An air conditioner is a device that makes the indoor environment of a house or building comfortable. Therefore, it is important to be aware of housing trends and conditions in order to understand air condition- er demand trends. Many books on housing and architecture have been published, focusing on architectural design and floor plans, but there are surprisingly few numbers of books on air conditioning. Where books on housing mention air conditioning, the contents are sketchy. Here, air conditioning from the perspective of housing is described, as well as air conditioning for eco-friendly houses that have been attracting attention in recent years.