A curable coating composition for forming a thermal insulating layer, the composition comprising: (a) highly porous particles of a material obtained by drying a wet sol-gel, the particles having a porosity of at least 80% and a particle size in the range from 5 .mu.m to 4.0 mm; and (b) a film forming resin system comprising a film forming polymer, wherein the particles (a) are dispersed in the resin system (b), and the resin system (b) contains at least one stabilizer having an average molecular weight in the range from about 1,000 to about 4,000, said stabilizer being at least one member selected from the group consisting of ethylene oxide-propylene oxide block copolymers, poly C.sub.2 C3 alkoxylated C.sub.12 C.sub.18 saturated or unsaturated fatty alcohols, poly C.sub.2 C3 alkoxylated hydrogenated or partially hydrogenated castor oils, poly C.sub.2 C3 alkoxylated hydrogenated or partially hydrogenated soybean oils, polydimethyl siloxane C.sub.2 C3 alkoxylates, and sorbitan esters of C.sub.12 C.sub.18 saturated or unsaturated fatty acids, the amount of the particles (a) is in the range from 2 to 6% by weight, based on the weight of the composition, and the amount of the stabilizer is in the range from about 50% to about 90% by weight, based on the weight of the highly porous particles. The composition has high storage stability and forms a coating having excellent insulation value.