Calcium sodium aluminosilicate (CaNaAlSi 2 O 7 ) ceramic powder was prepared from eggshells as a raw material via the sol-gel process at room temperature. The CaNaAlSi 2 O 7 ceramic particles were embedded as a dispersed phase in the polyurethane (PU) foam matrix via a direct foaming process. The calcium sodium aluminosilicate (CaNaAlSi 2 O 7 ) ceramic powder had a high specific surface area of 38.89 m 2 g −1 , and a fine average particle size of 13.27 μm, whereas the PU foam had a low specific surface area of 1.00 m 2 g −1 , and of light weight. After adding 10 vol% CaNaAlSi 2 O 7 to the PU, the composite foams possessed a high specific surface area of 6.0 m 2 g −1 , a bulk density of 0.213 ± 0.012 g cm −3 , a high decomposition temperature of 790 °C, and a high compressive Young's modulus of 346.0 ± 76.5 kPa. The CaNaAlSi 2 O 7 /PU composite foams provided good thermal conductivity, uniform pore size and particle size distribution, good bridge bonding, and with microcellular interconnecting cells. The CaNaAlSi 2 O 7 / PU semi-rigid composite foams are potential candidate materials for a variety of products such as construction materials, catalysts, insulation materials, and adsorbent materials. There are several advantages of the semi-rigid composite foams: light weight, high specific surface area, and high thermal decomposition temperature.