Hill Heat is “focused entirely on covering global warming developments on Capitol Hill.” A recent post points to the Alex Steffen article My Other Car is a Bright Green City and provides links to the many blogs that commented on that piece.
Steffen makes the point that a modest increase in housing density goes a long way to reducing use of cars by making walking possible where it otherwise might not be.
And the amount of density the study’s authors call for is extremely modest. They encourage building new projects at a density of 13 homes per acre, raising the average national density from 7.6 units per acre to 9 an acre.
To give you a sense of how gentle a goal that is, consider this: the turn-of-the-century Garden City suburbs, with their generous lawns, winding streets and tree-lined boulevards averaged 12 units an acre. New Urbanist suburbs, not particularly dense, weigh in at 15-30 units per acre. Traditional town house blocks have as many as 36 homes per acre. Parts of Manhattan, I’ve read, can reach 160 units per acre, but even without crowding together high-rises, many extremely livable parts of Vancouver have 40 homes per acre.
I admit to having a hard time visualizing what 13 or 30 homes per acre might look like. The basic facts don’t help much either:
- 1 acre = 4840 square yards (about 70×70 yards or 209×209 feet)
- 1 square mile = 640 acres
But this was useful:
Using an American football field as basis, an acre is 91 yards long and the full width of the field. Here’s what an area with a density of 6 homes per acre looks like:
Built 50 to 60 years ago, the houses themselves are about 1,200 sq ft (800 ground floor, 400 upstairs) — small by current standards. The lots are about 50×120 ft. The homes in the photo were probably first populated by GI’s and their families just after World War II.
Housing density is more formally measured in dwelling units per acre (du/ac), because at 12, 25, and 50+ du/ac we’re not talking just about houses but a mix of things like rowhouses, townhouses, condos, and highrise apartment buildings.
For an idealized view of what sort of structures go with various housing densities see here. That source (“developed to help members of the public better understand the circumstances, issues and potential solutions to the problem of housing affordability and growth in Los Angeles”) says, “The typical single family neighborhood in Los Angeles is about 5-8 houses per acre.” But most people in the region don’t live in typical single family neighborhoods, and, with the area expected to grow by 5.3 million (30%) over the next few decades, proportionally fewer will.
[For a slightly less idealized view of high density living — from 7 to 110 du/ac — see this 14 MB PDF from the Metropolitan Design Center of the University of Minnesota with photos and data from the Minneapolis and St. Paul area.]
Alex Steffen has a good idea. Let’s build more walkable living/working/shopping areas. But let’s not kid ourselves. Many of our metro regions are so incredibly overpopulated only a reduction in the number of people can make them sustainable, healthy places to live. Many of them are in a constant struggle just to provide water to their residents and businesses (LA, Denver, Phoenix, Atlanta), yet they continue to grow.
It is times like this I wish you guys would bite the bullet and go metric.
You and me both, Terje. The US started to in the lates seventies, but then Reagan got elected and thought it was anti-American. Well, that’s my short version.
For the above, I guess all you need is
1 acre = 4,047 sq m ~= 0.4 hectares
10 du/ac ~= 25 du/hectare
I love this blog.
However, I have to slightly disagree with this post.
I live in South Philly right now. There is no shortage of cars. When people have no room to park, they park in the crosswalk, they park on the sidewalk, some cars are even parked at the space on the corner of the street in between two cross walks. If they could easily stack cars here, they would.
I have lived in denser neighborhoods, and less dense, and I have biked everywhere.
I didn’t bike because my neighborhood was dense, but because I wanted to.
Of the places, I have biked, the ones that are the densest have been the _least_ pleasant to bike because there is no room for cars to pass us. Set aside the fact that any passing car will get stuck in traffic immediately.
Conversely when riding in the less dense areas where they actually have trees, cars have been very nice to us.
I believe that the difference is the people’s minds. People have decided to act a certain way. Like minded people attract like minded people.
We are going to leave this place behind and never come back. We are definitely going to move to a less dense place. We’ll continue to bike.
Continue the good work.
Thanks for that, Leroy. Higher density housing has to go hand-in-hand with more public transit as well as bikes (and provisions for biking) and walking. It will take a long time for America to change.