Purpose Lightweight insulators are of major importance for the industry, in particular for thermal insulation in buildings. The purpose of this paper is to present a low-cost method to obtain aerogels with high insulating properties. Design/methodology/approach Silica aerogel structures have been obtained by a low-cost sol-gel synthesis method. Surface modification, using dimethyldichlorosilane and trimethylchlorosilane, has been applied in order to get different thermal and optical properties. Findings The samples show very promising thermal properties as tested through an infrared camera observation. A 5-mm-thick piece of aerogel is able to withstand the temperature of a brazing flame and reduce the heat by at least 150 degrees on its opposite side. The samples have a vitreous like structure as observed by SEM, some surface cracking is observed but they stay within acceptable limits. Originality/value A very good thermal insulator is obtained with a very simple and low-cost method. The bulkiness of the supercritical drying is eliminated and the obtained structure has good properties.