In buildings located in the northern and central sections of the United States, where low winter temperatures are common, an attempt to maintain a winter relative humidity of 55 per cent may result in serious harm to the structure. In addition to condensation on windows and walls, the migration of water vapor to surfaces where it will freeze may result in serious masonry cracks. A solution to this problem is a building within a building , constructed, perhaps, in interior storage areas which are completely surrounded by other rooms, and which have no walls or ceilings in contact with the outside of the structure. Provided with a natural variable humidity level so that no damage occurs to the building in cold weather, the perimeter area is equipped to handle the effects of solar and weather changes, thus making it possible for the isolated area to maintain desired temperature and humidity levels. Detailed information about applying this concept to existing structures as well as to new construction includes control instruments used, heating, ventilating and airconditioning systems. Effects of spot lights and of sudden changes in temperature on the relative humidity of the object are also noted.