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Comment by ajross | Hacker News Reader

FWIW: a few high-rise apartment buildings would do far more for climate impact than all the trees they could possibly squeeze into Paris. Paris's building codes have historically been a disaster for density, and at the end of the day it's urban density that matters more than anything else. Get/keep the people off then land, then turn it into something less impactful.

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Paris is one of the densest modern European cities I have ever lived in. My first flat was a 20sqm studio. And my last apartment was 97sqm for a family of 4. Even in NYC the smallest place I could find was 45sqm and even that was considered less than ideal.

It costs a lot of fuel to keep a large apartment comfortable. So your typical American, 800sqft, 1/1 simply would not work in Paris. Micro-apartments are just becoming a thing in the US and even then there is a lot of pushback from inhabitants and developers.

Finally, Paris sits in a valley. The trees aren't just an aesthetic, they help keep the inhabitants sane and clear the air. New York City on the other hand turns into a miserable, swamp during the summer. It's hot, humid, and with no breeze the air actually feels gross.

That’s because NYC itself gets hotter than Paris. Paris isn’t very breezy at ground level because the streets are all short and keep turning. The air stays stagnant, unlike NYC’s grids.

Paris’ density is from the lack of building: instead units just get sub divided ad finitum, instead of building up. Still, density isn’t high, it just feels that way, especially with Paris proper's small size: not even 2 Manhattans.

Then you have larger units 95% unoccupied kept as pied-a-terres/investments.

Those Haussmann buildings don’t do a good job of insulating or HVAC. Even 1970s multiunit buildings in the burbs are all single-pane windows with cracks to the outside.

When you have a weak radiator-based central heating system, you don’t dare turn it down or off when you leave: your unit may never recover and be warm again.

Meanwhile in North America, I turn off HVAC whenever I leave for a few hours: I know it can get back to human temperatures quickly.

Though the French do a good job in summer: every window has shutters, so you can block out the sun very well.

Some of my darkest days have been in Paris in summer because my hosts kept the indoors in total darkness :)

Let's put some numbers. Paris has almost double the density then New York (20000/km2 Vs 10700/km2)

Source: Wikipedia

Paris proper: 104km2. Density: 21.5k/km2

Manhattan: 60km2. Density: 26k/km2, and that's with a bias toward commercial buildings.

NYC: 783km2. Density 10.7k/km2.

Compare apples to apples please.

You're right, that wasn't a good comparison. Still, you have 21.5 vs 26 in Manhattan, saying "Paris' density isn't high, just build more skyscrapers" isn't really reasonable IMO.

Also Paris is small but it's not like it's rolling fields as soon as you cross the Périphérique. Many of the suburbs have densities as high, and sometimes higher, than the capital itself. I wish I could compare the densities of NYC and Paris+suburbs but I can't find the numbers for that. All I could find was a density of ~1k/km2 for the entire région but that's 12000km2 so it's not a very good "apples to apples" comparison.

Paris has 2 large central parks, Vincennes and Boulogne, that are part of the city. 8.45km^2 10km^2.

Paris is 84.45 km² if you remove woods that are outside "Boulevard Périphérique"

Wikipedia wrong by any meaningful mesasure

Most of NYC is 30000/km2 to 20000/km2

https://www.citylab.com/equity/2012/10/americas-truly-denses...

Also

https://urbantoronto.ca/forum/threads/weighted-density-of-eu...

Also

http://www.citymayors.com/statistics/largest-cities-density-... (this one puts Paris pretty far down but as Hong Kong is not on the list it's pretty suspect)

Also see animation showing Hong Kong density dwarfs cities like even Manilla and Mumbai which are clearly much much more dense than Paris

https://doodles.mountainmath.ca/blog/2019/04/24/population-w...

Try looking at Manhattan to Paris for a better comparison

Manhattan - 33.58 mi2 (87km2) - 72,918/mi2 (28,154/km2)

Paris - 40.7 mi2 (105.4km2)

Meanwhile the five boroughs are 468.484 mi2 (1213.7km2), so literally an order of magnitude larger than Paris as a whole.

Paris is less dense now than it was last century. Owners would buy 2 adjacent flats and knock down the walls between. In fact, that is going on now. Friends of ours converted 2 apartments to a duplex (French: an apartment on 2 floors, English: 2 units in 1 building).

Those Haussmanns (actually Belle Epoch, most visitors would not recognize an Haussmann) are quite average in efficiency (~C) if they have been maintained and had the glass replaced in the last 20 years.

Those same Haussmans are individually heated. Only the modern apartments (60s,70s,80s) have central heating. And they almost all radiators have a mechanical thermostat. So I'm not sure what you mean by turning it off. The building guardian will turn on the central heat and then it's up to you to find a comfortable temperature.

> Some of my darkest days have been in Paris in summer because my hosts kept the indoors in total darkness :)

Ahh, here we agree. My last flat we left the shutters closed until sunset. Then when we did open them the music, wine, and cigarettes came out :-)

Maybe we have a difference in terminology? By central heating, I mean a boiler for the building, not district heating. Are those 'Haussmanns' running electric heaters, (maybe mini-split systems nowadays), or fitting a ?gaz? ?oil? burner in a closet for heat?

