The End of the Age of Tall Buildings


Vancouver towers from Wikimedia Commons

[Update: see post on this topic on the Vancouver Lights blog. Also see this critique of glass highrises by Lisa Rochon in the Globe and Mail.]

Apologies that this is such a long post. For urbanist nerds only, perhaps, though this issue affects anyone interested in urban affordability

The other evening I had to go to a meeting in a condo tower’s boardroom. I left the building at dusk and found that I couldn’t orient myself. I was with a friend and we actually stood there in the windy canyon between glass towers trying to figure out which way we were going. We oriented ourselves after a minute but were left with the impression of a confusing, generic, bleak, pedestrian-free dead zone in which the only moving objects were cars. And this was on a dry, balmy late September night! I cycled home and ten minutes later found my own neighbourhood alive with people still out walking and talking at 9 pm.

The worst part is that these generic glass towers—which are being erected all over town and steadily damaging neighbourhood life and texture—are not fully inhabited. Realtors have been warning us for some time that a large percentage of condos are owned by absent non-resident investors (probably both local and foreign). We await studies of hydro/electricity usage to prove this, but it’s almost certain that there is an element of property speculation in the tower business.

Now it turns out that on top of the aesthetic problems and the property speculation, the towers aren’t even green. This is pretty egregious considering that their “sustainability” has been their main political justification at City Hall over two different administrations.

Why are we still letting developers build condo towers, exactly?

The excerpts below are from Adapting Buildings and Cities for Climate Change: a 21st Century Survival Guide (2nd Edition, 2009) by Sue Roaf, David Chrichton, Fergus Nicol. It was published in 2009 and I’m told is internationally regarded as the most comprehensive and authoritative study of this topic to date. It is described at http://www.downarchive.com/ebooks/260105-adapting-buildings-and-cities-for-climate-change.html and can be downloaded free of charge here.

My interest in this topic is motivated by what I see happening in Vancouver where the newest architectural style is something I just call “Tall Naked Capital.” A new shadow-throwing, wind-producing towers do damage to the quality of pedestrian spaces in this city, not to mention all the other effects such as sterile streetscapes, failure to fit in with existing historical architecture, community patterns and existing cultures, as well as raising local rents and property prices. The main beneficiaries of towers seem to be the mega-developers who build them. What’s most disturbing is the unexamined notion that these buildings, due to their density, are “green.” What is green about them, and does their dense stacking of humans really outweigh their non-green impacts? Are they really green or have developers merely disseminated that myth? Vancouver has always been dominated by powerful developers, who, by the way, have built virtually no great buildings in 30 years, have recently tried to ram a downtown mega-casino down our throats, and are generally working against the best interests of the city and its inhabitants by helping to drive up land prices.

The chapter below makes interesting reading. Introduction to this topic by a friend of mine:

“Apparently the University of BC’s School of Community and Regional Planning SCARP “Urban Studio” project has used this and other sustainability research to demonstrate that Vancouver could meet extremely aggressive  growth demand projections for about the next half-century, without further upzoning (or spot rezonings) for highrises in the West End, Heritage Districts, or Downtown South, through the use of low-rise and lower mid-rise building forms that are consistent with existing Local Area Plans and City Plan Visions. For an earlier draft of this (supplied by Patrick Condon) see http://www.urbanstudio.sala.ubc.ca/2010/book%20templates.html .

This is primarily accomplished through build-out of existing mixed-use (C2) zones and moderate extensions of these zones along arterials presently served by transit. With rate-of-change and inclusionary rental polices, and increased DCLs (to lock in funding for public amenities), such incremental, iterative redevelopment would protect and provide relatively “affordable” housing (“core-need” requires senior government funding), and a sufficient increase in retail and services for the expanded population in walkable neighbourhood centres, respecting and protecting human scale, neighbourhood character, public views, access to sun and sky for homes, gardens and the public realm through the use of building forms that are inherently “green”—unlike the highrises and mega-towers for which the big developers have been lobbying Council. In fact, the rezoning policies and spot rezonings that these developers, city staff and Council have been relentlessly pursuing (not only downtown, but in Marpole, Norquay, Mount Pleasant, etc), undermine the neighbourhood-based CityPlan paradigm (which, ironically, is essentially “greener” than many of the greenwashed, developer-driven EcoDensity/Greenest City land-use policies), by diverting development to these less sustainable and generally more problematic large-scale options.”

