Safe, comfortable housing is a key element of a livable community. However, post-World War II housing in the U.S. has tended to favor one prototype above all others: the suburban, single-family home. Yet changing population demographics require the provision of a much broader range of housing types, in order to meet a variety of needs. Since the 1950s the average house size has doubled while the number of people per household has shrunk. Is it any surprise that housing has become less affordable in many parts of the country?
The market for housing is in continual flux due to these demographic changes. For instance, the percentage of older adults in the U.S. population is rising at a very rapid rate; the "Baby Boomer" generation is now entering retirement. The number of Americans 65 years or older is expected to exceed 66 million in 2030, up from 31.8 million in 1991. Many of these "empty nesters" don't need, or want large, isolated suburban homes.
The profile of newly-formed U.S. households is also changing significantly. While the housing industry continues to build homes for young married couples with children, this demographic will comprise fewer than 10 percent of the new households formed between 2000 and 2015 (Slevin 2005).
At the same time, the emphasis on low-density suburban development has priced many young people out of the housing market. The cost of owning a single-family home has soared in many places, forcing many young people to delay or abandon efforts to purchase a home. While 44 percent of households could afford to buy an entry-level home in California in 2008, this figure drops to 30 percent in the San Francisco Bay Area and 29 percent in Monterey (CA Association of Realtors 2008). The construction of affordable housing will continue to be a crucial activity, and a great challenge, in the coming decades.
For these reasons, more people are considering or will need to consider more resource-efficient, compact housing. Compact residential development is not only less expensive, but also benefits communities by reducing vehicle trips, encouraging bicycling and walking, and supporting public transit. A 1990 survey by the Sierra Club's John Holtzclaw, found that residential density is the "most effective urban variable in predicting auto ownership and driving." For every doubling of neighborhood density, vehicle miles traveled (VMT) are reduced by 20-30%. When people live at higher densities, they are more likely to walk for travel, shop locally, and get to know their neighbors, fostering a sense of community and creating safer neighborhoods.
In many cities across the country, an increasing number of single individuals and families are beginning to trade in the suburban lifestyle for the benefits of affordable housing, compact urban development, and a lively urban experience.
Second units (also known as accessory units or "granny flats") are another means of achieving more compact development and providing affordable housing. Second units can be built in backyards or above garages and can be rented to students, elderly people or single individuals. An accessory unit provides additional income to the homeowner and can help pay their mortgage.