In 1951 r. F. Gay patented in the U.S. a system of forced circulation of heated air in all external "shells" of the building, forming a thermal coating (Thermal Envelope). This method, thanks to air ducts, uses the entire building to store heat. The heat heated in the collectors in the southern part is directed through the channels in the ceiling of the last floor to the wires in the northern wall and from there or to the heat storage tanks located under the ground floor, or through the canals in the ground floor ceiling again to the collectors in the southern wall.

The latest way of storage, still in the trial and trial phase, is the use of chemicals, undergoing phase transformations under the influence of increasing the temperature, or synthesis or decay. These materials have many advantages: melting point close to room temperature, high heat capacity in low mass, relative abundance and increasing durability (improved calcium chloride hydroxide — "Chliarolitte" can pass over 6000 Cycles).

The most popular are materials undergoing phase transformations, and among them Glauber salt. They can be used in all passive systems, by supplying solar radiation directly to them, or heat them with warm air. These substances can be incorporated into building materials, in appropriate containers add to building partitions or set up building partitions from self-supporting containers.

However, these substances must not be overheated, because then their efficiency as a heat store will be the same as water. Glauber salt works best at temperatures from 27 up to 38°C. She first used it in the Dover-House building. (UNITED STATES) w 1949 r. M PhD. Talkes. The heat storage contained 13 m3 (21 t) Glauber salt, and solar energy covered 80% heat demand in this building. Certainly, the ways of storing heat using chemicals will be improved and will displace water and stone storage..