The love affair with tall buildings is undeniable. Architects have, with mixed success, created a number of significant icons.
Questions remain, however, as to whether these buildings actually make cities better places given their impacts on the public realm.
Tall buildings can create a number of common problems:
- Restricted sunlight
- Exacerbated wind conditions
- Lack of activation at ground and lower levels resulting in poor safety and surveillance
- Poor contextual response
These issues, however, can be tackled with good landscape and urban design.
Very simple and effective tools now exist to measure the effects of shadow caused by tall buildings. Using these tools early on in the design process is of great benefit. Towers should be as slender as possible and aligned to allow light into public gathering areas.
Increased shading is still inevitable. Public realm design must respond to this and consider such factors as selecting plants and trees that are appropriate for shaded conditions, creating public space where it can be modeled that sunlight will be captured - especially during peak times such as lunch breaks - and using lighter coloured materials and potentially artificial lighting.
Understanding where areas will be heavily shaded should also determine the location of active ground level uses. Retail outlets typically prefer a sunny outlook, whereas sunny spaces should not be wasted on carpark ramps, service areas and blank walls.
In very hot climates, the reverse situation may be true. Public realm design in some Middle Eastern cities seeks to take advantage of the shading caused by buildings to cool the temperature and provide for more pleasant pedestrian conditions.
Tall buildings are known to exacerbate wind conditions at street level, often causing very unpleasant and potentially dangerous micro-climatic conditions. Early engagement with wind modeling specialists is vital before the building design has gone too far. The modernist box may need to be relaxed in order to create a public realm that people can enjoy without the buffeting effects of the wind.
Strategic planning should look to address wind issues and determine what the collective result of many tall towers in a precinct may be.
Apart from the form, orientation and permeability of the building itself, the public realm can be designed to further ameliorate wind conditions at the street level. Canopies of trees or structures around the base of the building can help disperse winds, pathways can be directed away from specific spots that modeling suggests will be highly wind prone, and shrubs and screens can create protected areas.
The most successful urban public realms and streets are those with mid-rise buildings providing a near continuous building frontage that supports an active street life.
By contrast, tall buildings that sit as freestanding objects in a plaza, such as Le Corbusier, seek to remove themselves from city and street life, creating soulless spaces that no one spends time in. Developing cities in the Middle East and Asia continue along this disastrous path.
The failure of the freestanding object in a space is obvious when one considers that buildings need to have areas for services, carpark access, and other non-active uses. A building in a plaza has nowhere to hide or ability to place these out of view.
A hybrid solution exists whereby the tower is placed on a podium which creates built form at the street level of a human scale and form. The podium, however, must contain active uses and access for the public, not simply a ground level of retail with levels of carparking above. This solution still allows the tower component to be a creative and unique design. If the tower is set back from the podium, the podium can also assist with wind amelioration. Service areas should be located on side or rear lanes.
Neighbourhood character is a dirty term where tall buildings are concerned, especially when proposed in areas previously devoid of such structures.
A structure plan is essential that sets out the scale, form and uses of future development. Allowing open slather could result in 50-storey or greater towers across the entire area creating many of the problems outlined earlier. Design and planning principles must be established such as ensuring towers are placed on or behind human scaled podiums, that building frontages have active edges including doors and windows, that floor levels respond to the public realm, that service areas are placed away from the prominent street frontages and many of the other suggestions already outlined.
The unifying element in all this is the public realm, which fills in all the spaces between and around these tall buildings. Melbourne, for example, is much more defined by its great streets and lanes than it is by its tall buildings. If these streets and lanes are to remain as a defining element of a livable city, care must be taken to ensure the love affair with tall buildings does not destroy them.