My tweet-cast of Léon Krier's address to the Congress for the New Urbanism Saturday morning created a small firestorm for a while on Twitter characterized by @nlamontagne's "Low-rise fetishism is bad for cities" and @BLAH_CITY's iconic "...my coffin will be "human scale"! All else is architecture..." Never mind that the real fetish here is the Skyscraper Fetish. In any case, here are several thoughts for the skyscraper apologists:
Sustainability may be defined as "keeping things going in a healthy way, long into an uncertain future." That uncertain future is very unlikely to include cheap energy at levels we know today. At unaffordable energy price levels, what fails to work in high rises?
1. Wind speed increases with distance from the ground. A gentle breeze on the ground translates to something closer to a gale higher up. Open two windows for cross-ventilation on the forty-second floor, and all your papers may get blown out into the street. That increased wind speed, when combined with rain, plays havoc with weatherstripping in operable windows. Operable windows in high-rise offices therefore have serious issues. But on a hot day without cheap fossil fuel, inoperable curtain walls have an even bigger problem: without the ability to cross-ventilate, the building may literally be uninhabitable because without a way to dump excess heat, interior temperatures would soon become even hotter than outdoors.
2. Our great-grandchildren will ask "what were they thinking?" about many of our building techniques. Chief amongst them will be glass curtain walls. The best possible curtain wall today is not as good an insulator as a 2x4 wood stud wall, R-11 fiberglass batts, and the cheapest possible finishes. Yet we wrap all four sides of buildings (including east and west sides, facing the hot, low sun) with the stuff, acting as if the laws of thermodynamics don't exist. But as energy costs climb towards the unaffordable, glass-clad high-rises will move closer towards being uninhabitable.
3. We sun-screen our curtain walls to a high percentage because if you're sitting near the curtain wall, the glare through clear glass would be far too strong to work comfortably. But the sun-screening cuts down on the light that's able to reach deeper into the space, so only those workstations right on the window have good daylighting. Interestingly, the screening percentage often allows close to the amount of light you would get if you put traditional windows in the wall because they only occupy 15-25% of the wall.
4. In most moderate climates, passively-conditioned buildings benefit from exterior walls with thermal mass, a property almost completely missing from glass curtain walls. Unfortunately, high-rise buildings cannot be retrofit with massive walls because the building structure would not support the many tons of additional weight. This, combined with the issues above, mean that glass-clad buildings that cannot be retrofit will be uninhabitable in a period of unaffordable energy costs.
5. The towers of large buildings built before air conditioning were shaped like letters so that no wing was more than 30 to 40 feet wide. They daylit beautifully. With transoms over doors to the hallway, they cross-ventilated nicely as well. Most high-rises have floor plates far in excess of 40 feet in their narrowest dimension, meaning that only the corner offices cross-ventilate and only the outer offices daylight. The bulk of the floorplate would be uninhabitable in a period of unaffordable energy costs.
6. Elevator motors consume more energy than any other single piece of equipment in a high-rise building. In a period of unaffordable energy costs, people would only be able to occupy floors as high as they could physically climb. For most people, that limit is a climb of 4 or maybe 5 flights of stairs, resulting in a city that looks much more like historic London, Paris, or Rome than Manhattan or Vancouver.
I appreciate the well performed architectural analysis, and I don't disagree, in a non-affordable energy market that might be a problem. Unfortunately your story doesn't denote that there is no such thing as unaffordable energy. There is unaffordable fossil fuel, but there is actually a very nice normal cost per oil barrel equivalent for renewables that are reliable if combined and diversified along with a typical back up battery bank, this cost is typically noted as 130 to 150 dollars per barrel of equivalent oil.
So while energy costs are skyrocketing there really is no fear that no one wil...See More
If you heard Léon Krier at CNU Saturday, this is my response to his comments on high-rise construction. What do you think?
WE NEED an Original Green short conference with Clay Chapman of Hope For Architecture so he can present his $80 psf masonry house metric and methodology...i was at ND crits and discussed this and the school is thinking of hosting him so it may be a good mutual event...
Steve, many good points here, but since you've called me out, I feel compelled to add my perspective. And while some of these issues really do need to be addressed (especially the prevalence of the glass curtain wall and the excess exterior glazing popular in the Vancouver-style residential tower), I still stand by my point about mid-rise fetishes and don't buy the apocalyptic anti-tower argument.
Its true that towers consume a lot of energy - and we need to be hyperaware of the intricate interrelationship of building and energy - but they also house a lot of people or a lot of economic activity. In fact, as I know you appreciate, almost all buildings consume a lot of energy and generally, the lower the density, the higher the per-capita energy use. And towers do rely on some energy-intensive systems, although elevators are pretty much a drop in the bucket. Sure they may be high as a single-piece of equipment, but most modern elevators use counterbalance and have energy recovery systems on descent (much like a prius). The big culprits in most large buildings (high and mid-rise) is the underground parking (lit, conditioned, and ventilated 24-7) and, of course, heating and cooling. Indeed, line losses from recirculating hot-water are likely to be a much larger energy loss than elevators. (also, for a city like Vancouver, we don't need to worry as much escalating energy costs making high-rises uninhabitable because the elevator won't run. Don't forget, most of those elevators in a Vancouver tower run on hydro-electricity. Not ideal and we must always be vigilant about any energy use, but calm down on the speculative hyperbole).
