A flame resistant electrical insulating material comprises glass fibers, a particulate filler mixture, and an inorganic binder, wherein the electrical insulating material has a UL-94 flammability rating of V-0, 5VA and a thermal conductivity of less than 0.15 W/m-K. The particulate filler mixture comprises at least two particulate filler materials selected from the list of glass bubbles, kaolin clay, talc, mica, calcium carbonate, and alumina trihydrate. In an exemplary aspect, the insulating material is not punctured after direct exposure to 2054° C. (3730° F.) flame for at least 10 minutes.