Green roofs are the future of modern and sustainable cities

Doctor, what are green roofs and how long have they been around, as they are not a modern idea.

A green roof is defined as any open surface covered with plants, separated from the natural ground by an engineering structure. Plant-covered roofs were created unconsciously, as moss or turf seals of huts, as early as the Neolithic period. In contrast, the beginnings of the conscious establishment of green roofs by humans date to around 4,000 BC. This involved covering the still primitive buildings with turf from nearby meadows and concerned rather colder regions of the world. At the same time, the first ornamental roofs began to appear in the warmer region of Mesopotamia. They covered huge, several-storey religious buildings called ziggurats. The famous 'Hanging Gardens of Semiramis' date from a much later period, around 500 BC, but they have been named one of the seven wonders of the world.

Green roofs are said to be the future of modern and sustainable cities. What function do they have in urban spaces?

First and foremost, green roofs are additional green areas in places without natural ground. They are therefore a solution to the green deficit in the sealed, concreted structure of the city. Their functions relate to all the benefits associated with the presence of plants: such as oxygen production, reduction of carbon dioxide and other pollutants, including particulate matter, improvement of the microclimate, enhancement of biodiversity, reduction of the urban heat island effect, as well as rainwater retention, noise attenuation or thermal insulation.

So the advantages of this ecological and practical urban solution are numerous, and what benefits does a green roof bring to a building owner?

Here, too, the benefits are numerous: from additional space with natural vegetation to actual financial savings. Green roofs prevent heat loss during the cold winter months, and at the same time prevent excessive heating of the building interior during the summer heat. It is therefore possible to save both on heating the building and on air conditioning. In addition, combining PV panels with greenery, i.e. using biosolar roofs, increases the lifetime and efficiency of PV panels, depending on weather and location, by up to 18 per cent on an annual basis.

In Europe, 'living roofs' are extremely popular. Many of them can be seen in the Nordic countries, in Switzerland and also in the Netherlands, for example in Amsterdam. What stage are we at in this subject in Poland?

Poland is also seeing the development of this industry, we may not have as many square metres of green roof space as Western European countries, but we are slowly moving in this direction. It is a positive phenomenon that green roofs are more and more often not treated only as an obligatory element in the case of new development due to the need to ensure nature compensation. Biodiverse or biosolar roofs are appearing, but also as a kind of publicly accessible park.

And what is the situation in Wrocław? Do you know of any examples of good practice in this area? Does the city support such investments?

Of course, such examples include the "Wroclavia" shopping centre with its green roof accessible to everyone or the "Hydropolis", which is completely covered in greenery. Many service and residential buildings are covered with plants, we just often don't realise it. Even in our neighbourhood: part of the roof of the Pasaż Grunwaldzki shopping centre is green, as are some buildings of the Wrocław University of Science and Technology. Wrocław was the first city to grant tax breaks to residents with green roofs and walls. The relevant resolution already came into force in 2015 and was amended in 2021 and will be in force until 31 December 2027.

This can certainly be an incentive to build new eco-roofs, especially as there is increasing talk that there should be as many as possible.

That's right. Green roofs are needed first and foremost because of the role they play in the processes of mitigation and adaptation to ongoing climate change. Of course, there are many ways of doing things, but green roofs are the only tool that works on so many levels. However, it is important to remember that their presence must not be an excuse to reduce natural green spaces. Green roofs are a cure for the deficit of plants and should be treated as such.

Are costs the biggest obstacle to their creation?

They are certainly an obstacle, but it is important to remember that these costs pay off after a while, especially in the case of multi-family developments. The problem is rather a lack of proper knowledge and bad examples. A properly constructed green roof has the same durability as a building, it has no right to leak or create stagnant water. And these are concerns that can also be encountered quite often.

You are actively involved in the Polish Green Roofs Association. What are the main objectives of this organisation?

The main objective is, of course, to promote the idea of creating green buildings, which we do in many ways: we organise training courses, workshops, conferences, our members write articles for trade and popular magazines, we also serve cities as substantive support, and we implement grants in cooperation with cities. We have also invited the Wrocław University of Environmental and Life Sciences to participate in one such grant, which is currently being implemented in cooperation with the city of Konin. The association's role in this grant is to organise the educational part, while employees of the UPWr Department of Landscape Architecture are involved in the design work for as many as eight areas located in different parts of the city, including the historic Market Square. This year saw the start of the first two sites designed by UPWr staff and students.

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  UPWr guest Luigi Petito: Green infrastructure is not a trend but a necessity

  Luigi Petito, founder of Business Solutions Europa, who on a daily basis works with the World Green Infrastructure Network, talks about the relevance of green infrastructure to the EU's work on directives implementing its expansion in Europe. At UPWr he was guest speaker at the conference 'Greening the roofs of Polish cities'.