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Comment by Kalium | Hacker News Reader

> Isn't it a slippery slope though?? You have to just keep adding supply but unfortunately the amount of living space that can be built in an urban area is constrained at some point both vertically and horizontally.

You're absolutely right. There's definitely real limits, vertically and horizontally, to how much density is physically possible.

As an upper limit, we have good historical examples density of around 1.2 million people per square kilometer being workable. I don't think any part of the US today comes close to that - what data I can find says that the most densely populated part of the US is at 66,000 people per square km. That's multiple orders of magnitude different.

With that in mind, I think it's possible that we haven't yet hit any real physical or space-based limits in American cities. Only political ones.

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Why force people to cram into the miserable conditions of 1.2 million people per kilometer to get a good job?

You're right, forcing people everyone shoulder the financial burden of maintaining a motor vehicle, forcing them to engage in one of the most dangerous activities humans can engage in and forcing every possible place they might want to visit to have a spare 158sqft is much better.

There is a happy medium here...

I'm as density-friendly as it comes, but I think that we'd be much better off at maximum 20,000/sq km or so.

(That's not a magic number - that's about the density of the city of Paris, ignoring inner ring and outer ring. That's average across Paris, mind you, not some absolute maximum.)

Oakland is 3,000ish per sq km, for reference. Now, I'd prefer that we don't have to live in the 400 sq ft/40 sq meters kind of options that are older Parisian apartments, and I think that proper sound insulation is ground stakes (which current 5 over 1s in America don't do a great job with) but I think we can make the argument of more density without pushing for the extreme argument here.

It'd be amazing if we got to Paris style density in half of the top 20 cities in the US. I just haven't seen great ideas or plans to transform the heavily car dependent sun belt cities into denser places.

Maybe but you’ve gotta consider that a lot of people want to live in say Denver or Dallas because they aren’t dense. If I wanted a New York City or San Francisco type of lifestyle I’d move to one of those places. If the demand was there, less dense places will become more dense naturally without ideas or schemes to force it.

Soundproofing hasn't historically been a part of US building codes is why it's not done here. California added an optional Soundproofing part of the code but cities must opt into it. Oakland is actually one of the few cities in California which has.

Because people want to cram there?

I do agree that decentralizing the jobs is a really good thing. But while people want to cram into the same area, the government should not fight them.

Because dense, urban areas are the most environmentally friendly places humans can live, for one.

There's a density limit on carbon neutral housing, you can't scale vertically and lower carbon impact. IIRC it's something like after 3 stories you need to scale horizontally for solar power to offset the carbon impacts of powering the pumps for water/sewage, elevators, and additional concrete required for foundations.

So it's not necessarily dense that's the most environmentally friendly.

Thing is, North American cities are so spread out that even 3 stories would be close to an order of magnitude of improvement.

Imagine if no zoning code could prevent a developer from creating up to 3 story, multi-unit buildings on standard quarter acre lots. Just that alone would more than double the density in the United States overtime and still give most people PLENTY of space before we even have to start making sacrifices

You have to account for the cost of transportation as well, though. The more density you have, the more you will be able to walk to most destinations and the more cost-effective public transport gets.

Sure, but what I'm saying is that it's not as simple as a function that moving people closer together is infinitely scalable to lessen our impact on the environment. There's no free lunch.

That's why I think upzoning to medium density 15-minute cities is the best of both worlds.

Not to mention that living in a dense urban environment has a worse quality of life for a lot of people - that's why people don't want to do it. They like the space.

not that i disagree, but could you elaborate on that please?

as one commenter suggested, the problem is that job locations are too concentrated. we have already proven that remote work is effective, so there is no need for that any more, and super high density is not necessary.

the environmental issue with low density is mostly cars, which can be solved with good public transport, which btw will also be needed in super high density areas because people will also want to go out of the city some times. i also believe that environmental friendly construction affects the possible density a city can have. concrete is not exactly environmental friendly material. (for high density steel without concrete would be better, it's more lightweight too, so allows for higher buildings)

in short, there are a lot of factors that go into environmental friendly living. what are the factors that favor high density?

