Case studies - Living Roofs in Integrated Urban Water Systems - page 156

quality of stormwater runoff from the living roofs had to be upgraded on-site to
potable-grade water. This ensured that the project's water features and irrigation
would be independent of the municipal water supply.
2 KEy CommUNITy BENEFITS
One of most notable attributes of the Potsdamer Platz is that it successfully used
existing planning policies to encourage innovative holistic design and strong
public and private partnerships that seek to achieve mutual goals. The large scale
of the project was taken seriously, and design solutions were targeted at address-
ing design concerns appropriate for the scale of the development. In the case of
Potsdamer Platz, the 19 living roofs were created to provide mitigation of envi-
ronmental impacts. In addition to mitigating the prospective disruption of the
water cycle created by the impervious city blocks, the living roofs also provided
signiicant microclimate cooling, reducing air-conditioning use during the summer
months.
A community beneit also integral to the design was consideration of the
planning permissions policy. Because housing was proposed on the site, play
space for children had to be provided in the vicinity of those proposed housing
areas. In case of the Potsdamer Platz, no at-grade areas were available. There-
fore, play areas were integrated into courtyards above the parking garages of the
buildings. These intensive living roof areas were planted with shrubs and trees,
which have a high water demand and had to be supplied with irrigation. Water
harvested from the living roofs was intended to supply irrigation for the purpose
of creating a viable children's play space with lush planting.
3 RAINWATER CoLLECTIoN
Landscape architects Krueger and moehrle designed both the intensive and
extensive roofs of the project. The extensive inverted roof assembly varies
between 15 and 25 cm in depth and is comprised of materials by different manu-
facturers including a synthetic drainage mat and an extra layer of a geo-
composite drainage mat. This extra layer was used to provide an extra air buffer
for the inverted roof assembly to encourage evaporation of water underneath
the roof's loating insulation.
Three mainly inert growing media mixes were tested before construction at
the Technical University of Berlin to monitor nutrient seepage, which could
increase algae growth in the artiicial lake at grade of the site (Köhler and
Schmidt 2003). Due to the appropriate selection of the growing medium, nutri-
ent seepage was reduced and the problems associated with algae growth were
minimized.
The project began construction in the early 1990s, when stormwater manage-
ment research on living roof's was still in its infancy. The cisterns were sized for
the roof's stormwater runoff without living roofs. In the process, they were over-
sized for the amount of runoff generated from the roofs but undersized for irri-
gation demand. Since completion of the project, the cisterns have been illed