Each rooftop garden is a little bit mysterious: roofs are usually inaccessible and need to be conquered. You need to climb a lot of stairs or use the lift, and then open the hatch. Often we do not know what to expect on top and what we will see from above. And let’s think about it for a moment: a garden several or several hundred meters above the ground? What can grow on a building? Does it look like a winter garden, a park, a vegetable patch or a meadow? Why would you even want to put this green hat on a building? Our curiosity keeps increasing as we approach the top. Because to conquer a roof is to discover the unknown. We invite you to explore the secrets of our green garden above the Copernicus Science Centre.
Growing plants on rooftops is not an invention of modern times. We all know the Hanging Gardens of Babylon with aqueducts and fountains. In the nineteenth-century Berlin, sod roofs were considered to be protection against fire. In Scandinavia, in turn, the grassy roof sheathing protects against harsh climate. In the twenties of the twentieth century, the idea of recreational green space on rooftops was promoted by the French architect Le Corbusier. Today, roofs covered with vegetation are created in many parts of the world. Barcelona Green Infrastructure and Biodiversity Plan 2020 assumes covering roof, walls and terraces of the metropolis with greenery. Almost every new development or major modernisation of a building in the city includes a design of a garden on the rooftop, often including the systems for harvesting natural energy sources. Under the Common Roofs programme, the municipal budget subsidises neighbourhood initiatives to readapt the top levels of houses and blocks of flats.
Gardens on buildings in urban areas are patches of greenery soothing the tired eyes and calming the nerves. A short walk in such a garden or even just looking at the vegetation from behind the windows of a nearby office increase concentration and self-control and inhibit aggression. Green roofs are often the perfect place for walks, recreation and rest. They can also attract birds and insects. This is the role also played by the roof of the Copernicus Science Centre: the building was created within the Natura 2000 area of special bird protection: Mid Vistula Valley. For some time, there was even a duck in the garden, which made itself at home there and created a nest.
Apart from being a habitat for animals, green roofs perform other ecological and economical functions. They absorb up to two thirds of precipitation, which reduces the amount of water drained to urban collectors. The biologically active roof of the building provides thermal insulation: in summer, when the normal roof heats up to 80°C, the green surface may be at ambient temperature, whereas in winter, it provides additional thermal insulation. Plants retain and process dusts and harmful substances, as well as reduce noise by approx. 8 dB. Green roofs improve the microclimate: moisturise the air and hamper its movements. They help to reduce smog and combat the urban heat island effect characteristic of concreted built-up areas. The air temperature in those heat islands can be even 10°C higher than in suburban or agricultural areas.
The role of green roofs is especially appreciated in Singapore: up to 80% of the inhabitants of this modern garden city were in favour of formation of biologically active areas on buildings. Singaporeans emphasise the recreational role of such space. It was important for them that they could relax in beautiful natural surroundings. It is probably also the reason behind the idea to have walls covered with plants, creating vertical gardens. The largest garden of this type in the world is located exactly in Singapore, on the facade of the 24-storey apartment building called Tree House. It has the area of 7,5 km². It is assumed that each year it will bring 500 thousand dollars in savings for the cost of energy and water.
Despite the proximity of the Vistula River, the climatic conditions on the roof of the Copernicus Science Centre are not good for growing plants typical of the riverside. The garden is an artificially created habitat, it is exposed to intense sunlight and there is no windshield. Many of the plants grown there are xeromorphic species, genetically adapted to life in adverse conditions of the so-called water stress. Their construction helps them to minimise transpiration. They have leaves covered with hairs (e.g. common yucca) or wax (cloves, stonecrops, blue fescue). Some of them have developed extensive root system (mountain pine). Others, succulents, such as the stonecrops present in our garden (e.g. goldmoss and showy stonecrops), gather water supplies during times of their accessibility: they are fleshy and juicy.
Many of these plants–grasses, shrubs and perennials–cover the so-called extensive roofs that do not require complex care, but are not always designed to hold a garden. This is why they are not prepared for heavy loads and cannot act as recreational areas. However, this is not the case of the roof of the Copernicus Science Centre. Although we will find many small plants with modest growing requirements there, the roof was designed to hold the garden and all its visitors.
Urban greenery is much more than the landscape. It fulfils the metabolic and recreational functions. It is a place to rest and it can be a space for many interesting activities.
We invite you to explore the green hat of the Copernicus Science Centre.
Publication date: 27 August 2014