THE END OF THE AGE OF TALL BUILDINGS

The age of skyscrapers is at an end. It must now be considered an experimental building typology that has failed. With the arrival of the global economic slump in 2007/08, so began the end of the age of tall buildings. We wrote of its imminent demise in the first edition of this book and since then the prediction has come true. The reasons we gave in 2003 and what has happened since, are covered below in a review of the phenomena that must constitute the twentieth century’s greatest‘ follies de grandeur.

SPACE PLANNING PROBLEMS

A high-rise building usually consists of a shaft and elevators surrounded by living units on each storey. The properties of openings in the south (sun: solar gain) and north (cold wind: infiltration) and the very limited opportunities for the floor plans, with restricted walk distances to fire exits and access shafts, drastically reduce the organizational possibilities of the plan.

The form also has climatic design limitations, magnified because they occur on every floor in a rigid plan form. It has been proven nigh on impossible, for instance, to prevent all south-facing apartments in high-rise buildings from overheating in summer and all north-facing ones being cold in winter due to radiant gains and losses.

TOO EXPENSIVE TO BUILD, OPERATE AND MAINTAIN

However, there does seem to be a virtuous circle that is operating that is making people aware that you simply can’t have ‘green towers’ because they use too much of the Earth’s rapidly dwindling raw materials, they cost too much, their impacts are too great for small areas and in most cases they don’t retain their value as well as, or for as long as, lower less polluting buildings. The higher the building, the more it costs to build and operate, and the more costly and difficult it is to maintain.

The primary increase in build costs, per metre square, results from the increased structure and construction required to support the building, to earthquake-, fire-and weather-proof it, and the increased systems needed to operate it, including lifts, escalators, water pumping and electrical systems. These high costs can only pay back if higher than average prices are paid for the floor area, housing or offices than would be the case in a lower rise building.

Table 12.1 Results of a study of the embodied energy of buildings showing that the taller they are the more energy is embedded in them per metre square during construction. The case study buildings in Melbourne, Australia, show embodied energy results in GJ/m 2 gross floor area by element group 

Height in storeys        3     7     15     42     52

Structure group          5     7      9.9  11.7  11.6

Finishes group           0.6  0.4   0.5   0.4    0.7

Substructure              0.9  0.4   1.2   0.5    0.7

Roof                           1     0.8   0.1   0.2    0.4

Windows                    0.3  0.2   0 a   0.2    0.1

Non-material group   2.9   3.2   4.4   4.9    5

Total                        10.7  11.9  16.1   18    18.4

 

In addition, the higher the building, the more it costs to run because of the increased need to raise people (lifts), goods and services and also, importantly, because the more exposed the building is to the elements the more it costs to heat and cool. The higher the building, the higher the wind speeds around the building, the more difficult to keep the wind out, and the more the wind pressure on the envelope sucks heat from the structure, particularly as with many twentieth century tower blocks the envelope leaks. The higher the building, if standing alone, the more exposed to the sun it is and the more it can overheat. And hence the higher the building the more it costs to keep the internal environment comfortable. Lifts are very energy expensive and costly to run, maintain and replace. Lifts alone can account for at least 5 – 15% of the building running costs and the higher the building, the more it costs.

The higher the building, the greater the annual maintenance costs to keep it clean, repaired and safe. The failure of a single building element can be catastrophic. For example, the silicone mastic used to weatherproof glazing panels was given in its early forms only a 15-year performance guarantee. If mastic fails, it can result in the need to remove and/or repair every single glazing panel in the surface of a building, which in a high-rise building would prove to be a crippling expense. Day to-day maintenance of buildings can be similarly expensive and where building envelopes are problematic to access, they can have enormous annual cleaning costs. One famous tall building in the City of London has allegedly proved impossible to sell because of its astronomical maintenance and running costs, and even relatively lower rise buildings such as the Greater London Authority headquarters can run up annual window-cleaning bills in the region of £ 100 000. Many tower blocks have fallen into a very poor state of repair because their owners cannot afford their upkeep. The historical reality has proved that it is often cheaper to blow up tower blocks than repair them…

Particularly vulnerable to a more extreme climate will be leaky envelopes, typical of concrete panel tower blocks; and glass and steel structures that suffer from very high levels of solar gain are very difficult to shade high up and have traditionally had extreme cold bridging problems through the structure. Tower blocks also typically have to have air conditioning, as they are of sealed envelope construction, a decision that can quadruple energy costs at a stroke, and in turn gives them a disproportionately high carbon emitter status, at a time when carbon taxes for homeowners are being spoken of. So on top of high running costs homeowners would have also to consider that they may have to pay far higher carbon taxes associated with high-rise buildings in the future.

