Green (ventilation) grids

Delft 2009 © Andre Vaxelaire

Green and half-open linear structures in an urban area enhance urban ventilation and contribute to the exchange of air between city and surrounding and between green and residential areas. Half-open areas with stands of trees are most effective for an optimal airflow.

A grid of parks and small areas of vegetation that are connected to one another not only affects the microclimate and the residential buildings adjacent to the green areas, but in periods of heat stress will offer more pleasant places for city dwellers to be and a pleasant network for slow-moving traffic.

Green grids in a town or city that are connected with the cooler countryside make it possible for air to move. The vegetation in these green grids should not be planted too close together, to make it possible for the wind to pass through them. In towns and cities situated in valleys, it is important to create corridors to allow cool air to flow in from green hills at night. Ministerium für Klimaschutz NRW, 2011

The concept of a lobe city was developed early in the 20th century. In the 1990s, Tjallingii studied the idea in relation to sustainability. His research showed that the lobe plan is suitable as the basis for sustainable urban development and for blue-green urban planning.

principle drawing of a green ventilation network - Source: atelier GROENBLAUW, based on Klimawandel, 2011
By placing buildings and green areas in the correct proportion and direction, the green ventilation flow can reach the inner parts of the city. - Source: atelier GROENBLAUW, based on Klimawandel, 2011

The green-blue lobes have a favourable impact on the urban climate: in the summer they hold less heat and so offer cooler areas. The difference in pressure between the hot and cool areas also causes airflow and ventilation. Hermy, 2005

Lobe cities offer the possibility of combining the benefits of compactness with those of more open and green development. The growth potential of these cities is limited. For large urban conglomerates, green grids are a more viable solution. Ministerium für Klimaschutz NRW, 2011

Lobe city - Source: atelier GROENBLAUW, based on Klimawandel, 2011