Archipelago Roof Gardens in the World’s most Livable City

An archipelago is a small, flat and often rugged rock island typically found along the Baltic coast. And, the 86,000 ft² roof garden of the Tivoli Hotels & Congress Center in Copenhagen actually does resemble these rocky reefs. This is due to the fact that the many plant beds with their irregular contours are located like islands in the middle of the extensive pathways. A unique lighting concept means that the elaborate roof garden is an attraction for hotel and congress guests and tourists to Copenhagen even at night-time. Thanks to ZinCo green roof technology another part of this pedestrian pathway has been completed. The pathway can now be used without interruption along a stretch of approx. 1,440 ft.

The Danish capital of Copenhagen is one of the most important cities in Northern Europe. It is a popular tourist destination and sea port and has been honored on a number of occasions as the “Most livable city in the world”. The district of Vesterbro – which only a few years ago was known mainly for being a transit zone for traffic into the inner city – is experiencing rapid development which is breathing new life into the area. Green areas are contributing considerably to this, one example being the green pedestrian pathway at an elevation of approx. 33 ft which starts at Bernstorffgade and continues between buildings, running parallel to the Copenhagen canal: from the Danish “Rigsarkivet” (National Archives) building, which has a roof area of about 80,700 ft² and is greened with ZinCo system technology, over a landscape bridge and on to the building complex housing the Tivoli Hotels & Congress Center. This development will be further expanded towards the southwest with green areas, producing a new and attractive city center locality – not far from the shopping area, the port and the famous, eponymous Tivoli Gardens that opened in 1843.

Architecture creates elevations

The entire complex was designed for the Arp-Hansen Hotel Group by the renowned architectural practice Kim Utzon. It consists of the Congress Center with 55 conference rooms for up to 4,000 guests and now has three hotels in differing price categories. The large congress hall is situated on the green roof between the hotels and, in terms of design and contour, it too would remind you of a rock formation. Large-scale glazed facades and partially-glazed folding walls open up this room to the outside world. Also facing in this direction are the restaurants that are on the same level in the surrounding hotels. They provide an uninterrupted view of the varied design of the green roof that reflects the natural features of Denmark: the archipelagos.

The technology beneath the “green”

A professionally-installed and root-resistant waterproofing provided the basis for the 0°-roof area to be greened. Then, the first layer of the ZinCo green roof system “Roof Garden”, the protection mat ISM 50, was installed. Next was the drainage and water-retention element Floradrain® FD 60, infilled with the purely mineral-based clay tile growing media “Zincoblend M”. This growing media allows for a high level of water retention in addition to excess water carry-off through the underlying channel system of the drainage elements. The system filter SF was installed next and was followed by layers of a mineral sub-substrate and the growing media “Zincoblend I” as top soil and at a total depth of between 16 and 30 in. The growing media depths vary because additional growing media is needed to provide sufficient space for the root balls in those areas where trees are to be planted. The structural design of the new building took into account the greater loads of this intensive green roof with small trees. In addition, native plants are used in the plant beds, mainly conifers, grasses and ground cover along with both perennial shrubs such as lavender and seasonal plants such as black and white tulips.

Patterns and light effects on the roof

A base course of foam glass gravel, approx. 30–44 in in depth, was used as a foundation for the pathways that account for about 60 % of the roof area. The pavement material used is China granite, elaborately laid in a Harlequin pattern. This special pattern allows for the creation of entirely irregular contours for the many plant beds that lie there like archipelagos in the sea.

Protection from floods

Due to extreme weather conditions and ongoing global warming, the people in Copenhagen have frequently to deal with floods. A green roof is one way of counteracting flooding and providing relief for the sewage system. Green roofs can retain 50–90 % of precipitation, depending on the type of roof. The greater part of this water is retained in the system build-up and evaporates over time and excess water runs off after a considerable delay. The intensive green roof at the Tivoli Congress Center with its growing media depths of up to 30 in retains approx. 80–90 % of precipitation. The extensive green roof of the adjacent Rigsarkivet building with growing media depths of at least 3 in retains about 50 %. Green roofs are strongly promoted in Copenhagen due to the wide variety of environmental benefits they offer.

Living urban space

With the roof gardens of the Tivoli Congress Center and the Rigsarkivet building, a cohesive chain of public spaces has been created for pedestrians and cyclists in Copenhagen, similar to the High Line in New York. Both in Copenhagen and New York the elevated park is enormously attractive and is stirring long-abandoned city districts to a totally new life.