Greater Greater Washington

Posts by Payton Chung

Payton Chung, LEED AP ND, CNUa, sees the promises and perils of planning every day as a resident of Southwest Washington. He first addressed a city council about smart growth in 1996, accidentally authored Chicago's inclusionary housing law, blogs at west north, and is editor-at-large for Streetsblog

Pedestrians


A 12-block "shared space" street will soon line the Southwest Waterfront

"Shared space" is the idea that some streets can work better when, instead of using curbs and traffic signals to separate users, pedestrians get priority using subtle but effective visual cues. Washington will soon have a prime example in Wharf Street SW, part of the Wharf development on the Southwest Waterfront.


Rendering of Wharf Street SW. All images from Perkins Eastman unless otherwise noted.

Streetsblog recently interviewed a key shared space messenger, Ben Hamilton-Baillie, showed off built examples in Pittsburgh and Batavia, Illinois, and discussed the potential of shared space to transform the narrow streets of New York City's Financial District.

Many of the historic examples of shared space that remain, like Market Square in Pittsburgh, Haymarket in Boston, or South Street Seaport in New York, are within what were wholesale markets or ports, where people, goods, and vehicles always intermingled. Old wharves and quays have become distinctive destinations in many cities, from Provincetown to Seattle's Pike Place Marketand an inspiration to others who want to create human-scaled environments today.

Washington, DC, had just such a working waterfront for centuries, but bulldozed almost all of it in the 1950s amidst federal fervor for slum clearance and urban renewal. Just a few weeks ago, developer Hoffman-Madison Waterfront broke ground on the Wharf, which will transform 27 acres of land into 12 city blocks housing 3.2 million square feet of retail, residences, hotels, offices, and facilities ranging from a concert hall to a yacht club. Many architects and landscape architects worked together within a master plan designed by Perkins Eastman.

I talked with Matthew Steenhoek of Hoffman Madison Waterfront about how the Wharf's public spaces have been designed to accommodate pedestrians first and vehicles (from semi trucks to the occasional police helicopter) when necessary. Below is an edited transcript.

What are the various kinds of streets and alleys that visitors will find at the Wharf?

Maine Avenue [on the land side of the site] has a pretty traditional street section with four lanes: vehicular traffic, turn lanes, parallel parking, and street trees. There will be a grade-separated, bidirectional cycle track on Maine's south side, outside of the existing street trees but separated from the sidewalk by a second row of trees. We're using permeable asphalt for the cycle track because it goes over the critical root zone for those big old street trees.

On Maine, you have a channelized design: traffic moves faster, there's a lot of through bicycle traffic connecting to the [Potomac and Anacostia riverfront] trails, so the through traffic happens there. We'll leave the median lanes utility-free and streetcar-ready, so if the District decides to build a line through there they can do so at a much lower cost.

As you move into the site, it transitions into the shared space approach. Besides the two major [entry] intersections at 9th and 7th, it's all curbless. The public street ends at the Maine Avenue cycle track, and from there in they'll be private streets. This gives us much more latitude in terms of our design approach, so we can vary from traditional street standards and requirements.


A circulation plan for phases one and two shows both shared spaces and pedestrian spaces.

Differences in paving material, texture, color, and pattern will help differentiate the spaces within the major public spaces. There's also bollards to separate the edge and center of the street in busier locations.

There are a lot of clues built into the paving, which will use a kit of different pavers. There will be a smooth and continuous path dedicated for pedestrians, while the places where vehicles are allowed as guests will have a split-block finish with a little rougher texture. In order to slow the speeds down, the paving patterns will change as you transition from one zone to anotherlike where you might be introducing pedestrians or bikes into the space. The smooth surface in no way limits where the pedestrians can go, though, and the curbless environment invites pedestrians to really use the entire space.


Most of Wharf Street's right-of-way is dedicated for pedestrians.

There aren't a lot of obstructions within the spaces. They're straightforward and kind of utilitarian, designed to be able to be closed, or partially closed, [to cars] when it's busy. Restaurant seating can spill out there, and the shared space can become a true public space.

Wharf Street runs directly along the water's edge. It has a typical section of 60 feet across, with three modules: The closest 20 feet [to the buildings] is a café seating zone, where the paving is smooth and flat so that they can move furniture around. Right outside there is a dedicated pedestrian path, then the shared movement, or travel, zoneone way for vehicles moving or parking or loading, but cyclists and pedestrians can go any which way. The movement space is the center 20 feet, using smaller, more textured pavers.