My experience was that the radiators could maintain a temperature (with some prayer), but don't pump out a lot of heat. I still disdain the mechanical thermostats: you have to turn them up and down as the outside temperatures/sun/winds change.

It didn't help that my hosts put things in front of the radiators, preventing them from radiating.

> Then when we did open them the music, wine, and cigarettes came out

That didn't stop my hosts!

One gas burner per flat, yes.

Central heating was more common in buildings built in the 50s-80s. The only places I know of with district heating are university and government campuses. It was popular then because it was more efficient than wood burning fireplaces. But has since been replaced with in-unit gas boilers.

Our apartment, a 60s era building, had central heating. It put out plenty of heat. I would say far too much heat. We ran into the problem that central heating isn't distributed evenly. Some apartments get lots of heat and some get far too little. Apartments at the top and near the bottom floors were the worst. We've actually had to crack the windows during the winter or we would have roasted.

> It didn't help that my hosts put things in front of the radiators,

I assume they were using them to dry clothes? If that is the case we are also guilty of this as well. Clothes dryers still aren't common in the city. It appears the problem wasn't central heating but your hosts.

Radiators don't pump out heat they radiate it. I would bet the building pipes weren't being maintained nor were the radiators. Paris water is really hard. If you don't descale them regularly the pipes will get blocked with lime. And it is really evident when water comes out in a trickle.

Not clothes, but putting a board on top to store things, or a couch next to it against the wall. Drove me bonkers.

At least I would aim a fan at it to actually heat a room.

Then those people move to North America and set the thermostat to 29C thinking it’ll make it warmer faster. It won’t.

>Still, density isn’t high, it just feels that way

That's factually incorrect. And even assuming that it isn't how do you propose to deal with even more people in the capital when all the streets are gridlocked at rush hour and the public transportation is more than saturated? Are you seriously proposing that we raze the city and rebuild it New York style? I mean I suppose Haussmann sort of did that but I think it would be quite a loss to do it again now.

I think it's much better to work on decentralization and developing other French cities. We're not Singapore, Monaco or Honk Kong, we don't need to fit everybody in the same metropolis.

>Paris isn’t very breezy at ground level because the streets are all short and keep turning.

I don't even feel like digging into this frankly absurd take (and again, are you proposing that we simply rebuild the city as a grid?) but it's also clearly not the only factor at play. Yew York is near the ocean, meanwhile Paris is in an inland basin which usually gets very little wind. Maybe very high rises could get above the smog at the top levels but would that really solve the problem?

>Those Haussmann buildings don’t do a good job of insulating or HVAC. Even 1970s multiunit buildings in the burbs are all single-pane windows with cracks to the outside.

>When you have a weak radiator-based central heating system, you don’t dare turn it down or off when you leave: your unit may never recover and be warm again.

That much is true, many buildings in Paris are very old and have terrible isolation (on every level).

> And even assuming that it isn't how do you propose to deal with even more people in the capital when all the streets are gridlocked at rush hour and the public transportation is more than saturated?

Maybe the metro/RER is saturated at rush hour, but I can assure you there is plenty of capacity left when you look at the whole picture. And you can always run more buses and create an environment that makes them fast through signal pre-emption, bus-only lanes/roads/hours, frequent runs, express buses, etc. A bus system can never be saturated unless they're running bumper to bumper.

And work on the demand side: Work-From-Home, compressed work weeks, staggered schedules and not forcing people to take vacation in the same month.

If you won't change supply, the goal should be to reduce transit demand, not increase it.

Finally, tabulate how much a new metro line costs. Send inspectors to every workplace with more than X employees. If it appears that any of the above could be done but isn't, send them a bill for their proportionate costs for a new metro line.

Could also send bills to employers for each employee-day they compel to arrive between 8 and 9. And/or give a discount to businesses that don't. You could achieve similar with dynamic pricing.

>Paris isn’t very breezy at ground level because the streets are all short and keep turning.

> I don't even feel like digging into this frankly absurd take.

Microclimates are a thing. If you're ever in NYC/Boston/$NE_City/Toronto/Montreal in January/February, you won't forget arctic winds compressed through small passages.

>> Still, density isn’t high, it just feels that way

> That's factually incorrect.

I'm not sure that be stated as factually anything without an accepted definition of "high density" for a city. I'm not aware of one.

Having more Montparnasse-esque towers would destroy the a lot of the streetscapes created by Haussmann that make Paris so distinctive. How can you not love all of the chimney pots?

Keep the height restrictions inside of the city and continue to keep high rises near La Défense and serve them with efficient and effective mass transit.

Agree. For some reason many people either dismiss or undervalue the character of cities and neighborhoods, which are a critical part of their culture, the quality of life, and what made them attractive in the first place.

That’s an odd take. Paris is the densest city in the EU and one of the densest cities in the world.

That's arguable one of those lies of statistics. This comes up every time for example Hong Kong is way way WAY more dense than Paris. But because of arbitrary city boundries some unpopulated mountains are included in the city borders so the true density is not remotely the density listed on these kinds of lists.

