How green is your skyscraper? Why the most sustainable buildings might be low-rise

Well, this one's pretty green. The Empire State Building, in its St Patrick's Day gladrags. Image: Getty.

The fact a controversial cornucopia of towers is coming London’s way is well known – and some who support this development claim that towers are “greener” than low-rise living.

But are they? My new research project at UCL’s Energy Institute (conducted in association with Create Streets) will try to discover if high-rise buildings are more energy-intensive than equivalent low-rise buildings. At present the evidence is uncertain, but there are suggestive hints. We intend to test them.

Many variables can affect tall buildings’ energy use – and only some of them relate to height. There is the use of energy in lifts. There is the use, or not, of air conditioning. There can be important differences due to building construction, especially between glass curtain walls and solid walls, since rates of heat loss are greater through the glass. Finally, there will be effects related to the local environments of buildings – such as orientation, overshadowing and exposure to sun and wind.

There is some evidence on the relationship between height and energy use. A 2003 study of 20 comparable Hong Kong office towers found that, as high increased, there was a steady increase in energy too. Each additional storey added on average 3 kilowatt hours per M2.

But the use per M2 for lighting and – perhaps surprisingly – lifts did not increase with height. The biggest increase was in the energy used for heating, ventilating and air conditioning. The Hong Kong climate is hot and steamy: we would expect heavy loads for air conditioning. But these were greater, per unit of floor area, the taller the building.

The energy element of the English Housing Survey provides evidence of the relationship between energy use and height in tall residential buildings. A preliminary analysis of data on both low- and high-rise purpose-built flats shows that the latter use on average more than twice the amount of electricity annually (although the sample is small).

That said, there have been studies that have shown little or no difference in energy use with height. Aedas Architects analysed theoretical designs for tall office buildings, using simulation models, and found only small increases in energy intensity with height.

Researchers at the LSE carried out a study of energy use for heating in residential buildings of many different types. They found that energy use decreased with height. However, they too were working with simulations. Furthermore, their sample only included buildings up to 11 storeys.


Why might we expect energy use to increase with height? The obvious characteristic of tall buildings is that they stick up above their neighbours: they are exposed to higher winds. Data from the Chartered Institution of Building Services Engineers shows that wind speeds do indeed rise with height

And higher winds can contribute to increased energy consumption in several ways. They remove heat from the surfaces of buildings. They increase drafts, meaning that the air inside requires more heating or cooling. And they can increase the rates of conduction of heat through the building’s envelope, especially through glazing. Tall buildings tend also to be more exposed to the heat of the sun, and are less likely than low-rise to be overshadowed by trees or other buildings. This can lead to increased energy requirements for cooling in summer.

It seems at least possible that such effects are insufficiently represented in the simulation models used to estimate energy consumption during the design of tall buildings. This could lead to underestimates of predicted energy consumption in practice.

It’s sometimes suggested that a concentration of tall buildings around public transport hubs can help shift travellers from cars to buses or trains, and so reduce energy consumption in transport. This may be true. However, it is an argument for higher densities rather than skyscrapers, as such.

Some researchers have looked at the potential for “green” retrofitting of existing tall buildings. Valuable as this work is, it seems possible that most, if not all, of the conservation measures and renewable technologies employed in “green” or low-energy skyscrapers could equally be applied – perhaps with greater effectiveness – in low-rise buildings. One could also imagine that the potential for adaptation and refurbishment would be greater in low buildings than in tall ones. Might the most sustainable skyscraper not be a skyscraper at all?

Philip Steadman is professor of urban and built form studies at University College London. This article is adapted from an essay he wrote for Create Streets.

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Vanilla Skybus: George Romero and Pittsburgh’s metro to nowhere

A prototype Skybus on display near Pittsburgh. Image: BongWarrior/Wikimedia Commons.

The late director George A Romero’s films are mainly known for their zombies, an association stretching from his first film, 1968’s Night of the Living Dead, to his last as director, 2009’s Survival of the Dead.

But many of them are also a record of Pittsburgh, the city he lived and worked in, and other locations in the state of Pennsylvania in the late 20th century. Martin (1978), for example, isn’t just a movie about a kid who thinks he’s a vampire: it’s a moving portrayal of the post-industrial decay of the Pittsburgh borough of Braddock.

Though born in New York, Romero studied in Pittsburgh and stayed in the city after graduation, shooting commercials as part of the successful Latent Image agency. It was in collaboration with advertising colleagues that he shot his debut Night of the Living Dead. On both that movie and subsequent films, Romero and his colleagues used their experience and connections from the agency to secure cheap and striking locations around the city and state. 

It’s in Romero’s little-seen second film, 1971’s romantic drama There’s Always Vanilla, that a crucial scene touches on a dead end in the history of urban transport in Steel City.

In the scene Vietnam vet Chris, only recently returned to town after a failed music career, sees his father off on a train platform, after an evening where Chris got his dad stoned and set him up with a stripper. (It was the early 1970s, remember.) An odd little two-carriage metro train pulls up on an elevated concrete platform, Chris’ father rides away on it, and then Chris literally bumps into Lynn, whom he then both gaslights and negs. (It was the ‘70s.) You can see the scene here.

A screenshot from There's Always Vanilla, showing the Skybus through a chain link fence.

If you don’t live in Pittsburgh, you might assume that funny little train, still futuristic forty years on, is just an everyday way of getting around in the exciting New World. Who knows what amazing technology they have over there, right?

In fact, the Transit Expressway Revenue Line, more snappily referred to as the Skybus, not only doesn’t exist today: it hardly existed at all, beyond what we see in that short scene. In the 1960s there were plans to replace Pittsburgh’s street car system with a more up to date urban transit system. The Skybus – driverless, running on rubber tires on an elevated concrete track with power provided with an under rail system – drew enough support from the Port Authority and Federal Government for them to fund a short demonstration track at the Allegheny County Fair, at that point a local institution.

It’s this demonstration track and train that appears in There’s Always Vanilla. Film makers love isolated systems like this, or the UK’s many heritage railways, because they allow for multiple takes and a controlled environment. So it made sense for Romero to use this local curio rather than seek access to an in-use station.


The sequence in Vanilla shows that the Skybus system worked, and as a potential metro system it looks quite striking to this day with its curved windows and distinctive logo. But the proposed system wasn’t popular with everyone, and cost concerns and political wrangling stalled the project – until it was finally rejected in favour of a more conventional steel wheel on steel rail transit system.

The demonstration track was pulled up in 1980, although the small station and platform seen in the movie remains: Romero expert Lawrence Devincentz narrates a photo tour of the building on the blu ray of There’s Always Vanilla.

Vanilla was renamed and barely seen on release, but is now available as part of a boxset of Romero’s early works from Arrow Video, in ridiculously pristine 2K digital transfer. The Skybus is there too, a curio of Pittsburgh history caught on a few short minutes of film. Neglected back then, both seem considerably more interesting now.

‘There’s Always Vanilla’ is available on blu ray as part of Arrow’s ‘George A. Romero: Between Night and Dawn’ box set, and will receive a standalone release later this year.

Mark Clapham used to work in rail regulation, but now writes things like this. He tweets as @markclapham.