SOLAR, WIND AND LIGHT ACCESS RIGHTS

There are real issues of solar rights with high-rise buildings that have to be addressed and agreed. The higher a building is the greater the shadow it casts on the buildings around it. The shadow cast by a two-storey building is larger than the shadow of a one-storey building of identical floor plan by 2%. A building of 16 storeys casts a shadow 43% larger than a one-storey building, at noon on the winter solstice. A high-rise building will cast a shadow over a huge area of a city, affecting the light and warmth and ability of the shadowed building to generate solar energy. Naturally, if the building is close to the high rise it will be shadowed for most of the year and if it is distant it will be shadowed perhaps for only a period in the day; however, this could be when the solar energy is most needed. Solar rights legislation is being passed in cities around the world and an excellent example is that of the Solar Law of Boulder, Colorado, where legislation has been enforced to ensure that buildings do not steal the sunlight from adjacent properties. There is also a case to be made for wind rights to ensure that new buildings do not cut off the air flow around buildings that may be needed to power ventilation systems or generate electricity.

Two conditions conspire to make daylighting difficult in high-density buildings. One is how wide they are, from one external wall to another. Once the width of a building increases beyond about 12 m it is difficult to daylight it. Not withstanding the depth of a building, the amount of daylight reaching an interior is dependent on how much clear sky is visible from any particular window. The more sky can be seen from a window, the greater the amount of daylight that can enter aroom. In a dense urban setting, it becomes clear that windows close to the ground will not provide significant daylight to interiors in high-rise districts.

Perhaps the worst climatic impacts that are associated with high-rise buildings result from the wind. The increasing height of a building results in two major factors:

● The speed of the wind increases the higher it is off the ground, resulting in higher air pressure experienced on the surface of the building.

● The higher the pressure at the top of the building the greater the difference in pressure between the top and the bottom of the building, increasing the speed of the wind between the apex and the base of the building.

The increasing high-level air pressure causes accelerated air speeds on the surface of the building, significantly increasing air penetration into the building, and out on the leeward side of the building through openings and cracks. This can substantially increase the heating or the cooling load of an exposed high building over the loads of a low- to medium-rise building, often requiring expensive systems of climate control to even maintain a comfortable indoor climate the higher up the building one goes, but perhaps the potentially most severe impacts of wind discomfort occur in the outdoor spaces around high-rise buildings. Many of us will experience such discomfort daily. In the city of London, for example, it is difficult not to notice the significantly increased wind speeds on an ordinary summer’s day in say, Threadneedle Street, adjacent to a high-rise tower. Wind becomes an annoyance at about 5 m/s, by causing clothes to flap and disturbance to the hair. At 10 m/s it becomes definitely disagreeable and dust and litter are picked up and by 20 m/s it is likely to be dangerous. In studies the Building Research Establishment (BRE) found that wind speeds of 5 m/s were exceeded less than 5% of the time in areas of low-rise developments but were exceeded over 20% of the time in areas with high-rise buildings. With the increasingly deep low-pressure systems currently being associated with climate change and their associated increases in wind speeds, the ground-level turbulence and wind speeds in city streets may become increasingly less tolerable for the ordinary citizen in areas adjacent to tower blocks.

Higher wind speeds at street level are also associated with higher windchill factors, making the outdoors even more uncomfortable. Where today problems of outdoor air comfort may result from wind flow down and up from high-rise buildings, they may in future climates become the cause of increasingly dangerous street conditions as wind speeds increase. There are several laboratories in the UK where the wind impacts of new city developments can be tested on models in wind tunnels or through simulation, as for instance at the Universities of Cardiff, Sheffield, Cambridge, UMIST and at the BRE and the National Physical Laboratory. Such wind testing is required by local authorities and by independent bodies, but for current climates only, and not future wind environments.

