Copenhagen: Garden up high

The vertical garden on the gable end of Dannebrogsgade no. 21 facing Otto Krabbes square is CityGardenNetwork's (ByHaveNetværkets) perception of up-to-date local use of rainwater. The project took seven years to complete and now stands as an effective and sustainable urban solution created in collaboration with the Municipality of Copenhagen.

Recycled house bricks have been used to build a staggered structure, interrupted by blue areas of lime mortar and marble plastering. Water flows down the blue areas several times a day. Water is pumped up to the top of the blue areas from a 12 m³ tank located below the gable. Just how much water flows depends on weather conditions and on how much of it has collected in the tank. Water flows from the surfaces into a pond which functions as a simple water purification plant. Reeds and gravel in the reservoir remove particles from the water, and green plants absorb nutrients in the rainwater.

Water overflowing from the pond runs back into an underground water tank, where an exfiltration pipe consisting of 12 coffers allows the water to seep down into the groundwater. Circulation of water on the gable and in the pond also means that much of the water evaporates before it reaches the exfiltration pipe. The combination of evaporation and seepage through the exfiltration pipe means that no rainwater from the building flows into the Copenhagen sewers or the local purification plant. This makes the project an extremely good example of efficient use of rainwater.

Localised utilisation of rainwater is a necessary initiative in Denmark, where rain water is traditionally led straight into the sewage system. Expected changes in the climate mean that it is doubtful that the sewers will be able to drain off the quantities of rainwater expected to fall in the future. Initiatives such as the vertical rainwater garden paved the way for a new approach to use and handle water, and adapting existing urban areas and housing stock to the new weather conditions.

Apart from the vertical garden's efficient drainage of rainwater, the garden also enhances the cityscape. Within the garden's brickwork cavities have been made to accommodate the city's birds and nesting boxes have been built into the brickwork at the top of the gable for the common swift. Climbing plants will grow up the gable and rare wall plants have been planted in the cavities. The green sections of the vertical garden will develop over time as the brickwork is taken over by flora and fauna as a living contrast to the city's more traditional, homogenous facades. The gable end in Vesterbro with its various functions is a fine example of multifunctional vertical architecture.