Go visit Hong Kong and you'll see it's easily 5x as dense as Paris. Maybe more. The same is true of many other cities in Asia. Visit and you'll realize the stats that show Paris in the top 10 are complete BS.

The same thing comes up NYC vs LA. By the land / people they are about the same density but anyone who's been to both knows NYC is more dense than LA. Using population weight density shows NYC is up to 3x more dense than LA

https://www.smartcitiesdive.com/ex/sustainablecitiescollecti...

With poulation weighted density Paris is not #1 in Europe

https://urbantoronto.ca/forum/threads/weighted-density-of-eu...

And if the same was applied world wide Paris would not even be in the top 100

It's also tiny. It's easy to win the "densest city" contest when you exclude the decreasingly dense outer areas.

https://en.wikipedia.org/wiki/List_of_European_Union_cities_...

The trees are not there to prevent climate change by absorbing CO2, but to mitigate the effects of climate change by providing a cooling effect through shade and water evaporation.

Reducing car traffic also helps to improve the "climate" of the city on a hot day.

Paris is pretty dense already ! In the top 10 cities : https://www.worldatlas.com/articles/the-world-s-most-densely...

High towers cannot be put everywhere

> High towers cannot be put everywhere

Why not?

The ground. Paris's ground is not strong enough to support high rise building especially in the southern part, where a lot of it have been excavated in the last 500 years (and filled with dead bodies, ie the catacombs). Of course with clever engineering everything is possible, but that really limits the development of such towers.

It is true that the main limitation still is the construction code, which preserves the global proportion of the city.

The usual approach is to punch pilings into bedrock. Nothing new really. Hollow shafts might be an issue, but nothing a stroke of the pen won't solve.

Gets a lot more complicated when you have tunnels everywhere already.

That’s what I meant by shafts. You could fill them, but dunno how kosher that is. It’s not like they’re open to the public or anything.

I believe you can take the catacombs under Montparnasse station, so it’s a solved problem ( I hope ).

I'm not at all sure what you mean. There is no way you could fill the catacombs, if that's what you're suggesting. And how does having catacombs under montparnasse show that you can put pilings through train tunnels?

Because they worsen traffic, as they create high density traffic zones which then need to have bigger highways around it, then you have got the fact that Paris's low city profile is a monument on itself, so city administrators don't want to disturb that too much, then there's the issue of physical construction of em as paris is a river bank city, quite sandy ground iirc

Paris does have areas which have high rise office buildings tho, it is just not the zones people know much about because they are not the touristic areas

Hong Kong seems to be able to make tall buildings work, with as massively increased density, in comparison to paris.

> Paris does have areas which have high rise office buildings tho

Then maybe more buildings should be built in this area.

a lot of parisians like me find them very ugly and there's already not enough garden and green spaces to out to.

Paris is one of the densest city in the whole world.

In many large cities you see sprawling suburbs and neighborhoods with individual houses. These take up a huge area that could have been planted with trees, need a lot of new infrastructure built (a lot of asphalt), and a lot of brand new lawns to water. All of which have plenty of negative environmental impact. This also encourages people to go for personal cars since public transport never really seems to keep up efficiently given the low density and large areas. And all of those cars go to the city every day.

The problem is basically everyone thinks the solution to all of this is to buy an EV (I know I'll get a lot of hate from EV owners/fans for this one; still true for those who fit the rest of the description above) instead of seeing all the other ways with far bigger impact. Like not needing a car at all, for one. This would slowly reduce traffic to the point where cutting a lane doesn't cause any severe inconvenience.

I have family in the Paris suburbs: they never have to water the lawn, there is enough rain for that. Trey also don't have a lot of asphalt, there are some narrow streets connecting village to village and even smaller streets in the villages. There are lots of trees everywhere, it's as green as you can get.

What I described is a general problem around most if not all big cities. This is a random internet picture from a Paris suburb (close to CDG) [0]. While there are some trees it's far from a forested area. A green lawn is a far cry from a green forest when talking climate. And any unnecessary asphalt is too much. Just browse around with satellite view if you're curious how such villages look like compared to the actual patches of forest. This is a village ~25Km from Paris, right next to a forest [1].

While these low density suburbs definitely provide more comfort for their inhabitants much like cars provide comfort for their drivers, it's a very inefficient use of that land to everyone else's disadvantage and guarantees those people have to drive to the city. Public transport wouldn't be anywhere near as efficient when you start spreading tens of Km from the city in every direction.

And there are far bigger offenders out there like in this random pic. [2]

> they never have to water the lawn

That sounds like an anecdote but I drove through plenty of suburbs (Paris or otherwise) and most lawns were green even after heatwaves and droughts. I'm pretty sure so many still generously water their lawns. Pools just add to that.

[0] https://l7.alamy.com/zooms/cc7447863ce84406b71d51be29c7b830/...

[1] https://www.google.com/maps/place/Maffliers,+France/@49.0754...

[2] http://i.huffpost.com/gen/1291806/images/o-SUBURBS-facebook....

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