On Density
- Posted by ryan on June 25th, 2009 filed in Cities
BeyondDC thinks I think that density and height are synonyms. I don’t. I am able to recognize, however, that the two are related. If you want to add density to an area, you begin by adding people. But you can only add so many people in a given volume before folks start to complain. At some point, it necessarily becomes true that the height limit constrains further increases in density. In parts of the District, that point is right now. One could say that there are tens of square miles in the city in which heights are well below the limit, providing ample opportunity to increase density without doing a thing about the height limit. That fails to recognize that some neighborhoods, by their character, will never be upzoned. Most of Brookland, with its acres of single-family homes, will never be upzoned. Increased density mainly comes from redevelopment of upzone-able land in a few pockets in the city, and in those pockets, the height limit routinely becomes a factor (and will become more of a factor as the number of redevelop-able pockets declines).
BeyondDC’s main arguments against using the two terms somewhat interchangeably are as follows:
- Tall buildings almost always end up wasting vast amounts of space to oversized plazas and setbacks. If one compares aerial images of say, Ballston and Dupont Circle, it is easy to see that even though Ballston is fully urban and “built out” in its center, there are massive gaps in the urban fabric as compared with Dupont. This effect doesn’t stop at plazas; taken to an unfortunately frequent extreme it often results in cities where land owners think nothing of achieving the same density by building twice as tall and leaving half their land for parking. When land isn’t at a premium, there’s no reason to conserve it.
- Tall buildings are difficult to modify. Avent makes the excellent point that it’s counterproductive to prevent large rowhouses from being subdivided into smaller apartments because subdividing them increases the number of units and therefore increases density. He’s right, but that sort of thing is much more difficult and rare at the elevator building scale than at the rowhouse scale, which means that elevator buildings are more likely to keep their original number of units over time rather than increase them. Since large new buildings almost always have to be “luxurious” in order to justify their construction costs, they’re almost always built with a lower number of expansive interior units rather than a higher number of small units. This means that generally speaking, tall buildings have fewer units on a per-square-foot basis than short buildings.
BeyondDC seems to be confusing height with design. I wouldn’t point at the 1950s era monstrosities that characterize parts of downtown Washington as an unfortunate but inevitable consequence of the height limit. They’re an unfortunate consequence of stupid design. There is no reason at all that tall buildings can’t be built well and flexibly. You have but to walk through New York to see that most of the city’s tall buildings waste no space at ground level, and are often switched between uses.
BeyondDC is also making some silly statements about the economics of building tall that just aren’t supportable. Developers try to build tall overwhelmingly because land is at a premium. The gaps in the urban fabric don’t exist because tall buildings have made them value-less; quite the contrary. In most cases developers are working hard to transform them into similarly dense projects.
Large buildings don’t have to be luxurious to justify their construction costs. The tall condo buildings in Ballston are nice enough, but they’re not luxury units. BeyondDC seems to be imagining some bizarre world in which developers build tall and are forced to build luxury complexes to cover their costs, and yet their construction makes the surrounding land extraordinarily cheap. If that were the case, someone in the market for luxury could just buy surrounding land and build something truly luxurious for a pittance. Why buy some expansive condo priced high to cover a builder’s costs when you can pick up the parcel next to it for nothing and build a mansion?
Moreover, it’s irrelevant whether density per square foot is lower in tall buildings if they increase the absolute density of the city, which is what we’re talking about. BDC also seems to be imagining a world where if we were to make the height limit lower still, we’d increase density. That’s obviously not going to be the case.
I know people are sensitive about the height limit, but the fact remains — it prevents people from adding density in very green places. No place in the metropolitan area has the transit coverage of downtown Washington, but it’s simply impossible to increase the density of that area by any appreciable amount, for one reason and one reason only.
June 25th, 2009 at 11:02 am
BeyondDC makes an important point that’s neglected here: infill development of midrises would probably more effectively increase density than replacing existing 10 story office buildings.
For the same reason, I believe modest increases in density in outlying areas may, counterintuitively, have a stronger impact on the region’s density (and thus greenness) than building in the District. This is, to coin a term, because of “decreasing returns to density.”
