In too many American cities, numerous downtown office buildings sit barely used, their absence of workers gutting nearby businesses. Meanwhile, hundreds of residents, too poor to afford shelter, sleep on the streets. Addressing these problems is within our grasp.

We can start by getting rid of local rules that require that apartment windows can be opened.

Think about it. When was the last time you opened a window in an office high-rise? Or in a big city hotel room? This rule, made before the invention of air-conditioning and mechanical ventilation, serves little practical purpose today. An open window may be pleasant in the right weather, yet it is also one of the biggest barriers to addressing some of our nation’s most serious problems: housing affordability, homelessness and struggling city downtowns.

I recently co-wrote research at the Pew Charitable Trusts in conjunction with the global architectural firm Gensler that found that dispensing with this rule makes it financially feasible in some cities to build a new form of affordable housing: college-dorm-style single-room units, each with its own window, closet, fridge and microwave, with shared spaces within the center of each floor for cooking, bathrooms, laundry and socializing.

This model, which reflects the fact that office buildings tend to have plumbing buried within their cores, can fit about three times as many apartments on each floor as a conventional design and shaves 25 percent to 35 percent off construction costs. Most importantly, developers could charge $750 a month in Minneapolis, $850 in Denver and $1,000 in Seattle — rents that are about half those for median-priced apartments in typical buildings in those cities, and thus within reach for residents earning 30 percent to 50 percent of the median income in those areas. And for those in need of subsidized housing, this model makes far better use of government money: The $300,000 subsidy that builds a single low-income Denver studio could instead create 13 of these units there.

The benefits for cities and for society at large would be substantial: fewer people living on the streets, revitalized downtowns, walkable access to jobs and transit and a sense of community for residents. Each floor of the building would be secured with key-card access and become a small neighborhood. Institutions such as hospitals, universities and cities looking for supportive housing could rent an entire floor.

By supporting a variety of residents of differing ages and income levels — new arrivals to a city, seniors, young professionals, people who need affordable housing — these developments could avoid the problems that previously plagued public housing. Usually built far from job centers, prior developments concentrated poverty by only allowing residents with very low incomes — problems that factored into today’s housing woes.

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