Sustainability at the Urban Scale

For the Irish Architect
Brian O Brien- Jan-01

Designing buildings more sustainably is critical to improving the resource and energy performance of society's activities. Buildings, however sustainable, though are limited in their ability to influence the patterns of energy and resource usage, waste minimisation and material choices outside their own walls where transport, urban design and land use become more critical. The expansion in the role of many architects to carry out urban designs and an increased awareness of the importance of 'design' over 'density' in recent planning reports points the way to opportunities for architects to improve our cities through urban design that is more sustainable.

But what is sustainable urban design ? Urban design might be said to be the 'composition' of the city's elements (buildings, open spaces, activities) so that they add up to a higher quality experience than the sum of the elements. Might sustainable urban design be a composition where the urban experience is more self-supporting, efficient and resilient. Sustainable city design increases complexity in how the city performs. It provides many different ways to fulfil each of the city's physical functions, (movement, shelter, energy, manufacture, waste management) in much the same way as the natural world operates; the designing out of inefficiencies and the designing in of beneficial relationships.

The question of energy is always the first thing to come to mind when sustainability is mentioned. The most efficient way to look at urban energy planning in Ireland is to consider buildings in combination. Group heating systems purposely designed to suit the cluster, or community of building scales, powered by renewable resources (wind, solar, biomass or heat pumps) can offer remarkable efficiency. Such technologies have come a long way since the days of Ballymun's crude system were installed in the sixties and current true potential allows for easy changes of source fuel without disruption to the consumer buildings. A good example is the new system that connects Dublin's Civic Offices with a number of nearby hotels and commercial areas. Another aspect of this is 'combination' thinking may lead us to place building with different energy appetites adjacent to each other matching a daily or seasonal excess of heat or energy in one with a deficit in another.

In the future its clear that we will begin to see the structures of the city itself emerge as energy creators, examples already exist; photo-voltaics integrated into road overpasses in Switzerland and Copenhagen's wind turbines standing gracefully at home in the ports skyline of cranes and gantries. Again in the future we may see individual buildings, each producing energy in different ways, networked together to allow energy sharing as availability varies with weather and consumption, using the flows and returns possible in a complex network and avoiding the need for expensive energy storage systems.

Solar design is the most effective sustainable design strategy applicable to the Irish climate. At the urban scale this requires designers to balance the need for spatial enclosure, hierarchy and definition in laying out buildings and public ways with the need to maximise the surface areas of buildings exposed to the Sun's energy. We may need to invent a new palette of urban forms to satisfy this requirement, the circus instead of the square, the crescent instead of the street, a typology of asymmetric street walls whose heights vary to allow maximum solar radiation on building facades.

While energy may be the connective tissue in cities, transport is the lifeblood of the system. The backbone of any sustainable urban design strategy is land use and public transportation. Achieving densities that can support public transport, by zoning, area planning, or fiscal instruments is essential. Many cities are moving to low or no emission transport systems while some actually use their vehicles to generate energy. Investment in public transport is always felt as being costly but the quantum benefits of reduced maintenance, increased accessibility and higher air quality, not to mention the reduced stress among the motoring population far outweigh the costs. Putting the facilities in place in advance is essential. The new urban quarter at Pelletstown is one of the most exciting examples of this type of urban design in the country.

The materials used in the public realm also affect the daylight potential and comfortableness of nearby buildings. Badly designed outdoor lighting whether in the public or private realm results in light pollution (defined as wasted energy) which not only reduces the natural experience of dark sky for city dwellers, but also interferes with wildlife and rural amenity for many many miles around. The numbers of stars visible over a city is now one of the prime indicators of efficient lighting design and control internationally.

The air that moves through a city is another vital ingredient of well being. Meteorologists talk about the 'airshed', likening it to a watershed, which reminds us that air always comes from somewhere and, as with water, always goes somewhere after we have used it. Cities can actually clean their air by using vegetation and water in their composition to increase air quality and to counteract the heat island affect where urban areas are actually a few degrees higher in temperature (and have lower air quality) than the surrounding region.

Water is perhaps the most important resource that a city consumes and urban design can create a much more sustainable usage pattern if considered in advance. Water can be supplied nearer to source by implementing rainwater harvesting systems for groups of buildings, especially for non drinking water. At present all mains water is treated (with massive costs and inefficiencies) to potable standard though only 12% is consumed. A new urban vision seeing water as a valuable resource might herald the provision of multiple supply lines; pure water supply, white water(ie clean but not drinkable) and grey water(ie dirty, but full of nutrients, heat and still non toxic) and of course wastewater.

Again we need to see our city as an integral part of the natural watershed that surrounds it. The city of Dublin has more than 30 rivers flowing through or under it, yet few if any residents experience the benefit of them except in the case of the Liffey, Dodder and Tolka. Initiatives to 'daylight' these buried rivers is on the increase in US cities and brings major improvements in eco-literacy enjoyment and bio-diversity.Public spaces, parking areas and roads should be designed to be much more porous allowing rainwater to reach and replenish the water table underfoot, protecting foundations, vegetation and wildlife and relieving the stress on surface water drainage systems.

Water once used in the city may also be treated using more natural systems. Living machines, or in less dense areas, constructed wetlands (reed beds) can be designed into complexes of buildings and open spaces such as parks.

Most Irish cities do not allow for food and plant cultivation. Yet across the world the benefits of community gardens, urban farms and city forests are being seen. Wildlife too is an aspect that strikes fear into the heart of urban designers. A well designed matrix of urban wildlife corridors, patches and refuges encourages the emergence of diverse wildlife communities, reducing the niches available for many of our most loathed urban pests; rats and pigeons. The new wildlife bridge in Mile End, London (by Piers Gough ?) is wide and deep enough to support trees, vegetation belts and bikeways and shows the design opportunities of accepting wildlife in the city.

Finally sustainability calls for the inclusion of industry and employment within the city while designing out waste, traffic and noise. Industrial Ecology is an innovative approach, at an urban scale, to tune the outputs of one industry to the required raw materials of another, located nearby in a kind of 'synergistic' composition. The best example is in Denmark where heavy industries and energy generation are plumbed to light and small industry. Outputs and efficiencies are higher while traffic and waste is minimised.

So what are the principal challenges. Clearly some new legal rights will have to be established. Buildings and city quarters designed to power themselves on ambient (solar, wind or ground source) energy must be protected from changes in the availability of that source caused by adjacent development. Rights of light must be broadened to include rights of air, water table, solar access, vegetation and shade. Public infrastructure supplies may have to change. In the same way that fibre-optic cable is being installed as an upgrade in the telecommunications networks, supply webs for renewable energy; heat, clean as well as potable water, and disposal networks may be installed across new urban developments.

In some ways its harder to make an impact on the environment when dealing with large scale networks of buildings (whether city quarter, town, or housing estate). There are more players and decision makers involved, more people to be consulted, competing financial and aesthetic interests and often long periods between decision and action. In other ways the potential for creating benefit is far greater, often a commission to carry out urban design signifies an immediate appetite for change, a will to implement and the availability of large scale resources. Accepting these potential opportunities and broadening our view of urban design to embrace sustainability will strengthen both our cities and the environment. In addition it can only reflect well on our profession and that's good news for us as well.

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