High rises’ high costs, part 2: Land-efficient, but not floorspace-efficient

clearing

High-rises, like these in Calgary, may be land-efficient, but aren’t really floorspace-efficient.

I wrote earlier about how higher per-square-foot construction costs make high-rise housing considerably more expensive to build than low-rise housing. Those higher prices don’t stem from any one factor; costs for everything increase as buildings get taller (courtesy James Barton and Steve Watts of Davis Langdon/AECOM, in a CTBUH Technical Paper):

Elements of higher cost for high-rises

Increasing building heights doesn’t linearly decrease the cost of land per unit, as economic theory suggests, since taller buildings cost more (and in non-linear ways): they cost more to build, and they inherently waste more of their floor space.

The “efficiency” of high-rise (and mid-rise) buildings is typically lower than for low-rise buildings, and as Tom Steidl points out, especially so under American building codes. “Efficiency” in this context is an architectural term describing the “net to gross” ratio, of “rentable” or net internal area to gross internal area. As Steve Watts of Davis Langdon/AECOM points out in CTBUH Journal:

Tall buildings are less efficient than low-rise schemes because:
– Structural frames and core walls are larger and thicker
– More area is taken by plant and risers
– Smaller floor plates result in relatively high space-taken by lifts, stairs, circulation, etc.

Floorplate efficiencies of high-rises at various heights

Essentially, connecting all of the stuff above down to the ground requires taking space away from all the floors below. Every additional floor requires a tiny slice of every single floor below. The result is that 15%-25% of a high-rise’s floor area is typically wasted space. Steidl helpfully shaded these diagrams of towers in Vancouver (88.8% efficient) and Los Angeles (80.9% efficient), with net square feet in orange:

Ground-related housing types minimize this efficiency loss by eliminating interior hallways and vertical circulation. A typical Chicago three-flat achieves almost 90% net-to-gross efficiency. Alternate designs, like Montreal’s exterior-stair triplexes or the “Charleston triplex” (a Torti Gallas invention at King Farm that gives three flats their own internal staircases) can yield even higher efficiencies, approaching 100% — while achieving densities exceeding 30 dwelling units per acre.

Putting the two together, a high-rise unit faces a 15% efficiency penalty, and a 40% (or higher) cost penalty per square foot. The compound penalty of these two factors amounts to a 60% (or higher) construction cost premium per high-rise unit.

What’s more, interior common areas don’t just have to be built today; they have to be maintained tomorrow — a subject for another post.

On definitions: equitable communities, magpie infrastructure, vibrant centers, gentrification

Bellevue goes upscale

Bellevue was not one of the “suburban vibrant centers” examined for a NAIOP report on office occupancy trends.

Some recent reports left me appreciative of their aims and ends, but not exactly how they got there, and in particular with how other analyses have defined key terms.

1. The Living Community Challenge certainly provides an inspiring goal to reach for, notably in its use of elegant performance criteria that broadly require “net positive” environmental performance on site — broadly, that new developments can strive to shrink their ecological footprints to fit within their actual footprints. It also pretty seamlessly integrates the Transect throughout, and in a balanced way that sometimes rewards and sometimes penalizes both ends of the spectrum.

However, having participated in the creation of LEED for Neighborhood Developments, it’s telling that some of the same battles in that scheme have emerged within this one. Prescriptive approaches still occur throughout, and some of the personal-health ones are somewhat wishy-washy. (The emerging science of health impact assessments may have been a useful complement here.) The equity section (“petal”) has a lovely intro, but its imperatives don’t address many social criteria — affordable housing is a notable omission — and almost entirely use prescriptive standards. Another long-running debate was over the use of prerequisites in the rating scheme: It seems strange that a baseline, “Petal Community” certification can be done while ignoring a majority (four of the seven) of the petals.

I’ll be interested to learn more about the Challenge in the coming weeks, and to see how others feel about whether it’s rigorous and balanced.

