions containing 70% TGB, 30% STP and 5% CaCO3 and fired between 750 and 1000 °C for 60 min. The fired materials showed porosities between 3 and 62% with thermal conductivities between 1.25 and 0.5 W/m.K and compressive strength ranging from 8.7 to 5.4 MPa. On the basis of the obtained results it can be said, in general terms, that obtained porous materials are strong candidates for structural applications such as panels for thermal insulation which require an adequate combination ofthermal conductivity, porosity and mechanical strength.