This idea refers to a revolving door how reduces energy lost through her using a simple fan.
This idea works on door with four compartments, and functions as it folows: The door have one compartment above the door (A) where is engine, and second compartment is under the floor (B).
The roof and the floor have holls on the left side and on the right side. The door ratates to the right, in the winter for example , on the left side hot air goes out and on the right cold air goes inside. If we put a fan (1) up to push through chamber (A) air from the left compartment that goes out, to right compartment that goes inside, and air from right take him place pasing through chamber (B), we will have a small air exchange between interior and exterior.
Is very easy to manufacture, they need small changes to a conventional door but have a big impact.