ABOUT THE AUTHORS

Sue Roaf

Sue Roaf is Professor of Architectural Engineering at Heriot Watt University, Edinburgh, and Visiting Professor at the Open University. With degrees from Manchester University, The Architectural Association and Oxford Polytechnic, she has worked widely on ecobuilding design, carbon accounting, adapting buildings and cities for climate change, traditional technologies, and sustainable and low-carbon buildings. She co-designed and owns the Oxford Ecohouse, the first building in the UK with a photovoltaic roof, and does much to promote resilient low-impact and low-carbon architecture through the research, teaching, publishing and conferences she organizes on Solar Cities, Carbon Counting, Architectural Education, Thermal Comfort and Post Occupancy Evaluation. Her PhD was on the Windcatchers of Yazd and she spent 10 years in Iran and Iraq as an architect, archaeologist, anthropologist, lecturer and landscape architect. She has two sons, Christopher and Richard. She has written and edited 10 books, including Ecohouse :A Design Guide; Closing the Loop: Benchmarks for Sustainable Buildings; and The Ice-Houses ofBritain. She lecturers widely to audiences around the world.

Fergus Nicol

In the 1960s and early 1970s Fergus Nicol researched building physics and human thermal comfort at the Building Research Establishment and the Human Physiology Unit of the Medical Research Council. He also taught in the Schools of Architecture at the University of Science and Technology in Kumasi Ghana and the Architectural Association in London. After a period managing a bookshop he returned to teaching and research in 1992.Fergus is best known for his work in the science of human thermal comfort, where he has developed, with Professor Michael Humphreys, the ‘adaptive’ approach to thermal comfort. He has run a number of projects over the last 15 years funded by the EPSRC and other funding agencies and a major EU project, Smart Controls and Thermal Comfort (SCATS). He is a professor at London Metropolitan University, where he is deputy director of the Low Energy Architecture Research Unit (LEARN). He is an affiliated Professor at Heriot Watt University and Emeritus Professor at Oxford Brookes University. Fergus is a member of UK and European consultative committees on comfort issues. He is helping CIBSE to write the new edition of their Guide A and is an active member of their Overheating Task Force. He was responsible for the international conference Air Conditioning andthe Low-Carbon Cooling Challenge in Windsor, UK, in July 2008, attended by many international experts in thermal comfort and thermal comfort standards. He is convenor of the Network forComfort and Energy Use in Buildings, which boasts nearly 300 members from all over the world and in a wide variety of academic disciplines, consultancies and government bodies.

David Crichton

David is an economist with 30 years’ experience in the insurance industry. He has held senior underwriting and claims management positions in both property and casualty business, and has won a number of insurance industry awards, including the first AIRMIC risk management prize awarded to an insurance practitioner. He is a freelance consultant and researcher on climate change impacts and insurance. He has authored a number of books, reports and papers on insurance and climate change. David has advised governments and insurers in four continents, and has worked for the Association of British Insurers, the CII, the DTI, EU, NATO, NOAA, OECD, various branches of the United Nations, and WWF. He has also been a member of several academic or research boards in the UK. He is a Visiting Professor at the Benfield UCL Hazard Research Centre at University College London This is the leading academic hazard research centre in Europe, specializing in natural disasters and insurance ( http://www.benfieldhrc.org/ ). He is also Visiting Professor at Middlesex University Flood Hazard Research Centre, an Honorary Research Fellow at the University of Dundee, a Fellow of the Chartered Insurance Institute and a Chartered Insurance Practitioner. He is a member of the UK Advisory Committee on Natural Disaster Reduction, part of the United Nations ISDR initiative.

Janet Rudge

Janet Rudge is currently the Energy Officer for Ealing Borough Council, specializing in programmes for the Fuel Poor. She is a registered architect and has worked in both public and private offices. Since 1992 she has researched and taught Environmental and Energy Studies at the University of East London and the Low Energy Architecture Research Unit (LEARN) at London Metropolitan University. She has also worked helping to establish the Network for Comfort and Energy Use in Buildings. Her own research has concentrated on fuel poverty and health, with publications including papers in, for example, the International Journal of Biometeorology, Journal of Public Health and Energy and Buildings. She co-edited, with Fergus Nicol, Cutting the Cost of Cold: Affordable Warmth for Healthier Homes, a multidisciplinary reference source on the health impact of cold homes. Dr Rudge is currently an invited lead expert on cold homes for a World Health Organization European project to assess the burden of disease of inadequate housing.

Sari Kovats

Sari Kovats is a lecturer in Environmental Epidemiology at the London School of Hygiene and Tropical Medicine. Her areas of interest are in health issues related to climate change, and she has published widely on the health impacts of heat waves and associated public health responses, the role of temperature in the transmission of food-borne and water-borne disease, the association between temperature and rainfall and mortality in cities and the health impacts of flooding. She was a Lead Author in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.

Via CityHallWatch and some planning friends.

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