To provide a dual air circulation system and a 24-hour ventilation system which are the basis of performing whole building air-conditioning of a building such as a house friendly to both people and the building.

The building is constructed of a highly heat insulating and highly airtight structure 10 around the peripheries of a foundation part, an external wall part and a roof part. Air-circulating communicating lines 59 are formed to serve for communication between an underfloor concrete foundation internal space part 53 and an attic space part 54 through clearance parts 51 between external wall members surrounding and covering the building, and internal wall members surrounding and covering all living room space parts, clearance parts 52 between columns and interior members surrounding and covering the columns, or the like, and a circulating blower 21 is disposed to form a first system. A second living room internal air circulating blower 22 is mounted into a living room internal blowing passage 31, and the flow of circulating air can be reversed in the summertime and wintertime while causing no temperature difference between an upper story floor part and a lower story floor part to form a second system. A third air supply blower 23 for 24-hour ventilation is disposed to supply air to all the living room space parts. Room pressure is thereby kept constantly positive, and air can be exhausted only by differential pressure.