It works a lot like the “MPG illusion”. Miles per gallon is misleading because fuel efficiency doesn’t really increase linearly. The better measure is gallons consumed per 1000 miles:
It’s the same with density. Like miles per gallon, “people per square mile” is “efficiency per consumed unit” - land in the case of density. But the better measure is “square miles per X people” - how much land do a certain amount of people consume?
DC density is just below 10000 persons/sq mile. Put differently, it takes 1 square mile to house 10000 people. Let’s imagine that a massive new infill highrise development increased that density by 1000, to 11000 persons/sq mi. Then, you’d need 0.91 square miles to house 10000 people, saving about 0.09 square miles of land.
By comparison, the density in Fairfax is about 3400 persons/sq mi. Let’s say you built a dense development on undeveloped land here, increasing density in this case by 500, to 3900/sq mi. Fairfax would go from consuming 2.94 square miles per 10000 people to 2.56 square miles. You’d save 0.38 square miles per 10000 people. The development in Fairfax would, in other words, save 4.2 times the amount of land as the DC development.
The point is that similar absolute increases in density have a much greater impact in low-density areas than high-density ones. Infill on vacant land is much better than replacing shorter buildings with taller ones. And increased density in very low-density areas may actually be better than increased density in already dense locales.
What am I missing?
June 25th, 2009 at 11:07 am
That there are few opportunities in the District to move from low to medium density.
June 25th, 2009 at 11:38 am
Exactly. There are a few opportunities within the District - NoMA, around the Ballpark, RFK and Poplar Point - and that’s about it.
You can’t increase the density AND preserve the residential rowhouse neighborhoods AND keep the height limit.
It’s also worth noting that you could easily add to the height of buildings with setbacks that would allow for the same sun angles to reach the streets - not sure if it would make economic sense to do so, but it can be done.
June 25th, 2009 at 11:42 am
>there are few opportunities in the District to move from low to medium density.
That’s just not true. I listed a whole slew of them in my original post. Yeah, it would be politically difficult to redevelop East Potomac Park, the Pentagon parking lots, National Airport, and Bolling Air Force Base, but certainly no more difficult than getting buy-in to raise the height limit.
June 25th, 2009 at 12:00 pm
Full response. I probably won’t have time for another today.
June 25th, 2009 at 12:12 pm
He also ignores the fact that even if lots of space around a tall building is wasted, the tall building still has large savings in heating and cooling energy compared to the equivalent set of shorter buildings.
But in truly urban places like NYC there is not really much waste around tall buildings, with the exception of public housing. And in any case, most people still want to have green spaces in their cities, and that is inevitably going to decrease density. But it’s not going to increase building energy use substantially.
Also, in NYC, we have these things called basement parking garages…
June 25th, 2009 at 1:00 pm
You write:
“one could say that there are tens of square miles in the city in which heights are well below the limit, providing ample opportunity to increase density without doing a thing about the height limit. That fails to recognize that some neighborhoods, by their character, will never be upzoned.’
This isn’t strong enough. For many neighborhoods, it’s not a question of upzoning — it’s a question of demand. Many neighborhoods in dc (and elsewhere) that aren’t dense are not that dense for a reason — not a lot people want to live there. The height limit stops development and density where people want to live and where people want to have offices — downtown, dupont, what-have-you. That is, the height limit stops development for which there is demand. And the development that it stops would increase density. The fact that many buildings are short and spaced far apart in, say, parts of NE is no more relevant to the question of whether it makes sense to limit development downtown than vacant land in Reston.
June 25th, 2009 at 2:16 pm
Speaking of around the ballpark, I live right near Stadium-Armory Metro (south entrance) and I just received a flyer in the mail asking me to join a group opposed to redeveloping Reservation 13, which is essentially old DC General Hospital and, mostly, its really, really large parking lot. So, the crazy NIMBYS come out even when the proposal is to redevelop a huge, ugly parking lot right next to the entrance of an underused Metro Station. Apparently, some (hopefully a small minority)of my neighbors like having a huge sea of asphalt right next to the entrance to their Metro station. God forbid we would have new neighbors, some retail and a few decent restaurants next to our Metro station and within walking distance.
June 25th, 2009 at 5:31 pm
It’s a wonderful thing that so many promising young people have careers and blogs in Washington DC. And it’s nice to see them thinking about density.
