Abstract: An apparatus to circulate and regulate the flow of cold air from the exterior of a building having a cold room to the cold room to supplement the refrigeration of the cold room provided by the usual refrigeration equipment. Duct work is provided to carry cool air from the exterior of the building to the cold room, and further duct work is provided to exhaust air from the cold room. One or more blowers operate in conjunction with the duct work to circulate the air through the duct work and through the cold room. The blowers are controlled by temperature controls such that the apparatus can operate only when the temperature outside is below a high temperature limit, and does operate when the temperature in the cold room approaches or exceeds an upper temperature boundary to introduce cold air into the room until a lower temperature boundary is reached.