Thermal insulation is one of the key aspects for achieving energy efficient buildings. The superinsulating properties of hollow silica nanospheres, make them ideal candidate as potential nano insulating materials for energy efficient buildings and other applications. A small inner diameter and a thin wall thickness are generally required for hollow silica nanospheres to achieve as low thermal conductivity as possible. In this work Hollow Silica Nanospheres with raspberry-like morphology with a pore diameter of about 100-300 nm and a shell thickness of 10−30 nm have been prepared by using emulsion polymerization of polyacrylic acid (PAA) functionalized polystyrene(PS) followed by the sol–gel process. The effect of this special morphology on superinsulating properties of hollow silica nanospheres analyze by using comparison of its thermal properties with ordinary hollow silica nanospheres.The size of the PS templates and shell thickness could easily be controlled by adjusting the AA/styrene weight ratio and tetraethyl orthosilicate (TEOS ) concentration as silica precursor, respectively. Hollow Silica Nanospheres with raspberry-like morphology show a significant reduction on thermal conductivity about 0.02 W/(mK) compared to the bulk value, indicating clearly a prominent size-dependent thermal conductivity at nanoscale.