Cold AIR permeates. That is correct. But there is no physical concept of COLD. The physical concept that exists is heat energy. Temperature is defined as the am

Cold AIR permeates. That is correct. But there is no physical concept of COLD. The physical concept that exists is heat energy. Temperature is defined as the amount of heat energy per unit of matter. When something gets colder the physical process happening is that heat energy is leaving the thing and being transferred somewhere else/being converted to another form of energy. So when cold air comes into a house heat energy is transferred from e.g. the material that makes up the wall into the air warming the air and cooling the walls. The cold air is replacing warm air which moves out of the building.