Micro apartments are the future, encouraging their inhabitants to buy less, use fewer resources, and live in a more streamlined, minimal way. Which is exactly why they were featured in both last and this month’s Metropolis (It’s a Small World); they presage new ways for us to live, and the concurrent design challenges inherent to them. While tiny apartments aren’t exactly news in some urban areas, the newest versions clock in at anywhere from 140 square feet (Microsoft-adjacent apodments in Redmond, Washington) to a more typical 420 square feet, (recently approved in San Francisco) to 370 square feet (largest micro apartments in NYC).

But what about REALLY micro apartments?

In Hong Kong, one of the most densely populated cities in the world (with rents some 35% higher than in New York City) about 100,000 people, including families, live 40 square-foot spaces (I don’t think most of us would qualify them as ‘apartments’), as depicted in these arresting photographs from the city’s Society for Community Organization (above and below):

Most of us, no matter where we live, will question if those spaces are big enough for one person, let alone a family. But it definitely begs the question, how small is “too small”? How do we arrive at the minimum sizes for a dwelling?  A confab among city planners, designers, potential residents and maybe even sociologists or anthropologists is needed here.

In New York City, as in most cities, the minimum apartment size was set by zoning laws. In 1987, the smallest a new apartment could be was set at 400 square feet (older, smaller places were grandfathered in). For mayor Bloomberg to introduce the small apartment plans that he did, he had to get special zoning permissions. The same is true for San Francisco, Philadelphia, Redmond, Washington and other cities with micro spaces; they have to be designed and sold as a specific type of dwelling to meet a specific need. Indeed, as the original article points out, most of them have space-saving built-in appliances and closets, and often, high ceilings, so space is utilized intelligently and encourages openness and comfort. They aren’t just small, but smartly so.

Ultimately, it’s the designers who determined these apartments’ sizes (which were then approved and vetted by public housing officials and the public, during exhibitions and competitions for the best design). They are, truly, crowd sourced apartments, both in size and layout. But why not let the market determine the apartment sizes?

This seems like it might work until you read through the comments on many of these micro apartment stories online. What one person calls a micro-apartment, another calls a tenement. But tenements were about small spaces being used to house families (closer to the Hong Kong examples, above), and a large proportion of city dwellers no longer live in a family unit; in NYC in 2009, 33% of people lived in their apartments alone, and 17% contained couples sans kids – but yet there’s a glut of 2- and 3-bedroom apartments for family units. All those singles and couples desperately need smaller (read: more affordable, and more suited to their lifestyles) places, but there are only 100,000 studios and one-bedrooms available in NYC—their scarcity then drives their prices higher than they should be.

As Jerilyn Perine, executive director of the Citizens Housing and Planning Council told channel Thirteen’s Metrofocus, “The housing market can’t possibly keep up with the population growth we’re projecting. This idea that adding to the housing supply by continually adding housing for families doesn’t address the underlying needs. This need is increasingly finding its way onto the underground housing market.”

Micro apartments offer a solution to the problem. But the majority of people will always want more space (see the upsetting New York Times article about elderly folks living in large, subsidized apartments, refusing to give them up). And for many, living in a small space is a question of prior experience. If you grew up in a suburban house, a micro apartment can seem “too small.” But for someone who has lived in a studio for years, it might seem plenty large enough (and some people, as in the Hong Kong example, are willing and able to live in too-small spaces if they aren’t regulated away from that). So maybe designers and city planners are the best final arbiters on apartment size, since it seems that other approaches, like letting developers or renters themselves decide, has so far resulted in ineffective solutions.

Starre Vartan is an author, journalist, and artist whose work concentrates on sustainability in consumer products, including a focus on vernacular, nature-based, and eco design. Recognized as a green living expert, she is the publisher of Eco-chick.com, a columnist at MNN.com, and contributes to Inhabitat and The Huffington Post. She is Metropolis’s copyeditor.