A new study looks at what amount of space might be sufficient for American single-family homes:

Social scientists have extensively documented the strategies used over the past century to purposefully upsize the preferences of consumers in high-income countries (Collins 2000; Nickles 2002; Cohen 2003; Horowitz 2004; Clarke 2007; Jacobs 2015). These practices became increasingly prevalent during the years following World War II and have been revamped and augmented to encompass an ever-expanding array of products. The most notable example of this phenomenon – abetted by builders, architects, realtors, mortgage bankers, public-policy makers, and numerous others is housing which in particular has in the United States, Canada, and Australia approximately tripled in size in just a half-century. This process of residential upsizing is understandable as individuals and organizations were for the most part responding to prevalent social and economic incentives and investing a portion of the gains accruing from increasing productivity and rising incomes into more spacious accommodation. While the trend contributed to unambiguous improvements in standards of living, evidence is now emerging that the process of residential upsizing is not contributing to gains in “house satisfaction” (Bellet 2019).

However, the contemporary era, characterized by climate change, economic inequality, and deep social divisions, requires new priorities. Rather than looking to enlargement as a panacea for all manner of problems, the targets outlined in the Paris Agreement and the United Nations 2030 Agenda for Sustainable Development require high-income countries to pursue a sustainable consumption transition. The downscaling of home size, because of the substantial volumes of resources required to meet residential needs, will be a critical part of this undertaking. While the methodology to formulate a minimum social floor and a maximum biophysical ceiling is necessarily provisional, it provides a place from which to begin to consider this important issue.

And from a summary of the article:

In the U.S., average floor space per person would need to be reduced from 754 square feet to 215 square feet, which perhaps surprisingly, is roughly comparable to the amount of space available during the baby boom of the 1950s.

While Cohen acknowledges the myriad political, commercial and cultural challenges of imparting such a sufficiency ceiling on current housing practices, he highlights five examples that he asserts point to shifting sensibilities: the tiny-house movement in the United States; the niche market for substantially smaller houses and apartments in the Nordic countries; the construction of accessory dwelling units in west coast cities of North America; the growing popularity of micro-apartments in New York City and San Francisco; and the emergence of co-living/co-working facilities in Europe.

Four quick thoughts:

1. There are a lot of factors pushing Americans toward bigger houses in recent decades. Pushing against these factors would require a lot of time and energy. For example, reducing consumption might help people think about smaller spaces.
2. Given the local nature of building and real estate, I have a hard time imagining this happening top-down. On the other hand, I could imagine some locales adopting such guidelines and then it spreading to similar locations or even the whole country. At the least, it could be popular in expensive real estate markets – think Bay Area or Seattle – though it would be interesting to see how wealthier homeowners deal with such guidelines. Perhaps if it was instituted for a housing units going forward, there would still be a supply of big homes for those that want them.
3. Related to #2, I would guess more Americans would be motivated to pursue smaller homes because of cost and lifestyle preferences, not because of environmentalism and realizing that single-family homes make significant contributions to carbon emissions and require a lot of resources.
4. How much of this is dependent on building a better public realm? People might be more willing to give up private space if they saw attractive alternatives like coffee shops, libraries, and other public settings where they could live their lives. Americans do not have developed public living spaces or many do not have regular patterns of spending important hours away from their private homes.