'Integrated performance management'

The world of roof gardens and vegetation roofs has increasingly become multidisciplinary. "More and more often we are integrally involved in sustainable building designs," says commercial director Aart Veerman of Van der Tol - nationwide specialist in design, engineering and installation of roof greenery. "Sometimes even literally with constructive contributions to the building, such as at Depot Boijmans van Beuningen."

The roof gardens and vegetation roofs segment has become a structural part of sustainable building designs since the late 20th century. Veerman: "In recent decades we have both tried to meet market demand and pioneered technical solutions. Especially customization with regard to slope and rainwater runoff has become more important, and recently you increasingly see a combination of water storage, heat reduction, utilitarian greenery and biodiversity." In sustainable multiple use of space, roof greenery can play a major role. "We represent a product that is ideally suited for innovation in chain cooperation. Eco-engineering is what we call it."

Meteo Active water storage

After all, a green roof does not stop at the roofing. Within knowledge platform Living on Roofs, gardeners, roofers, installers, suppliers and manufacturers form collaborative teams, which can provide guidance from advice to maintenance and management. "The key is to work integrally with other stakeholders in construction to achieve intelligent buildings that contribute to the built environment," continues Veerman. "For example, for the vegetation roof of De Doelen in Rotterdam, we are working with software, Meteo Active, in which, based on actual rainfall data, water is either delayed or accelerated to the buffer system, and for the roof forest of Depot Boijmans van Beuningen, a loose decking floor was developed and constructively anchored to the eaves on steel, in order to actually create a user roof."

Capturing peaks

Integral solutions combined with green roofs can contribute substantially to the increasing peak load from downpours. An interesting discussion, argues Veerman. "Should you necessarily solve the load on the sewer system from short, heavy downpours by expanding the existing system? We don't think so. Precisely the peaks can be absorbed by innovative water storage systems at the plot level." From that starting point, sewer investments can be approached differently in the future. "That means that within the depreciation period of the existing system you can come up with new solutions together, such as completely disconnecting buildings from the sewer system." 

Proven performance

These then provide their own drainage, such as the green residential building Vertical in Amsterdam, where rainwater is completely collected in the various layers of the roof garden structure. There is still room for improvement, Veerman believes. "We approach our profession from knowledge and expertise, including bringing research results and big data to stakeholders, such as municipalities. We focus on proven performance, not just promises for the future, and have the people in-house to supervise design, engineering and execution. All our work at Van der Tol is based on our vision of the importance of green for the city. "