2. Kriston Capps brings up Mikael Colville-Andersen’s term “magpie infrastructure” in a recent CityLab piece. Bicycle and pedestrian infrastructure, examples like the Bloomingdale Trail aside, rarely needs architects’ attention — their structure-first solutions are usually fundamentally anathema to bicyclists’ lazy inclination to not climb hills. By and large, people should be encouraged to stay at grade, and landscape architects and engineers should be entrusted with their care.

Closer to MCA’s home, the current BIG exhibit at the NBM includes Loop City (video; skip to 2:30), a proposal for an elevated rail loop around Copenhagen + Malmo. The proposal lifts up the stations so that trains decelerate on the approach and accelerate as they exit — a clever idea lifted from subways like Montreal’s. When done below-ground, this brings trains closer to the surface just where they’re needed, but when above-ground, the same approach antagonizes the energy needs of the passengers (who need to climb ever-higher escalators to get to the platforms) and the energy needs of the trains.

Another obvious flaw is that the proposal repeats the Corbu-in-Algiers mistake of thinking people would want to live in flats beneath a railway, without realizing that below-the-tracks spaces are almost always only valuable in situations (I’m thinking in Ginza, the Viaduc des Arts, or 9 de Julio) where such space is just the cheapest way of getting valuable ground-level, street frontage. Even maglevs are pretty awful to stand right underneath.

Besides, haven’t we tried grade-separation of different modes before?

3. NAIOP recently published a report offering slight encouragement to the notion that office users are increasingly choosing mixed use environments — namely, 24-hour CBDs and 18-hour “suburban vibrant centers” (their terminology, not mine) — over single use suburban office parks. Their findings indicate that rental rates are indeed higher in CBDs, but that CBDs haven’t seen as much absorption as suburbs, whereas “vibrant” parts of suburbs had a verifiable edge in the leasing market. There’s certainly plentiful anecdotal evidence, and this has been the mantra of “Emerging Trends” and other qualitative reports for quite some time, but I’ve seen few attempts to quantitatively analyze the phenomenon.

Yet the two sets were compared quite differently. The comparison of CBDs vs. suburbs was strictly quantitative, an approach that didn’t control for the quality of the urban environments — downtown absorption was hurt by including a great many “dead” downtowns (Dayton, St. Louis, Hartford) among the comparison set. Most of the liveliest downtowns have seen strong positive absorption, since it’s less the CBD location than the mixed-use amenities that draw users.

The “vibrant centers,” on the other hand, were compared using a robust paired-case approach: single-use suburban areas were paired with mixed-use suburban areas within the same part of town. They even came up with a pretty strict definition of such centers and their comparison sites, using Walk Score and building-level maps. This better methodology dives into why people are migrating towards such sites, and goes beyond the not-terribly-nuanced submarket definitions found in typical office market reports.

Although the lower absorption figures for CBD office may look discouraging at first glance, it’s necessary to consider both that higher rents might result in tenants using CBD space more economically. Square feet don’t necessarily correspond with people, much less dollars. (Edit 26 Feb: City Observatory has a new report indicating that job growth has indeed been more robust in CBDs than in suburbs.) In addition, the supply constraints on new downtown office might suppress demand from space-hungry users — e.g., many large companies are expanding both in San Francisco and Silicon Valley, but adding more jobs in the Valley where construction isn’t limited by constraints like Prop M.

4. For good measure, here’s one instance where the methodology and the results both turned out okay: Governing’s recent analysis of gentrification at the Census tract level. The scale of the analysis is correct, the results pass the smell test, and the variables used (rankings of changes in household income and physical [home values] and cultural capital [college attainment]) seem reasonable.

A few more thoughts on beautiful Brutalism

Board formed concrete

Writing “The five best Brutalist buildings in DC” required a lot of attention to definitions. The article’s less about the “best” Brutalist buildings than about examples of Brutalism that fit in well with their urban surroundings (or, in one case, rural surroundings). I love the Hirshhorn Museum’s courtyard, for instance, but it’s pretty awful towards everything around it, so it didn’t merit a mention in the article.

That said, I did check each of the buildings against Reyner Banham’s original 1955 article on Brutalism, which established these three criteria:

1, Memorability as an Image;
2, Clear exhibition of Structure; and
3, Valuation of Materials ‘as found.’

