Greened wooden pergolas with seating on the Danube Island

In autumn 2020, five wooden pergolas with seating were erected on the Danube Island, overlooking the River Danube. With their greened roofs and graduation walls, the pergolas will provide shade and create a cooling microclimate in hot weather.

Locations:

• Three pergolas are situated on the Danube side of the island near Kaisermühlen Bridge.
• Two further pergolas are situated on the edge of the grassy area next to the splash park.

Both locations were chosen because their proximity to Reichsbrücke bridge and the splash park makes them very heavily frequented.

Graduation walls create a cooling effect

Each pergola is backed by two graduation walls to create a cooling effect on hot summer days. These consist of oblong steel frames containing a lattice stuffed with bundles of brushwood on both sides. The bundles are made of blackthorn twigs, the wood best suited for this purpose.

Water is made to trickle down over the bundles of blackthorn twigs, forming small droplets that quickly evaporate and thus draw heat out of the surrounding air. The excess water is drained away. The graduation walls are digitally controlled, with the water supply switching off automatically at night and when it is raining.

Green roofs replace asphalt

Three of the five trapezium-shaped wooden pergolas have been erected next to a circular grassy area close to Kaisermühlen Bridge where the City of Vienna planted 25 wild fruit trees in spring 2020. The grassy area is surrounded by asphalt, which was removed on the riverward side to make room for the pergolas.

This has created approximately 210 square metres of new green space. Climbing plants have been planted alongside the corner posts of all the pergolas, and will soon grow to cover the entire roof and sides of each structure.