The present study presents a methodology to design ultra-lightweight concrete that could be potentially applied in monolithic concrete structures, performing as both load bearing element and thermal insulator. A particle grading model is employed to secure a densely packed matrix, composed of a binder and lightweight aggregates produced from recycled glass. The developed ultra-lightweight concrete, with a dry density of about 650–700 kg/m3, shows excellent thermal properties, with a thermal conductivity of about 0.12 W/(m K); and moderate mechanical properties, with a 28-day compressive strength of about 10–12 N/mm2. Furthermore, the developed concrete exhibits excellent resistance against water penetration