If any of the seven buildings are “on the cusp” per Banham, the CFPB and Canadian Embassy fit in too well with the perimeter-block typology of the city around them — and therefore don’t quite have the cartoonishly simple standalone imageability* typical of the Brutalist sculpture-as-building. Yet both are very clear in plan and intent and have imageable elements. Perhaps the Canadian Embassy’s devalued materials make it more of a postmodern spin on Erickson’s own Brutalism, but that’s a fun tautology.

Commenters have disputed Dulles Airport’s inclusion, perhaps because they actually like it and want to reserve “Brutalism” for stuff they don’t like. Yet it easily meets Banham’s definition, and furthermore celebrates a vast expanse of béton brut like no other local structure.

Other links I wanted to include, but that didn’t quite fit:
– Sometimes, even a clumsy Brutalist building can be better integrated into the urban fabric through changes to landscaping and circulation; such repairs are underway at Boston’s City Hall.
– Over in supposedly kinder Ottawa, Brutalism was the house style for many cultural institutions, and insensitive changes to these buildings are proving controversial.
– The BBC is currently airing a two-part series on Brutalism.
– Some very highly expressive concrete canopies are on view now in an exhibit at the Art Museum of the Americas about the work of Félix Candela, whose soaring but paper-thin concrete shells enclosed everything from bandshells to cathedrals throughout Mexico.

* Favorite story about this: A cab driver in Shanghai didn’t know which Hyatt hotel I wanted to go to. Instead of fishing around for the address, I drew the shape of the building, and we were off. (It turns out that “Hyatt” was Sinicized in Cantonese, perhaps because the chain opened in Hong Kong before China, so when written in Mandarin it’s pretty much gibberish.)

New steel & wood innovations that make mid-rise construction easier, faster, cheaper

Earlier this year, I wrote about some new materials and techniques that could make structural engineering for mid-rise buildings easier, faster, and cheaper. If widely implemented, these could make human-scaled mid-rises more affordable, more widespread, and frankly better looking.

ConXTech

Steel makes elements like this penthouse easier to build. (Alas, the exterior’s been toned down from this glassy early rendering.)

1. While I was in California, I saw two examples of steel-framed mid-rise buildings constructed using ConXTech, an Erector Set-like approach to steel frames that promises to save time and money through computer-aided prefabrication. Eddie Kim writes in the LA Downtown News that the Eighth & Grand grocery + apartment building, “There’s no army of welders diligently fusing each joint and beam. Instead, steel girders are being lowered and snapped into place.”

Dan Garibaldi from developer Carmel Partners told Kim that the technique cut costs some, but really saved time and added design flexibility, particularly crucial in a mixed-use project: “We contracted for the steel at a beneficial time so the cost differential is not nearly what it would be today… The main benefit is how quickly we can complete the framing. In addition, ConXtech allowed us [to build] an additional residential floor and create long spans that are not easily achievable in wood frame.”

ConXTech co-founder Robert Simmons expressly invented the system to compete with Type III-over-I construction. He told Kim, “we were looking at ways to create a competitive method of structural framing versus wood and I couldn’t do it with concrete, so I started looking at steel.” His firm worked on the concrete retail podium at Santana Row in San Jose, which suffered a massive construction fire — not unlike recent fires that destroyed under-construction, pre-fireproofed Type III buildings in Mission Bay and on Bunker Hill.

Santana Row

Not Type III over I.

Santana Row’s upper-story apartments (and hotel) were rebuilt using ConXTech steel, and there are palpable differences between it and, say, Rockville Town Center (another Federal Realty development, built as conventional III-over-I), notably more generous window openings and a subtler transition above the podium. At Santana, the base of the building often extends above the second floor, allowing not just for retail mezzanines but also adding vertical articulation.

2. Cross-laminated timber is a particularly exciting new technology for D.C. buildings: under current building codes, it can reach up to 90′ high — the height limit outside of downtown — and uses wood, which is locally available, easy to work with (i.e., fast and inexpensive), and has a comparatively small carbon footprint. Plus, it can look like the old timber lofts of yesteryear, a building type I’ve long been fascinated with.

