Greening the DC Zoning Code?

The newly released draft of Washington DC's zoning code, as reported by Greater Greater Washington, contains promising changes, including reduced parking requirements and the allowance, after a decades-long ban, of homes on alleys.  Also new to the code is the proposed "Green Area Ratio," a regulation that is molded on similar laws found in European cities such as Berlin and Malmo.  A version of the same idea, the so-called "Green Factor," has already been implemented in Seattle, where it has drawn praise and some criticism. 

The basic idea of the GAR is this: in order to address a perceived imbalance of paved/built to green space in urban areas, the zoning code must mandate dedicating a certain proportion of each lot to landscaping or permeable surfaces.

 According to its proponents, the GAR will push buildings to better treat stormwater, improve air quality and reduce urban "heat islands." However, the draft regulations do not appear to contain any standards to determine whether landscaping elements actually aid in stormwater retention or treatment. Nor is there information about whether the estimated benefits are large enough to matter regionally or city-wide.

Existing research also raises potential concerns that nobody will monitor the environmental performance of these features once built. George Washington University professor Melissa Keeley, whose work the draft documents cite, sounds a cautionary note about "policy deficits and the lack of adequate outcome monitoring" in her 2011 study of Berlin's green ratio.

Some of the benefits seem questionable, like the statistic that "1,000 square feet of green roof can supply 110 people with oxygen." While this is beneficial, that the carbon monoxide-emitting motor vehicle creates much more pollution in urban areas than the lack of landscaped surface.

Berlin's air quality, which some sources estimate is the cleanest in Europe, largely owes its success to car restriction zones and policies that encourage traveling by foot, bicycle and mass transit. Cities are unlikely to substantially improve air quality without confronting the role of the car.

Additionally, GAR does not appear to distinguish between non-green ground coverage. An asphalt-covered surface parking and a 10-story apartment building with no parking and which covers its entire lot both receive a GAR of zero. On the other hand, it appears that the same apartment building with a 160-car garage but with a green roof could earn a high GAR.

The most notable element of the GAR is, perhaps, what it does not include. Single-family homes receive a special exemption from the proposed regulations because, the hearing report states:

Implementing this standard would impose an undue financial and logistical burden upon homeowners. Properties with one-family dwellings typically maintain higher standards of landscaping and retain more green area.

Imposing expensive mandates on multifamily housing while exempting single-family homes from regulation creates a perverse outcome in which dense, space-efficient housing suffers penalties for being environmentally unfriendly, while low-density homes occupying a small portion of their lot enjoy rewards for "retaining more green area." While the GAR is compatible with high density urbanism, regulations which apply differently to various densities can make some types of housing more expensive, especially small apartment buildings.

The proponents of the New Urbanism, meanwhile, have been working to address stormwater management from an unapologetically pro-urban perspective, recently engaging the EPA in a discussion over existing stormwater standards that may inadvertently penalize density and enourage sprawling development.   Laurence Aurbach's article Dense and Beautiful Stormwater Management discusses these issues in depth, suggesting that planners and regulators accept density as a best management practice for stormwater.

Ultimately, certain landscape elements, green roofs and other innovations may have an important role to play in Washington, but residents deserve to learn more about the long-term costs and benefits of such a large scale, mandatory and relatively untested regulation before adopting it as part of the zoning overhaul.


In old cities, the highest art is often maximizing visible greenery while minimizing GAR. That creates streetscapes of intense greenery at low cost. The tools of this approach are not swales and rain gardens, as useful as these may be, but window boxes, hanging pots, climbing vines and clay urns:

Flickr/Ela2007

Eguisheim, Alsace

Taipei, Taiwan.

Flickr/Joanna_Young

Cagliari, Sardinia.

Exploring "The Greatest Grid"

The new exhibit "The Greatest Grid" at the Museum of the City of New York is well worth a visit for anyone with even a passing interest in urban planning or the history of the city.  An accompanying exhibit of speculative urban designs, however, provides evidence that the heroic materialist ideal has been slow to loosen its grasp over the minds of some practitioners in the fields of architecture and urban planning.

Simeon DeWitt's 1794 plan for Albany:
large blocks and wide streets.

Before featuring a few of these, though, a few words on the main exhibit.  Despite curator Hillary Ballon's evident admiration of New York's grid plan, the exhibit is evenhanded in its presentation, quoting liberally from critics such as Clement Clarke Moore (who famously quipped that the commissioners were "men who would have cut down the seven hills of Rome.")*  Not only the early 19th century era, but the entire subsequent century of growth and change is covered.  The featured historic maps and photos of the city are beautiful and fascinating.

There are also copies of the plans of other cities of the era, including L'Enfant's plan for Washington D.C. and (later commissioner) Simeon DeWitt's 1794 plan for a northern extension of Albany, which shows the same grid of oversized blocks and uniformly wide streets that would reappear a thousand times in the settlements of the following century.  The web of narrow streets and small blocks by the waterfront, a legacy of Dutch administration, was, as in New York, not eradicated, but evidently was not seen as an object of any interest, except as an example of a characteristics to be avoided.

Of particular interest to me were the photos of the shantytown settlements that occupied large parts of Manhattan through the end of the 19th century.  One interesting fact from the exhibit: Jacob Riis, the famous social reformer, opposed the eviction of shantytown inhabitants and the demolition of their dwellings, arguing that the self-built homes of the squatters provided accommodations superior to, and more affordable than, the tenements of the Lower East Side.