The outside 20 feet has a dual allée of trees, and it's where the fixtures and street furniture areno bollards, but there are trees. That zone, again, has a smooth texture. Along the bulkhead [seawall], there's a huge wooden timber down the side for people to sit on. We also have flexible seating all throughout. Having the flexible seating is part of the traffic calming: things are going to change and feel different every day.

Throughout the parcels, there are alleyways that come through. Those are much tighter, more intimate spaces, from 25 to 40 feet wide. The alleys are not back alleys, they're public spacesnot a place for stinky exposed dumpsters leaking things. DC got rid of most of its alley buildings [via the early 20th century's Alley Housing Clearance Commission], but the few alleys that are left are pretty great.


Alleys will welcome pedestrians, not just service vehicles.

The only place where 55 foot long trucks are allowed is at the concert hall [at the west edge of the development]. Everywhere else will only have deliveries on 30 foot trucks. Since we have retail on all sides of the buildings, it's tricky to find the "back of house" space [service entrances]. The idea has been to work with [retail] operators on loading hours, so that during prime pedestrian hours there's not loading happening, and to screen and integrate the loading areas so that they can function as good public spaces when they're not being used.

The way that the shared space is set up will encourage everyone to slow down. It's not a highly predictable zone, which gives people a false sense of securitythey don't look around themselves. The character of the space will allow it to do what it needs to do, while remaining safe and accommodating for all the different users.

Like around 7th Street Park, cars are allowed, but it's not going to be the fastest route to anywhere. There's a splash fountain and benches in the middle of the street that you have to make a one-way loop around, and another one down at the District Pier where cars will have to go around to get to Blair Alley.

There's another totally pedestrian zone at District Pier. That's the most intense area of pedestrian activity, since there's lots of things happening here [with the pier and concert hall]. We'll have another [pedestrian zone] over at M Street Landing across from Arena Stage, and a third at the Waterfront Park, which we designed through a community charrette process. At Waterfront Park, vehicular access is only to dinner cruise boats, and to the police and fire pier. Ninety-nine percent of the time that will be a nice broad path, but the open space is so a police helicopter can land right in the middle.

Can you describe the process of deciding upon a shared space approach?

That was one of the really upfront visions that [design architect] Stan Eckstut had for the site. He saw it as a true, mercantile, flexible space. Having hard curbs really does limit what you can do with the spacewhat it wants to be in 2017, and in 50 years, may be really different. Very early on, in 2008 probably, we had that 20-20-20 allocation set up for Wharf Street. It's tight enough to create a comfortable space and encourage that vitality along the water.

A lot of thought went into how to execute it, but we always knew it was going to be shared. From the start, everyone bought in on that vision of flexibility. It will be a nice change from most of the new streets and places that are being constructed around the city, some of which are very rigid and kind of sterile.


A piazza adjacent to Wharf Street will allow cars access to a hotel entrance, without providing through access.

We have a healthy storefront allowance [for retailers to design their own spaces]. Also, these blocks are relatively small by city standards, around 250 feet square. Since the citywide average is 300-500 feet, our fabric is much more porous than that. [Our historic preservation consultants] came up with a list of old alley names from the neighborhood, some of which we'll resurrect here as a link to that past. Hopefully, these approaches will mitigate the fact that everything's new. Ultimately, it needs to get lived in to feel real.

What primary benefits did the shared space approach offer?

Our reason was placemaking. For us, it was starting with a question of "what's the space going to feel like?" We wanted to bring something interesting and uniquea space that'll work tomorrow, and in 50 or 99 years, when our ground lease is done. Vehicular capacity wasn't important, since these are not continuous routes through to anywhere. Most cars will just want to go to and from the garage.

Shared space just made sense for any number of reasons. We wanted to slow the traffic down, but not with obtrusive traffic bumps. These are second-generation traffic calming ideas: adding uncertainty, variety, texture. It's saying, "Hey, you're welcome to come in as a motorist, but behave." Everyone else is going to behave. [Since they're internal streets] we could have some fun with the signage, something like "walk your car."