Architect Michael Green’s Wood Innovation and Design Centre in Prince George, B.C. was recently completed; it reaches 90′ with its eight stories — or, technically, five stories and a penthouse over a one-story podium with a mezzanine, a bit of creative accounting perhaps done to satisfy code requirements. But whatever, Prince George might as well be on the moon, since it’s 500km from even Edmonton or Vancouver.

A heavy timber loft for the 21st century, built with rapidly renewable materials.

What’s more notable is this seven-story speculative office building that fits right into downtown Minneapolis’ loft district, designed by Green and developed by office titan Hines. Sam Black writes in the Business Journal, “Unlike Warehouse District buildings such Butler Square and Ford Center that were built out of huge logs, modern timber buildings use wood engineered from several layers of younger trees.

Today’s office tenants disdain boring concrete high-rises, and even the new-construction concrete “lofts” that began popping up in the 2000s are a weak alternative. CLT offers architects a chance to build an authentic timber loft building, from scratch, and without harming old-growth trees. Bob Pfefferle from Hines told Kristen Leigh Painter of the Star-Tribune, “it provides an authentic building that is respectful of the neighborhood. This will have the ambience of the old warehouses with timber beams that everyone wants, but solves all the problems of energy efficiency and light.”

Coincidentally, this month’s Arch Record has a sponsored feature on “tall wood” buildings. The IBC, it points out, limits commercial-occupancy wood buildings to six stories (vs. five for residential), hence the seven stories that Hines is proposing.

I can imagine that similar new-build loft offices could be popular in similar downtown-adjacent submarkets, and transformative for Sunbelt cities where sparse “warehouse districts” have little competing product. I’m thinking Austin, Denver, Raleigh, San Diego, Seattle, or maybe infilling Bay Area subcenters like West Berkeley and Redwood City

Building type survey: stacked flats in Norfolk

A quick trip to Norfolk last weekend turned up at least one pleasant surprise: a tradition of Chicago-esque stacked flats apartment buildings, here in the rowhouse-heavy Mid-Atlantic. Many were around the Ghent neighborhood, primarily along higher-traffic (probably former streetcar route) streets like Colonial Ave. and Hampton Blvd.

The neighborhood’s lots are a fairly generous 30′ wide, so a double lot can easily fit narrow courtyards between three-story stacked flats:

Ghent, Norfolk

More common, though, were double-lot six-flats — with deep neoclassical porches, reflecting the fact that they are, after all, in the South:

Ghent, Norfolk

Just as surprising was this liner apartment building, apparently built in 2006 at the corner of Colonial and Princess Anne to mask a 1970s-era serrated senior housing high-rise. The porch detailing is a bit clumsily done — the building is too wide and shallow to match to the six-flats’ columns across the street — but the building holds a busy corner much better than whatever parking lot or open lawn that preceded it. Similar proposals have been controversial even in New York City, so it’s heartening to see a fairly good example.

Ghent, Norfolk

The Chicago six-flat is a particular adaptation to several factors: fairly wide (25′-28′) lots, readily available brick, and a fire code that both largely banned party walls and required two exit stairs. They’re readily identifiable from a front stair off to the side, leaving space for a spacious “front room,” and exposed “back porches.” True to form, the Norfolk houses also had exposed rear exit stairs, even in the absence of alleys.

Alas, the city’s pattern books don’t have much to say about the type.

Telematics can reinforce centralization

Self-valeting vehicles would make going downtown a lot cheaper and easier. Photo: Steven Vance

1. Telecommuting is great, but only to a point. According to Gallup, “the ability to work remotely corresponds with higher engagement, but primarily among those who spend less than 20% of their total working time doing so.” Employees who spent more than 50% of their time working remotely had engagement and disengagement figures similar to those who never worked remotely. (The release also has some nice quotes from Vint Cerf at Google about the value of face-to-face interaction, and how they’ve sought to increase collaboration within the workplace.)

2. On a similar note about the potential of telematics, there’s a lot of hype out there about autonomous vehicles, aka driverless cars, but Nat Bottigheimer and my former colleague Brooks Rainwater have appropriately measured responses.

