HEAD 2 HEAD: YES: James Pikesays suitably sited high-rise towers can help meet the challenge of containing a rapidly growing city.
There is no doubt that if we carry on with our current sprawling pattern of development in Dublin, the quality of life for most citizens will deteriorate further, as commuting times increase. This will also reduce the city's attraction as a location for key players in business and education worldwide.
Current estimates show that the population of the Dublin region can be expected to grow by at least 700,000 over the next 25 years and that at least 500,000 of that growth needs to be within the Dublin conurbation. This would still mean huge growth for the satellite towns within the region.
Much of this growth will have to be provided in the townships on the urban edge, such as Adamstown, the Leopardstown/Cherrywood corridor and the north fringe. These are already being developed at much higher densities than existing suburbia and are well served by public transport.
The new Adamstown, which took at least 25 years to plan and build, will provide for only 250,000 people, so the challenge remains to intensify and grow the city centre and the existing suburbs.
Of course, increased density does not mean high-rise, but high-rise is hard to define and relative to the immediate built environment. Six stories in two-storey suburbia could be considered high-rise, whereas 20 stories in Manhattan would be considered low- to mid-rise.
Densities of up to 50 dwellings per acre can be achieved by three- to four-storey developments, but this is difficult in many suburban or even inner-urban sites that are surrounded by existing one- and two-storey housing and there are very few sites in central Dublin or the suburbs large enough to allow development densities to be maximised.
Densities that could be achieved in our inner-urban streets are going to be further reduced by the new standards for apartments introduced last week by Dublin City Council. These standards have a very worthy purpose of making apartments more family-friendly, but they will mean considerably fewer apartments on a length of street frontage. Thus there is more pressure to increase building height in order to achieve good urban densities.
Most residential development in central Dublin to date has been low- to medium-rise, in line with existing building heights. Slightly greater heights have been achieved in major redevelopments such as Dublin Docklands or Smithfield, which address larger public spaces or water frontage. However, considerable criticism has been levelled at the Docklands for creating too even and uneventful a profile.
This was only broken to date by the Millennium Tower at Charlotte Quay with a modest 18 stories, of similar height to the adjacent Boland's Mills, but it is now joined by the new, slender tower on the other side of the harbour.
Further landmark buildings at about the height of the Spire (120m) are emerging at key gateways at the Point Depot and the U2 tower on the opposite bank of the Liffey and also at Heuston Gate. I would consider that such landmark buildings at key points in our sprawling city are vital, as long as they do not compromise existing housing or historic buildings.
Are such high-rise buildings sustainable? They can be designed to zero carbon standard and they maximise development at key transport hubs. Building costs are higher, but they fetch more money.
I would therefore defend the siting of a tower at the Jury's site in Ballsbridge, although I feel it needs refinement in slenderness and a little reduction in height. It is sited at a key point of one of Dublin's major inner-urban townships. It creates a focal point at the end of Dublin's grandest 19th century terrace in Pembroke Road and does not impact on views from the surrounding grand, tree-lined roads. It will also complement the curvaceous but considerable bulk of the new Lansdowne Road stadium. Many of the lower buildings are going to create no more impact than the existing hotels and office buildings and promise to be much more refined, but some will need to be reconsidered.
Where else in the city is high-rise justified? At key locations on the urban edge or regenerated industrial estates such as Sandyford, or as focal points of major townships such as Ballsbridge or Heuston Gate, if suitable sites can be found. But I consider our greatest opportunity presents itself on the Poolbeg Peninsula and more particularly the existing Dublin Docks, which must inevitably be moved out in large part to Bremore, presenting a wonderful opportunity to create a major new city quarter, with up to 80,000 inhabitants at the heart of a magnificent bay, far from immediate impact on existing communities, and at present marked only by power station chimneys.
James Pike is a director and founder of O'Mahony Pike Architects and author of Living Over the Shop, which was recently published by Comhar, the national forum for sustainable development.
NO: Sue Roafsays that climate change and peak oil mean that the age of the skyscraper has passed.
The age of skyscrapers is at an end. It must now be considered an experimental building typology that has failed.
Let's pretend you are choosing a new flat in a city location. What is the maximum number of storeys that that building should be if you want to remain comfortable and safe in that building over time? The world is getting warmer and the fourth report of the Intergovernmental Panel on Climate Change, published last April, is much more alarming that the first three.
On top of that, oil will be really expensive by 2020, because we have now passed the peak of oil production for global supplies.
The last place in the world that you want to be when the lights start going out in an extreme weather event like a violent storm or a heatwave is 20 stories up in a glass tower!
I give a wide range of good reasons why we should never build tall buildings again in the book, Adapting Buildings and Cities for Climate Change: A 21st Century Survival Guide. The height of a building affects its internal climate. It has proven nigh on impossible 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.
A building develops its own internal micro-climate, and heat from the lower floors will rise by natural buoyancy, making the higher floors hotter. The higher the building, the greater this problem of thermal stratification, and the more energy has to be thrown at cooling the upper floors. Tall buildings, by their very nature of being tall, can use twice as much energy as equivalent low buildings.
The higher the building, the more it costs to run, because of the increased need to raise people, 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 it out, and the more the wind pressure on the envelope sucks heat from the structure.
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.
With increasingly poor standards of environmental design, including widespread excessive use of glass and rapidly increasing levels of equipment use, in particular of computers, air conditioning becomes more and more essential. Air conditioning can quadruple energy costs at a stroke, giving 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 also have to consider that they may have to pay far higher carbon taxes associated with high-rise buildings in the future.
The bottom line is that the cost of conventional energy will soar over time and glass towers are the most expensive buildings on earth to run, with their lifts and the water pumping and the fact that they need much more heating and cooling, being stuck up there, exposed to the worst of the sun and the wind and the cold.
Who knows what global economies will do in a fossil fuel-challenged future - but you certainly cannot run a glass tower on renewable energy. For example, the geometric properties of towers make it difficult to utilise solar hot-water systems for occupants because of the low ratio of the external building surface area to the number of occupants.
The lights in cities around the world are going off more commonly every year and you should choose a flat to which you can easily carry a bucket of water to and walk down from comfortably to do your shopping when the power in your neighbourhood does fail. And don't forget that the home should remain tolerably comfortable, even in extreme weather when those lights do go out.
It is difficult to understand exactly how different the 21st century will be from the last 100 years, but the smart money won't go aloft in the future - not least because smart money does not want to live in a "target building" since 9/11.
If you were thinking of buying the "full-view" penthouse on the 40th storey of a new tower, with fixed windows and central air conditioning, do your children and yourself a favour.
Think again, because it is likely to be a bad investment in the short, medium and long term too. Play safe, because you will need to in a rapidly changing 21st century.
Sue Roaf is visiting professor at Arizona State University and at the Open University. She is an author of numerous books and academic papers, an Oxford city councillor and works with the Green Consultancy and the Carbon Trust.
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