The exponential drop in injuries when cars only move 15 or 18 mph is very telling. At that speed, people can still communicate nonverbally, with eye contact or a nod. Get above that, and that all breaks down, and instead you have to rely on lights and signs and bumps and those crazy things. We're going a little more low key than that. If everyone's moving at or below 15 mph, you can negotiate those intersections without the need for stop lights and all that equipment.


The Maine Avenue Fish Market, a fixture of DC's waterfront that has long mixed crowds with cars, will remain at the west edge of the Wharf's site. Photo by D.B. King on Flickr.

Were there other examples that sold you on the concept?

We think that we have the right solution for this place, of course, but we did travel to see other waterfronts. Along Nyhavn, the famous slip in Copenhagen, there's two strips of smooth pavement that are the width of the pushcarts they used to unload the boats. That street section, how it feels and meets the water, was definitely an inspiration, just because it's a wonderful place. It's pedestrian only, because there's just so many people, but we have the ability to do the same.

Stavanger, Norway, did a really nice thing with the paving to differentiate parking, driving, and walking spaces. We adapted that solution here: It's all the same tone and all looks about the same, but the textures break things up without putting thermoplastic stripes and giant yellow signs. That makes for a more visually pleasing public environment, creating a public space instead of a traffic sewer.

And of course, right now on the site, the shared space that we already have today is the Fish Market. It's more of a mixing bowl, and it's functioned that way for years. It works just fine because it doesn't "work" in a conventional sense, and that's how it really works.

A version of this post originally appeared on Streetsblog USA.

Architecture


A hidden height limit holds back affordable mid-rise construction in DC

In "The Three Little Pigs," one pig builds a house from straw, a second from sticks, and a third from bricks, with very different consequences. Notably absent is any mention of each little pig's construction budget. For humans today, it's not protection from wolves, but out-of-control budgets that determine our choices of building materials.


New residential construction in Takoma. Photo by the author.

The 1899 Height Act set a construction limit of 90 feet in much of DC, effectively 7 or 8 stories. This height poses a particularly vexing cost conundrum for developers seeking to build workforce housing in DC's neighborhoods. It's just beyond one of the key cost thresholds in development, between buildings supported with light frames versus heavy frames.

Fire safety codes require that buildings over 6 stories have heavy frames, but rents in most of the city don't quite justify the considerable added cost. Instead, valuable land near downtown sits empty, outlying areas that could support taller buildings instead get low­-rise buildings, and the city gets fewer new housing units. New construction techniques could offer a way out.

The difference between heavy and light frames

Heavy frames rely on fewer but stronger steel or reinforced concrete columns to hold up the building, and are better known as Type I fireproof structures. Light frames rely on many small columns (usually known as studs), and are usually referred to as Type II (if masonry or metal) or if wood, Type III (with fire resistive treatments), Type IV (if made from heavy beams), or Type V (if little fire-proofing has been applied) construction.


Left: Type I: 1100 1st St. NE in NoMa. Right: Type III: Apartments in Fort Totten. Photos by Mr.T in DC on Flickr.

These structural types are rated using the degree of fire protection that these structures offer, with lower numbers denoting more fire-resistant structures. In DC, they're defined in the city's building code, which is based on an international standardthe International Code Council (ICC) and its "I-Codes."

The ICC's Table 503 sets limits on how high different types of buildings can be. Thanks to technological improvements to wood and fire safety improvements to buildings, mid-rise buildings can be built up to five floors high using Type III construction. These five floors can, in turn, be placed atop a one-story concrete podium to build a six-story mixed-use building.

How much cheaper?

Light frame construction cuts costs in two principal ways. Light frames use fewer materials in the first place and thus have smaller ecological footprints, particularly since cement manufacturing is one of the most carbon-intensive industries.

They are also built from standardized parts that are usually finished off-site, rather than on-site, so materials are cheaper, on-site storage and staging (e.g., cement mixers) require less space, and construction is faster. That further reduces overall construction costs, since developers pay steep interest rates on construction loans.

These cost savings really add up throughout the entire building. The ICC's Building Value Data provides a comparison of national average per-square-foot construction costs for different kinds of multi-family building construction.