The partner exhibit, "The Unfinished Grid: Design Speculations for Manhattan", is interesting for somewhat different reasons: not so much for introducing viable design proposals for the city, but for shedding light on the imaginations of contemporarary architects and planners.  The proposals on display seem to draw from three basic sources of inspiration:

• Heroic Materialism. This term, which I'm borrowing from Nathan Lewis (who in turn borrowed it from Kenneth Clark), describes an aesthetic preference for monumental scale and the image, as much as the reality, of technology and engineering prowess.  Nathan dates it to approximately 1780, although it has Baroque antecedents and yet truly came into its own only around 1900, when Western imaginations were already trending toward urban gigantism. It grew in influence in the 1920s and 1930s, with the ideas of Corbusier and other Modernists, and remained the dominant force in theoretical urban thinking at least through the 1960s (the suburban reality on the ground notwithstanding).
• "Green" Urbanism.  Although this line of thinking was anticipated by the Broadacre City of Frank Lloyd Wright and the garden city movement, the current incarnation emphasizes an integration of natural forms, and especially agriculture, into urban areas, as well as sustainable building practices, without necessarily disparaging density.  Still, there is a degree of overlap with heroic materialism: "green" practices often rely on high-tech, rather than traditional technologies, while the tower-in-the-park form advocated by the Modernists, heroic materialist in scale, also reflects garden city influences.  Green projects can also be incremental, as below, but share a distinct focus that differentiates them.
• Incremental Urbanism. Only two of the eight featured projects reflected this approach, which seeks to make more modest and gradual changes to the urban fabric, observing the city as it stands, reinforcing those qualities already found to be beneficial while addressing perceived shortcomings.  It is by far the most "Jacobsian" of the three, but also the least flashy, and least likely to lend itself to dramatic illustrations or other flights of visual fancy.

On to the exhibits:

Heroic Materialism: At left, giant skyscrapers dwarf the Empire State Building in a plan that called for zoning limits to be rescinded for all lots facing on north-south avenues (and presumed that developers would respond with towers obviously inspired by the Emerald City). At right is an architect's idea of some vast megastructure looming over the northern end of Central Park, with father and young son enjoying the park underneath projecting towers.

What about building 40-story towers on landfill sunk into the 50-foot deep waters of the Hudson river?  Cruise ships thread channels between buildings.

From a Green Urbanism perspective, why not tear up 71st street and replant it with wheat?  At least the streets would be car-free under this proposal, and the view is human-scaled and at street level.  More fundamentally, this proposal does recognize that the vast amount of Manhattan given over to wide surface streets represents a greatly under-exploited urban resource.

Tesselated housing in the sky -- they can't be serious, right?

Finally, 6 1/4 Avenue, by Ksestudio, which proposes opening a new 40-foot wide street between and parallel to 6th and 7th Avenues that, according to the designers, "activates the depth of the base of the New York tower by multiplying the public perimeter of the block."  Simple and elegant, simultaneously addressing the excessive width of the midtown blocks and the lack of additional north-south routes while greatly adding to the amount of accessible street frontage.  Feasible?  Maybe, maybe not, but the method is thoughtfully incremental.  No flashy graphics were included, just clear and concise figure-ground drawings.

That's all I have for 2011. See you in the new year!

*Stephen Smith has recently covered some other critiques of the plan here.

Litigating LEED

Although LEED building standards have come under criticism in recent months for the excessive costs they impose on new construction, a lawsuit currently proceeding in the Southern District of New York alleges that there is no evidence that LEED-certified buildings even deliver their promised energy savings.  The most recent complaint, available here (courtesy of the Green Real Estate Law Journal which has much more on the story), brings counts in false advertising and deceptive trade practices against the U.S. Green Building Council (USGBC) for promoting LEED standards as energy-efficient when, according to the complaint, the sole study on the subject indicates, on average, higher energy usage for LEED-certified buildings.

One of the major points of contention is that the USGBC in the past awarded LEED status for design features only, while failing to track and report whether these features actually led to subsequent reductions in energy usage — which a cynical observer might interpret as a focus on the image, rather than the reality, of energy efficiency and environmental stewardship.  (The USGBC has since instituted a reporting requirement, although certification will continue to be awarded at the time of project completion.)

The merits of this particular suit aside, the LEED standards have been faulted for other reasons (by no means an exhaustive list):

• By historical preservationist groups claiming that the standards encourage tear-downs rather than rehabilitation (in an odd echo of mid-20th century urban renewal incentives);
• By planners who point out that the standards' failure to take into account location (now addressed somewhat by a revised ratings system) resulted in LEED platinum certification going to projects on exurban greenfield sites accessible only to cars;
• For not tackling the issue of minimum parking requirements given that driving habits contribute far more to total energy use than in-home heating, cooling and lighting systems;
• For inexplicably providing bonuses for reducing building footprints thereby encouraging sprawling patterns of development.

To its credit, the USGBC seems to be well aware of these criticisms and is committed to revising the standards on a regular basis with public comment sought.  The cascade of unintended (albeit, in many cases, quite forseeable) consequences, though, will present a challenge for any future LEED drafters.