Brown green roofs
Brown roofs / biodiverse roofs are structures that are distinguished by the diverse species composition of plants which green the roof and have also diversely shaped substrates. The soil substrate is modeled to create raised and lowered spaces (numerous hills and holes), allowing for the formation of differentiated habitats where different plant species will grow. Additional components such as large stones or logs of wood are also placed on the roof. They serve as feeding places for numerous insects that will inhabit the roof. This will in turn attract a large number of bird species which can use this space as a safe place to set up a nest – birds will also contribute to the modification of the plant species composition on the roof, which will stimulate the succession process. Brown roofs are populated by species for which these conditions are favorable. The species composition may change continuously. Brown roofs are to restore or create new ecosystems for local species which have lost their habitats (insects, birds and plants) as a result of urbanization.
They are also inexpensive in their design and in subsequent care.
Construction:
– The roof is constructed from two layers of soil, the first one being a mineral or aggregate substrate with low nutrient content. This layer is coated with local (habitat) soil – allowing local habitats to be created on roofs (as there are specific micro-organisms, insects or plant seeds in the soil).
– It is important to vary the roof shape to obtain lower and higher ground conditions. This allows the creation of specific, differentiated habitats. Some plants prefer a larger thickness of substrate, while others can develop well in a small amount of substrate..
– Stones and logs are placed on the roof shaped in this way. Below them, various species of insects will find habitats, which in turn attracts birds to the roof. Birds visiting the roof will also eagerly sit on tree limbs.
– Greening by sowing plants. Perennials, shrubs and trees can be used.
– A brown roof has a specific appearance, so it is important to work with local communities to appreciate the natural beauty of the concept.
Features:
Creating natural habitats for birds and insects, enhancing urban biodiversity.
Sources and additional information:
http://www.urbanhabitats.org/v04n01/urbanhabitats_v04n01_pdf.pdf
http://singleply.co.uk/wp-content/uploads/2013/04/fact-sheet-brown-_biodiverse_-roofs.pdf
Rogers J., 2013, Green, brown or grey: Green roofs as ‘sustainable’ infrastructure, Sustainable Development and Planning, 173, s. 323 – 332
A brown roof on a green building in Pasłęk:
The brown roof was installed, i.a., on an ecological building made from soil in Pasłęk. The roof is characterized by low thickness of the soil substrate, as it has had to be very light so that its weight can be lifted by a wooden roof covering the building. The current greening of the roof is the result of the succession process. Initially, the roof was to be greened by sedum and houseleek seedlings, but these plants did not catch on (they froze during the winter), so it was decided that the roof should be covered with greenery itself, thanks to the succession process. Within two years, the roof was covered with various species of sedum, houseleeks and mosses. This optimal greening makes the surface resistant to changing weather conditions. It also does not require any essential care treatments.