$104.74Type VLow-rise wood frame
$119.77Type IIIMid-rise wood frame, fire-resistant walls
$139.01Type IIMid-rise, light-gauge steel
$150.25Type IHigh-rise fireproof

Similarly, the RS Means construction cost-estimator database provides 2012 estimates (adjusted for local prices in DC) that show an even steeper premium for high-rise construction:

$136.70Type VLow-rise wood frame, 3 stories
$162.87Type IIMid-rise, light-gauge steel & block, 6 stories
$246.32Type IHigh-rise fireproof, 15 stories

As the ICC figures show, switching from Type III to Type I construction increases the cost of every square foot by 25.4%. Thus going from, say, a six-story building to seven stories only increases the available square footage by 16.7%, but increases construction costs by 46.3%. This results in a difficult choice: go higher for more square feet but at a higher price point, or take the opportunity cost, go lower, and get a cheaper, faster building?

In most other cities, the obvious solution is to go ever higher. Once a building crosses into high-rise construction, the sky's ostensibly the limit. In theory, density can be increased until the additional space brings in enough revenue to more than offset the higher costs. As Linsey Isaacs writes in Multifamily Executive: "Let's say you have a property on an urban infill site that costs $100 per square foot of land. Wood may cost 10 percent less than its counterpart materials, but by doing a high-rise on the site, you get double the density and the land cost is cut in half."

Yet here in DC, the 90-foot height limit on residential areas, and commercial streets outside the core, tightly caps the additional building area that could pay for the substantial cost premium of building a high-rise.

Within the twilight zone

For many areas in DC, land is expensive enough to fall into a Twilight Zone. These areas are expensive enough to require high-rise densities, but the local rents are too cheap to justify high rises' high per-foot construction prices.

These areas are not super-trendy like 1st Street NE in NoMa or 14th Street NW in Logan Circle, which are seeing an explosion of Type I construction (and prices to match, with new apartment buildings selling for $900 per square foot). Nor are they outlying areas, where developers think the opportunity cost of forgoing a future high-rise is acceptable and thus proceed with Type III construction.

The recent apartment boom has given local residents a good, long look at Type III construction: in outlying city neighborhoods like Brookland, Fort Totten, Eckington, Petworth, off Bladensburg Road, and in town centers like Merrifield and White Flint.

In areas that are in-between, a lot of landowners are biding their time, waiting until the moment when land prices will justify a 90-foot high-risea situation which explains many of the vacant lots in what might seem like prime locations.

My own neighborhood of Southwest Waterfront is just one example. Within one block of the Metro station are nine vacant lots, all entitled for high-rise buildings, but their developers are waiting until the land prices jump high enough to make high-rises worthwhile amidst a neighborhood known for its relatively affordable prices.

While the developers wait, the heart of the neighborhood suffers from a lack of customers within walking distance; the resulting middling retail selection, vacant storefronts, and subpar bus service reinforces the perception that Southwest Waterfront is not worthy of investment. Nearby Nationals Park is similarly surrounded by vacant lots, with renderings of eight-story Type I buildings blowing in the breeze.

In NoMa (east of the tracks) and the western end of H Street NE, projects like 360 H and AVA H Street were redesigned after 2008's market crash so that they didn't require Type I construction. The redesigns reduced costs, reduced the developers' need for scarce financing, and made the projects possiblebut also reduced the number of units built. AVA was entitled for almost 170 units, but was built as 138 units: building 20% fewer units cut structural costs by over 40%, according to developer AvalonBay.

Elsewhere, some other development projects have similarly been redesigned with faster Type III construction, even as future phases assume Type I construction. Capitol Quarter, the redevelopment of Capper/Carrollsburg near Navy Yard, might win an award for the shortest time between announcement and groundbreaking for the mixed-income Lofts at Capitol Quarter.

Several blocks west, the first phase to deliver at the Wharf will be the last phase that was designed; in fact, the idea of redeveloping St. Augustine's Church as a new church with a Type III residential building above came years after design began on the high-rises to its west.

New technologies can break the logjam

If it weren't for the Height Act, developers wouldn't just sit and wait on sites like these. They'd probably just build Type III buildings, and if there's still demand, they could build Type I downtown towers with 20+ floors. But due to the Height Act, DC is one of the only cities in America where there's a substantial market for 7-8 story buildings.

To break this logjam without changing the Height Act, DC's building community can embrace new light-frame construction techniques that can cost-effectively build mid-rise buildings without the need for steel beams and reinforced concrete. Local architects, developers, and public officials could convene a working group to bring some of these innovations to market, and thus safely deliver more housing at less cost.