This paper goes into great detail about how urban households have lower emissions than suburban ones.[0] This is made up of the different energy, transportation, food, goods, and services emissions of the different lifestyles associated with each area. For instance, going beyond transportation, climate control for buildings is one of the top uses of energy. Detached single-family homes are pretty must worst case, compared to attached housing, or even multi-story apartments, etc.

[0] https://pubs.acs.org/doi/abs/10.1021/es4034364

climate control

good point.

i live in an area where climate control is not needed at all, so that changes the equation considerably here.

A few reasons, off the top of my head:

First, only some jobs can be done efficiently in a remote way. We should not be in a rush to generalize this to every job.

Second, public transit can be more energy and cost-efficient when in a denser context. In addition to public transit, there's also cargo transport for things like food, which given dense areas can be handled by more carbon efficient methods like water and rail instead of trucks. We haven't even touched on the efficiencies for water, sewer, and electrical infrastructure.

Third, dense construction can be done with timber. We've now reached a point technologically where a 100m building can be constructed primarily out of wood (search "plyscraper"). Wood is a very ecologically friendly material, as using it means capturing carbon.

Fourth and finally, building up instead of sprawling out means less deforestation, less draining wetlands, and less paving over prairies.

In short there are a lot of factors that go into environmentally friendly living, and most of them favor higher density.

cargo transport for things like food, which given dense areas can be handled by more carbon efficient methods like water and rail

i am skeptical about that. at least with the existing huge high density cities like those in china. less density (well, actually small islands of high density, in relation to your point four) would allow space for local food production. and truck vs train is not a factor of distance. if anything longer distances are more efficient by train and water whereas the last mile likely will remain with trucks (which could be electric though)

i agree with the other points, and i wasn't aware that wood construction went that far already.

capturing carbon

coincidentally i was just listening to a german audiodrama about capturing carbon.

> environmental issue with low density is mostly cars

Suburban houses require more resources and energy to build, maintain, heat/cool. Transport is just a small part of it.

Where did they have "1.2 million people per square kilometer"?

https://en.wikipedia.org/wiki/List_of_world_cities_by_popula... only goes up to about 80 thousand ... and the city with the highest population density in that list is one I must admit I'd never heard of, so there's a pub trivia question, perhaps.

It's hardly a shining example of livability, but the former Kowloon Walled City purportedly had a population density of over 1.9 million/km2. [0]

More realistically, we can see examples of nice residential neighborhoods in Washington DC ranging from 30,000-100,000+/km2. [1]

[0] https://en.wikipedia.org/wiki/Kowloon_Walled_City

[1] https://ggwash.org/view/42469/what-do-80000-people-in-a-squa...

According to this youtube video [1], some city blocks in Manhatten can reach up to 280k/km2

[1] https://youtu.be/y3XoUBzfXps?t=453

And DC has wide streets & building height limits!

Kowloon Walled City made it to 1.9 million people per km².

Your list of cities misses this because it's comparing entire metropolitan regions (not clear how this is precisely defined), as opposed to neighborhood-level densities, which is where you can get the hundreds of thousands or millions of people per km².

It housed 33,000 people. While on paper that's extremely dense it's not necessarily scalable - and kind of provably so, since they tore it down and evacuated everyone who lived there.

What would the sewage infrastructure look like for a 1km square with almost two million people in it? How about the ventilation? Police and fire? It's not really tenable.

Tore it down against the will of the people living there. And the building height was constrained by an overhead airport approach. KWC could have been even denser. I don't think going full KWC density is a good idea, but comparisons to it serves as a rough measure of how far from "full" a city really is. And I think it's important to remind ourselves of that from time to time.

SF, to pick an example near and dear to HN readers, is not full. All residents of the Bay Area could fit between Market Street and Van Ness Avenue with lots of room to spare.

That kind of density requires trains. However, thanks to the privatisation of every aspect of our society, we can't build trains anymore.

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