But Washington DC is not like the other cities in America. Any problem in DC becomes a big problem because DC doesn’t really have home rule and does really have a special role to fulfill as national capital. Throw in high-powered lobbyists, columnists who can afford $2 million homes, etc etc, and you have a situation where any discussion becomes hopelessly arcane.
That said, what happens at the street level of a skyscraper is going to be what the city wants to see happen. Nobody’s paying for that land with the rents from the street-level storefronts, and usually the developer will do anything at the street level in exchange for something they want up in the sky.
Secondly, skyscrapers like to be together. For whatever reasons, you very rarely see a skyscraper developer decide that they could save a lot on land by just going three or four miles from the existing skyscrapers to build. In terms of transportation- and this nation spends a lot on transport- this density of skyscrapers can be a very good thing.
June 25th, 2009 at 5:52 pm
I believe the entire area between 9th/Sherman and 7th/Georgia in NW from M Street north to Park Rd should be upzoned. Throw in a streetcar that circulates this loop for Petworth down to the Convention center. It doesn’t have to be an upzone to 10 storys - midrise of 5-8 stories would add a lot of density.
Georgia Ave is going to have difficulty getting cleaned up and regain it’s commercial glory without this.
June 25th, 2009 at 9:11 pm
I think that you are putting too much emphasis on density.
You don’t start with density. Density is a by-product of creating interesting places. More here:
http://citycomfortsblog.typepad.com/cities/2006/02/density_is_a_by.html
June 25th, 2009 at 10:57 pm
density is a byproduct of interesting places. the problem arises when interesting places are constrained in the amount of residential and retail space they can provide because of a high limit.
I no longer live in the district, but I still can’t understand why people like the height limit. When a friend of mine came to town for inauguration, I pointed out how all the buildings downtown were 10-story boxes. Unfortunately, that was all he could see from then on. If anything, the height limit only serves to make the city more architecturally and aesthetically boring.
June 25th, 2009 at 11:11 pm
Kiril.
Yes I agree that zoning must be in place to allow greater density. No disagreement there.
But where we need to focus is on creating interesting places. Once a place has some sort of cool factor, people will compete to be there. Density will take care of itself (obviously the zoning has to allow it) if the neighborhood is one where people want to be,.
June 26th, 2009 at 9:23 am
This whole argument, amount “no more land” to build on in DC is patently false and shortsighted. We heard downtown was built out in the 80’s and early 90’s even while the old downtown was parking lots. Downtown had moved west and no one would want to be at G & 7th. Then the East End totally refilled in the 2000’s. Then DC was “built out” again. Well lo and behold, now we’ve gotten two huge new districts in NoMa and Capitol Riverfront that can accomodate millions more SF of development. In 15 years when they’re built out, undoubtably we’ll build in places that we aren’t even contemplating today, just as we’ve always done. DC’s height limit is the best thing that ever happend to this city. It, along with strong demand, has created a dense CBD not filled with parking lots and development holes and has expanded development to withered areas of the city. Go to most any other city in the country, even healthy ones, and their downtowns are potmarked by vacant land right next to 40-story towers. Our height limit has constrained supply so that development rights are valuable enough that you just don’t sit on land like in other cities. We have the third largest downtown in the nation, yet we’re the ninth largest metro. Don’t fix what ain’t broke.
June 26th, 2009 at 10:39 am
No, that is totally bassackwards. Density creates interesting places.
When increased density in high-rises reduces rents, low rents and vacant store fronts happen in less ‘dynamic’ neighborhoods. This is what Jane Jacobs was talking about- the diversity that happens where prices are low and marginal uses can survive.
But even with low prices, diverse producers need markets, whether it is a market for labor, for art, or for restaurants or services. That’s why they locate as close to density as they can, instead of moving to Wyoming or North Dakota.
What Jacobs didn’t emphasize clearly enough for the people who simply memorize her books is that this is always changing. If ‘marginal neighborhood’ is the name, change is the game. In NYC this is masked by rent control, but in any other city, if you’re getting a sweet deal on rent, you should be thinking about what you’re going to do when the rent goes up.
DC, of course, is another massively artificial economy. Talking about cities in the context of DC is like talking about neighborhoods in the context of a gated community.
But in general, density creates diversity.