Cross laminated timber (CLT), a "mega-plywood" made of lumber boards laminated together, has sufficient strength and fire resistance for high-rise structures; it's been used to build a 95-foot residential building in London and a 105.5-foot building in Melbourne. The ICC has approved CLT for inclusion in its 2015 code update, but the city has leeway to approve such structures today under a provision that allows "alternate materials and methods."

Cities like Seattle have started to evaluate whether to specifically permit taller CLT buildings. The Bullitt Center, a zero-impact building in Seattle, uses CLT for most of its upper-story structure.


The Bullitt Center. Photo by the author.

Type II buildings, often built with light frames of cold formed (aka light gauge) steel, can achieve high-rise heights but the ICC limits them to the same heights as Type III. (For example, 360 H Street was re-engineered from Type I to Type II, and lost two stories in the process.) Prefabrication, hybrid systems that incorporate other materials, and new fasteners have made mid-rise Type II buildings stronger and most cost-effective.

However, as the RS Means chart above shows, Type II might be cheaper than Type I but remains more expensive than Type I. Similar prefabrication has been applied to Type I mid-rises on the West Coast to reduce their costs.

By embracing these advancements in structural engineering, as well as providing relief from onerous parking requirements, DC could more easily and affordably build the mid-rise buildings that will house much of the city in the future.

Thanks to Brian O'Looney, partner at Torti Gallas and Partners, for sharing his expertise. A version of this post appeared on West North.

Development


As it turns out, suburban sprawl actually peaked 20 years ago

The rate of suburban sprawl peaked in the mid-1990s and has declined by two-thirds since then, even through the giant housing boom. Could this quiet change in land use have caused many of the changes that we're seeing today, from recentralizing job growth to the decline in driving?

Sprawl is slowing
Graph from the USDA.

According to the USDA's 2010 National Resources Inventory, which tracks land use with satellite imaging surveys, the inflection point for suburban sprawl peaked in the mid-1990s, just as "smart growth" emerged onto the national scene. That's before the giant housing bubble showered suburbs with seemingly limitless sums of capital.

It's been slowing ever since then, even though metro population growth moderated only slightly (see graphs on page 3). Interestingly, non-metro population growth (including distant exurbs beyond metro area boundaries) in the 2000s fell much faster than metro population growth.

It's interesting that the slowdown in sprawl, like the slowdown in mall construction, predated "peak car" by 10-15 years. The directionality might be backwards: the 1980s cessation of massive freeway construction may have pushed many metro areas into some version of Marchetti's Wall: the theory that people don't want to travel more than one hour a day, and thus that metropolitan growth has geometric limits tied to how far the predominant mode of travel goes.

Edge Cities, which relocated commercial uses into the inner suburbs, could only extend the outward trend so far; with a few notable examples, attempts at building Edge Cities in outer-ring suburbs has largely failed, since there's no meaningful centrality amidst the undifferentiated masses of one-acre lots. Second-generation Edge Cities rarely thrived, because without new beltways there just wasn't the population base to feed them.

To this day, 80% of the office market in metropolitan DC is within three miles of the Beltway, using Cassidy Turley's submarket definitions. Joel Garreau wrote that in the late 1980s, Til Hazel "had major projects at half the exits on Interstate 66 from the Beltway to...Manassas," but ultimately, that future didn't pan out.

Reston and Herndon, located 10 miles from the Beltway and 20 miles from the White House, are the notable exceptions that proves the rule. Fair Oaks and Gaithersburg, located 17 and 19 miles from downtown DC respectively, are doing just fine. But almost 35 years after their shopping malls opened, they're still ultimately peripheral locations relative to the metro area.

Even in metro Boston, which uniquely among Northeast metros actually built an outer beltway, 73% of the office market is within the urban core or inner ring, and the urban core commands per-foot prices more than twice as high.

If you consider that the area of a circle grows with the square of its radius, a slowdown in the areas developed for sprawl would imply a much steeper decrease in the radius of metro expansion. This could imply another overlooked factor in the slowdown in VMT growth, or vehicle miles traveled: since metro areas are no longer getting geometrically wider, thus distances between metro-area destinations are no longer growing as fast.