In the few conversations I’ve had with transportation professionals about their impact, their understanding is similarly muted. Yes, platoons of autonomous vehicles will squeeze a little bit more capacity out of existing roads while maintaining laminar flow, but it’s not as if there’s scads of peak-hour capacity remaining to be had.

The really big impact will be upon parking. By removing the cost and hassle of parking at the final destination could make urban centers even more valuable, and further diminish the primary appeal of drivable (really, parkable) suburbia — which is that it’s easy to drive to, and park at. If both of those factors become immaterial, then why bother driving to the B-mall when you could go straight to the A-mall, or downtown?

Similarly, an interesting class divide could arise if the vehicles really do succeed in eliminating driver-error crashes. Such crashes could soon become stigmatized as something that only happens to poor people who can’t afford fancy crash-avoidance technology. (Do people today cluck-cluck with resignation about people maimed in car crashes because the inexpensive cars said victims bought used were not equipped with adequate airbags?)

Planning’s fruits include Shaw’s Progress(ion Place)

Progression Place

Eight years on, the District seems to have gotten a nice return on its $20 million investment into Progression Place, the long-awaited development that replaced a city-owned parcel above the Shaw Metro that some called “the block of blight.” Not only has the Mid-City neighborhood gained an employment anchor (DC’s grants went to the office portion) and 50 units of affordable housing, but Progression Place also created a lively block of walkable retail that complements DC’s adjacent investments in the Metro and the Howard Theater. So yes, although you may have to wait a while, sometimes city plans do eventually work according to plan.

From a planning perspective, Progression Place features a broad mix of uses at a fairly high intensity:

  • It anchors a new uptown office district, with 100,000 sq. ft. of new offices being built now for the UNCF and Teach for America. Next door, the Wonder Bread factory has another 98,000 feet, for a combined daytime population at lease-up exceeding 1,000. It’ll be interesting to see who moves in here; even beyond the Digital DC initiative focused here, TFA is known as having a younger constituency than most other federal programs. Although the Green Line has spurred great residential and retail growth, its potential for office is rather less tested.
  • 205 apartments; 1/4 inclusionary, with both low and moderate income price points.
  • The retail tenant mix has a few nationals (Bank of America and Sprint) alongside several established local operators, led off with a critical mass of food & beverage destinations. The merchandising by StreetSense is also first-rate, and not only because I’ve a known soft spot for beer, bakeries, and tea. Having great retail in place (and thus a high Walk Score) will help residential leasing. I suspect that retail is somewhat of a loss leader here, which might explain why the retail and residential are under one owner.
  • There’s underground parking, but the overall parking ratio is about 0.57 spaces per 1,000 sq. ft., shared with the historic Howard Theater next door. A comparable project in the suburbs might include 4-5 times as much parking.

Just as importantly, the building’s architecture pulls off the “vanishing high-rise” trick quite well by setting the tower 35′ behind the storefronts. What could be an overwhelming slab of an apartment building — with a net density of 301 dwelling units per acre, excluding the site’s office and T Street wings — disappears at street level behind the historic row of storefronts:

Progression Place Storefronts

The 19,500 sq. ft. of retail is almost entirely housed behind retained and rehabilitated historic storefronts, retaining not only their appearance but also the fine-grained scale — i.e., the neighborhood’s classic rhythm of narrow lots and small bays. The original finishes, like exposed brick, carry through to the interior — but behind the front room, modern new building services are provided in the back of the house, as part of the new structure. This transition (visible in the retail floor plan) is subtle enough to have evaded notice by at least one table of architects I was dining with.

In some respects, this project probably benefitted from having local firms in charge of development and leasing, including layering a complex capital stack, and then selling the property on to a national income-oriented owner. Four Points’ next project might well be downtown Anacostia, a site they’ve been waiting on for several years.

Disclosure: I have no financial interest in any businesses or properties named, or located on named sites.

[Blogging update: now that I’m working at Streetsblog, I might be able to repost some pieces from there, and will continue reposting items cross-posted to Greater Greater Washington or written for other venues.]