PURPOSE: To increase the capability of a passive air cycle by arranging latent heat accumulators in the structure such as inside spaces of roof trusses, underfloors, internal walls and partition walls, substrate materials, ventilation layers, etc. of a building.

CONSTITUTION: Latent heat accumulators A1, A1 are arranged in the structure such as the inside of a roof truss space 6, an underfloor space 5, an internal wall cavity 3, and a partition wall cavity 4 of a passive air cycle house. And also, when required, latent heat accumulators A2, A2 are arranged in the substrate members surrounding the room like the substrates of walls, floors and ceilings. And further if necessary, latent heat accumulators A3 are arranged in a ventilation wall layer 2-2 and a ventilation roof layer 2-1. And heat is accumulated during the high temperature time like day time and discharged during the low temperature time like night time. In this way, the inside of the room can be kept always comfortable.