29 January 2018

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On Wednesday 24 January, Mayor Pauline Krikke opened the World Trade Center The Hague’s sustainable polder roof garden with water catchment facility. It is the first flat roof in The Hague to be turned into a polder roof garden.

In December 2016, WTC The Hague, owned by Bouwinvest Dutch Institutional Office Fund, was the first multi-tenant building in the Netherlands to be awarded the prestigious BREEAM-NL In-Use Excellent sustainability award. The conversion of the parking garage’s flat roof into a roof garden is part of WTC The Hague’s unique journey to even greater sustainability. The Mayor calls the roof garden and water catchment facility a gain for the city, an inspiration for other companies and the perfect example of sustainability. For further information, please see www.wtcthehague.com.




Unique polder roof garden
WTC The Hague built the ‘polderdaktuin’ as another step towards becoming even more sustainable and to meet the wishes of the tenants and residents of the building for an outdoor space. Marinka de Kok and Manja Meuleman, landscape architects at Buro Kokmeuleman, took on the challenge of turning the garage roof into a sustainable spot for people, fauna and flora. Nestled between offices, the roof gets plenty of rain and wind, little sunlight, and there is little evaporation. These conditions make it perfect for planting indigenous plants that will grow and flourish. Marinka de Kok explains that ‘we created an isolated mini environment in the enclosed space. The captured rainwater creates a permanent pool of water. The plants retain this water and will create natural evaporation. As the plants are indigenous, they will encourage indigenous insects, birds and water creatures to make their homes here.’

Water regulation
The polder roof garden will be used as a water storage facility. This will make the surrounding area more sustainable and will improve the inner-city water management. The rainwater gutters of the surrounding roofs will be disconnected and the rainwater will be collected in a basin. The water will be retained, used naturally and, if necessary, for example after a heavy rain shower, will be drained into the sewage system. Dakdokters’ innovative Aqua Flow System will detect rain showers through the Buienradar website and will reduce the water level so that the rainwater can be collected in the garden. After storage and natural water usage, any excess water can be drained through a dyke system into the sewage system. In total, 420m² of the 700 m2 garden will comprise water.

Sustainable course
In December 2016, the WTC The Hague was the first multi-tenant building in the Netherlands to be awarded the prestigious BREEAM-NL In-Use Excellent sustainability certificate. According to Managing Director Eveline Steenbergen, ‘WTC The Hague is very large, and the building thus uses much of the sewage capacity of the area. By disconnecting the rainwater drain and regulating it on our own premises, we can reduce the pressure on other companies and residences in the area.’ The conversion of the flat roof into a roof garden and water catchment facility is evidence of Bouwinvest’s and WTC The Hague’s commitment to becoming even more sustainable.

WTC The Hague’s commitment to sustainability is also evident in several other measures such as using LED lights and placing nesting boxes to help increase the population of sparrows.