High-rise towers are not for everyone and certainly not for everywhere, but from my perspective, they have to be in the toolbox for any serious urbanist. Towers enable a lot of design options that work for many sites in the city. And, quite frankly, if we are going to develop the kind of dense, complex, urbanism that we need for a green urban future, the high-rise (above 12 storeys) can make that work much better. There are many benefits to tower urbanism (as part of a complete mix of building types and housing choices in the city). Due to their economy of scale, towers enable more innovative design features and often much more developed public realm solutions (indeed, in Vancouver, almost all towers require a rezoning, which in turn requires LEED Gold certification - which the economics of towers makes easy to do. Not to say that LEED is ideal, its not, but its a key step in Vancouver's carbon-neutral building strategy). And towers enable more sculpting and terracing (the Australians have done a great job balancing indoor/outdoor space with their towers). And because of the density and public realm that towers in Vancouver have enabled, we've seen some big wins for sustainable urbanism. Our per-capita carbon footprints in central Vancouver (1.5 tons/per person) is the lowest in North America, vehicle traffic is way down in the downtown (20% from 1996 to 2011), and over 75% of residents walk to work. Find me a mid-rise neighbourhood in the US that has delivered that kind of shift from the car. And its by living in smaller spaces and traveling by walk/bike/bus that will really hedge our future against the real escalation of energy costs. Density by itself is never the solution, but 'density done well' is, and towers can be a part of that.
My concern is the obsession with mid-rise as a way of 'sneaking in' density. I see this a lot in California and the result is horrendous. Bulky, cheaply constructed, perimeter block buildings with poor indoor/outdoor relationships. And the reality is that in most North American cities, it is a challenge to develop the kind of intricate large-scale low/mid-rise neighbourhoods that could deliver the kinds of densities that we need to enable a more sustainable urban future. Allowing cities to rise up past the 6-storey cornice line at key places is a smart solution. So I say forget the mid-rise fetishes and embrace smart design of high-rise urbanism. Its part of the big picture.
BTW, the last plan that I did at the City of Vancouver (I was a planner there, hence the many Vancouver references, before beginning my PhD in Urban Planning at UCLA), explicitly embraced both taller buildings (although not above 12 storeys) and a new zone that emphasized the 'alphabet buildings' that quite frankly are almost never developed anymore. This was not a central city neighbourhood, so the building heights are low, but I still believe in the tower as part of my urbanist toolbox. I am as much a fan as mid-rise density done well as I am high-rise. But never one at the absolute exclusion of the other.
Love the blog and your work - keep up the good fight!
Though you argue against the tower as a typology, most of the article criticizes particular design issues. There is nothing wrong with building tall, provided it is done thoughtfully. Poorly executed low/mid-rise development is no better.
If you're going to predict the future costs of energy, consider also the future costs of land, materials, etc. It would be interesting to see a thorough analysis of the cost of building and operating a highrise vs. low-rise.
How expensive do you expect energy costs to get exactly? Wind and solar might be a bit more pricey then coal but AC will still be cheaper then it was decades ago.
Good points, indeed. Yet the state of the practice in highrise design is to make use of solar, wind, natural ventilation, etc., getting away from the big, sealed mechanical box models. There are buildiings going up today (not in the US, alas, that use these principles to drive energy costs down by 70-80% while delivering superior comfort and adaptability. The challenge will be to get that kind of intelligence across whole markets, instead of in a few trophy buildings.
Your point about wind speeds increasing dramatically as the height increases showcases the opportunity for wind energy. I have seen a couple of buildings incorporate windmills into the design. Why is this not a bigger trend? Wouldn't a massive windmill be more effective and efficient than a large spire?
I have to agree with Neal on one point, the sustainability cost of parking for high-rise.
I think if there is one area planners could focus on would be that once you hit a certain number of floors, a solid transit system should be in place and auto parking greatly limited.
Such a model would encourage a complete transit network as people without cars in posh buildings do now want to be limited to a bar or two of rail grid. As well it would encourage modest height urbanism where transit is not yet online.
That said when you look at the way high-rise buildings were swapped pre 2008, I think few cared about the cost of maintaining a building, it was all about appreciation in value. I think that has greatly changed with much lower profitability on owning/leasing/building of the high-rise. As maintenance cost becomes such an issue, and many companies are seeking a green profile, the expensive to maintain high-rise begins to look more and more risky to investors.
Also with much more high-rise residential being built those costs are passed directly to the consumer, who tends to price compare with other styles of urbanism. It is not hard to compare condo-fees and utility bills in residential.
Long before we can't afford the elevator I think the push for mid-rise will be driven by competitive cost issues, and then as that push creates better urbanism and transit, it will become more of a quality of life issue where people choose a healthy scale of urbanism because of the overall environment, culture, character of place.
As well modest scale urbanism will substantially reduces the risk for investors and developers as each project has a much smaller financial footprint, making constructing financing more realistic for many.
I think the high-rise will more and more be seen as a downtown novelty, or a place for those with a lot of cash to burn.
Assuming we don't return to 2005 financially, which now seems quite doubtful, these cost issues should create a lot of pressure to build much more sustainable urbanism, dense enough to be interesting and functional for transit, and light enough to be more affordable.
Thus Steve, everything you describe in your post should already be very relevant to the smart developer/financier.
This will be an interesting project in the US to follow. The challenge will be to get transparent performance results...
Have you read Cities for People by Jan Gehl? The reason I mention it is that Gehl also makes a good case against high rises. He argues that high density by itself does not bring about liveliness, and points to a couple of studies that suggest low rises have more street life per capita.