A majority of the VMT benefits from more-central locations come from the fact that destinations are closer and car trips are shorter; only a minority of the benefits come from a switch to other modes. As growth recentralizes, perhaps VMT can be expected to decline further.

A version of this post appeared on West North.

Architecture


No, DC is not going to be like Paris

Supporters of DC's height limit say restricting building heights has worked to keep Paris beautiful. But embracing the Parisian built form would have unintended consequences on DC's neighborhoods.


Demolition near l'Opéra in Paris, 1877. Photo by Charles Marville

The mid-rise Paris that we know today was built not by a democracy, but by a mad emperor and his bulldozer-wielding prefect. As Office of Planning director Harriet Tregoning said in a recent WAMU interview, "Paris took their residential neighborhoods and made them essentially block after block of small apartment buildings."

"If we were to do that in our neighborhoods, we could accommodate easily 100 years' worth of residential growth," she added. "But they would be very different neighborhoods."

A haunting exhibition of photographs by Charles Marville, now on view at the National Gallery of Art, offers us a glimpse at how this change manifested itself in Paris.

The city government hired Marville to document the systematic demolition of central Paris' low-rise neighborhoods, the construction of new mid-rise neighborhoods (the ones we know today) in their stead, and the widespread displacement of the center's low-income residents to the urban fringe. (Numerous books have been written about the era, notably "Transforming Paris," by David Jordan.) There were technological limits on buildings in that era, too: elevators were slow and expensive, and the new water mains could not supply satisfactory water pressure to the upper floors of many buildings.

Not dissimilarly, downtown DC's horizontal march has steamrolled numerous low-rise neighborhoods in its wake, from Chinatown to Foggy Bottom. Now that only a few blocks are left for downtown to grow into, office buildings are muscling into Shaw. This is only natural for a mid-rise city: Paris' mid-rise urban fabric superimposed on DC would spill outside the diamond, vastly larger than the existing downtown.

That path of destruction is why most other growing cities in this century (i.e., built-out but growing central cities, from London and Singapore to New York, Portland, Toronto, and San Francisco) have gone the Vancouver route and rezoned central industrial land for high-rises. This method allows them to simultaneously accommodate new housing, and new jobs, while keeping voters' single family houses intact.

By opposing higher buildings downtown, DC's neighborhoods are opposing change now, but at the cost of demanding far more wrenching changes ahead: substantial redevelopment of low-rise neighborhoods, skyrocketing property prices (as in Paris), or increasing irrelevance within the regional economy as jobs, housing, and economic activity get pushed further into suburbs that welcome growth.

Among large North American cities, only Toronto has joined DC in making a concerted effort to redirect growth into mid-rise buildings along streetcar lines, and only as an adjunct strategy in addition to hundreds of high-rises under construction. (The two metro regions are of surprisingly similar population today.) Yet there, just like here, neighborhoods are up in arms at the very notion.

DC cannot put a lid on development downtown, in the rowhouse neighborhoods, in the single-family neighborhoods, and on the few infill sites we have left, and yet somehow also accommodate enough new jobs and residents to make our city reliably solvent, much less sustainable. The sum of remaining developable land in the city amounts to 4.9% of the city, which as OP demonstrates through its analysis, cannot accommodate projected growth under existing mandates.

Something will have to give. A good place to start is a loophole-ridden law imposed back when DC was a protectorate and when Greater Washington counted fewer residents than today's Asheville or Quad Cities.

The Office of Planning has suggested a reasonable framework for a subtly revised Height Act that can accommodate growth and change while preserving the city's cherished urban design and historic neighborhoods. Adapting the rigid 130' cap to a street-width rule maintains the Height Act framework along our ceremonial avenues, where our city's namesake actually set a height minimum.

Along streets like L'Enfant Promenade, Washington had the right idea: taller buildings will better frame vistas. Beyond the L'Enfant City, the Comprehensive Plan and zoning ordinance will continue to ensure that most buildings never reach the 90' Height Act maximum, but the city will have the flexibility to adapt to evolving construction techniques and special opportunity sites.

As DC re-adjusts to a new century of urban growth, after a lost generation of population decline and disinvestment, inaction poses a far greater risk than action. Paris' combination of horizontality and verticality is undeniably beautiful, but its unique form resulted from a peculiar historical process that I would not wish upon an American city today.

The District of Columbia Council is accepting written testimony about the Height Act until next Tuesday. For more information or to send your comments, visit their website.

