The BAF expresses the ratio of the ecologically effective surface area to the total land area.
In this calculation, the individual parts of a plot of land are weighted according to their "ecological value".
Weighting factor /
per m² of surface type
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Description of surface types
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Sealed
surfaces
0.0
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Surface is impermeable to air and water and has no plant growth
(e.g., concrete, asphalt, slabs with a solid subbase)
|
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Partially sealed
surfaces
0.3
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Surface is permeable to water and air;
as a rule, no plant growth
(e.g., clinker brick, mosaic paving, slabs with a sand or gravel subbase)
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Semi-open
surfaces
0.5
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Surface is permeable to water and air;
infiltration; plant growth
(e.g., gravel with grass coverage, wood-block paving, honeycomb brick with grass)
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Surfaces with vegetation,
unconnected to soil below
0.5
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Surfaces with vegetation on cellar covers or underground garages with less than 80 cm of soil covering
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Surfaces with vegetation,
unconnected to soil below
0.7
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Surfaces with vegetation that have no connection to soil below but with more than 80 cm of soil covering
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Surfaces with vegetation,
connected to soil below
1.0
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Vegetation connected to soil below, available for development of flora and fauna
|
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Rainwater infiltration per m² of roof area
0.2
|
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Rainwater infiltration for replenishment of groundwater;
infiltration over surfaces with existing vegetation
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Vertical greenery up to a maximum of 10 m in height
0.5
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Greenery covering walls and outer walls with no windows;
the actual height, up to 10 m, is taken into account
|
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Greenery on rooftop
0.7
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Extensive and intensive coverage of rooftop with greenery
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