A version of this post appeared on West North.

Architecture


Reflective surfaces can brighten Metro stations

Many complain that Metro's subway stations aren't bright enough, but they're surprisingly not that dim compared to other systems. Better surfaces can ensure that the limited lighting available is used more effectively without altering Metro stations' iconic appearance.

Which of these stations do you think is better lit? This one in Vancouver:


TransLink system lighting standard for subway platforms: 4 foot-candles. Photo by monnibo on Flickr.

Or WMATA's Gallery Place-Chinatown station?


WMATA system lighting standard for subway platforms: 10 foot-candles. Photo by thisisbossi on Flickr.

Believe it or not, Vancouver's transit agency specifies platform lighting 60% dimmer than WMATA's: their standard is 4 foot-candles, versus 10 foot-candles for WMATA. I usually read when I'm aboard transit, and whereas I have to seek out light on Metro subway platforms, I've never thought twice about the brightness on TransLink platforms. (Admittedly, I've spent much less time on the latter, partly due to the automated system's startlingly low headways).

It's not how much lighting, but how to use lighting

The difference is that TransLink also specifies high-reflectance, light-colored walls and floors, which direct light into occupied areas so that they feel much brighter. With "passive illumination," it's not just how much light is used, but also what the space does with that light.

Seemingly minor increases in reflectance for surfaces like walls and ceilings, particularly for indirect lighting scenarios, proportionately increase the brightness one can achieve with a given amount of light.

By comparison, much about the classic Metro station design thwarts attempts at improving lighting, and in fact intentionally so. Our standards of brightness have increased, partly because illumination has become so cheap.

Yet the stations' dark material palette, which includes unpainted concrete walls and ceilings, burgundy tiles, chocolate brown panels, even the bronze railings, absorbs what little light new fixtures add. These materials also attract dirt, which further darkens the stations over time.

Metro points to the efforts that it's taken recently, including regular power cleaning of the concrete station vaults, existing efforts to add fixtures, and replacing lighting fixtures system-wide with more modern (and thus brighter and more energy-efficient) equipment. The fruits of these can be seen at stations like Judiciary Square, which does indeed seem like a beacon of light compared to others in the system.

Reflective materials can improve lighting

However, using more reflective materials can also improve station lighting. That's the gist behind Metro's proposed changes to the Bethesda station, like replacing brown metal panels and concrete walls with brushed metal and clear glass. These changes will definitely help, but a more comprehensive approach could look at other changes that can improve lighting without dramatically impacting the stations' canonical appearance.

Laying a clear polymer coat on existing concrete surfaces could increase reflectance, reduce porosity and repel dirt, making cleaning easier. Painting the station vaults has proven controversial throughout Metro's history: Zachary Schrag's book The Great Society Subway points to a 1968 disagreement between the designers Harry Weese and William Lam as to whether to paint the vaults, and notes Weese's "commitment to 'pure structure in plain concrete' " in criticizing a 1990s decision by WMATA to paint some vaults.

But advances in construction materials now mean that light reflectance surprisingly has less to do with color as one might expect. A darker color with a slight gloss reflects more than a brighter color with a dull finish.

Today, much of the lighting in underground stations come from fluorescent tubes recessed within wells that are out of sight, beyond the platform edge or between the tracks. Since these surfaces are so close to the light sources, small changes here will result in big changes throughout.

Cleaning and brightening surfaces within these wells will result in more light reflected upwards into the station, as well as adding reflectors below the tubes to "catch" light that's currently pointing downwards, moving wire conduits so that they're below lights instead of blocking them, and replacing bronze-colored diffusers above the between-track tubes with clear plastic diffusers.

The stations' coffered ceilings have acoustic panels in them, which can be made brighter. These panels cover a surprising amount of the vaults' surface area, but because they're literally in the concrete's shadows, we don't tend to notice them very much.

These, too, accumulate dirt and dust over time, and over time they could be replaced by more reflective panels. The new Rosslyn entrance has highly reflective panels embedded within its coffers, which I didn't even notice the first few times I walked through it.

Similarly, WMATA could replace the drop-ceiling tiles underneath station mezzanines with tiles that reflect more light. Given the low ceiling heights in these spaces and the fact that they're largely hidden from view, a more ambitious upgrade could replace these with ceiling tiles with embedded LED lamps, reducing both shadows and glare in these areas while improving efficiency over the existing can lights. LED ceiling tiles might sound gaudy, but look no different than the fluorescent panels embedded in most office drop ceilings.

Attention to these details can ensure that the maximum possible amount of light is available within Metro's subway stations, improving energy efficiency, safety, comfort, and accessibility without altering their iconic appearance.

History


An alien notion: 800,000 DC residents

Over 800,000 people lived within the boundaries of the District of Columbia back in 1950. How did all of these people fit, with fewer and smaller buildings than today?


Photo by Jesse Means on Flickr.

The 1951 sci-fi classic "The Day the Earth Stood Still" inadvertently shows us how. Klaatu, a level-headed extra-terrestrial emissary, escapes captivity at Walter Reed Army Medical Center. He wanders down Georgia Avenue, away from not-yet-nuclear-weapon-free Takoma Park, and attempts to disappear into everyday DC.

To do so, Klaatu checks into a boarding house at 14th and Harvard in Columbia Heights. Each room houses one or two people, and as such there's scant privacy to be had: everyone overhears everything.

This is convenient for Klaatu, who knows little of Earthlings' simple ways, but probably annoying for the Earthlings. Conditions like these were common in DC homes at the time.

The 1950 census found 14.1% of the District's 224,142 occupied housing units to be "overcrowded" (with over 1 person per room). By 2011, that figure had fallen by 2/3, to 4.7%, similar to the 5.3% of homes in 1950 that were extremely overcrowded (more than 1.5 occupants per room).

This crowding meant that on average, every apartment and house in DC had one more person living inside: households were 50.2% larger! In 1950, 3.2 people occupied each dwelling unit. In 2007-2011, the number of persons per household had fallen to 2.13, so the city's population still fell to 617,996. That decline would have been much steeper had the city not built 74,760 new housing units: the city's population would have plunged to 477,422, and the nation's capital would be less populous than Fresno.

Household size shrank nationwide as families changed. In 1960, married couples with children outnumbered single-person households almost three to one. In 2010, singles easily outnumbered nuclear families nationwide, and by 5.57 to one in DC.

As DC. gets reacquainted with the notion of population growth and begins to plan for a much larger population within the same boundaries, we'll have to have a realistic conversation about household sizes and housing production. A change of just 0.09 persons per household means the difference between planning for 103,860 or 140,515 additional housing units,1 or a total of 35% to 47% more units.

That amounts to 2,000-3,000 additional units per square mile of land, after subtracting the 10.5 square miles of parks and 7 square miles of water from DC's 68 square miles.

Klaatu, unfamiliar with our contentious Earth politics and "impatient with stupidity," might propose to build a platform of 5-unit-per-acre suburbia above the existing city, or require every second or third home to be subdivided, or return to 1950s household sizes and require every home to take in one boarder (not necessarily extra-terrestrials). But since Klaatu is no longer with us, we will instead have to figure out more complicated ways of infilling a built-up city.

We've obviously figured it out before; after all, DC has added an Alexandria's worth of housing units to its existing housing stock since 1950, plus plenty of offices, museums, hospitals, parking garages, and the like.


1615 M. Image from Google Maps.
A lot of that change has happened around places like 1615 M Street NW, the address where a 1954 radio version of "The Day the Earth Stood Still" placed Klaatu's boarding house. Today, 1615 M is a 9-story Class A office building that brackets the historic Magruder and Sumner schools.

The area above K but below Massachusetts was a high-density mixed residential area in the 1950s, what Park & Burgess would've known as "the zone in transition," but today the height-constrained central business district has spread north to Massachusetts Avenue. Yet in fact many foreign visitors still board on that block, at the Jefferson Hotel and the University of California's Washington Center.

Unlike in the movie, there is no way that Klaatu can make DC's growth "Stand Still," and so the built fabric of many other DC neighborhoods will have to change in the near future. Thankfully, neither is there a grumpy Gort (pictured above) parked on the Ellipse, who will destroy the earth with laser-beam eyes if we don't all just get along.

A version of this article was previously posted at west north.

1 Based on this 2006 Urban Institute/Fannie Mae Foundation report by Margery Austin Turner forecasting 100,000 new residents, a target that the Sustainable DC Plan recently raised to 250,000.
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