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Calculating the BAF

The BAF expresses the ratio of the ecologically effective surface area to the total land area.

BAF = ecologically-effective surface areas ÷ total land area

In this calculation, the individual parts of a plot of land are weighted according to their “ecological value”.

Types of surfaces and weighting factors per m2

  • Sealed surfaces
    (Weighting factor 0,0 per m²)

    Surface is impermeable to air and water and has no plant growth (e.g., concrete, asphalt, slabs with a solid subbase)

  • Partially sealed surfaces
    (Weighting factor 0,3 per m²)

    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)

  • Semi-open surfaces
    (Weighting factor 0,5 per m²)

    Surface is permeable to water and air, water infiltration and plant growth (e.g., gravel with grass, wooden cobbles, grass paving blocks)

  • Surfaces with vegetation, unconnected to the soil below
    (Weighting factor 0,5 per m²)

    Surfaces with vegetation that have no connection to the ground and less than 80 cm of soil covering

  • Surfaces with vegetation, unconnected to the soil below
    (Weighting factor 0,7 per m²)

    Surfaces with vegetation that have no connection to the ground but more than 80 cm of soil covering

  • Surfaces with vegetation, connected to the soil below
    (Weighting factor 1,0 per m²)

    Vegetation connected to soil below, available for development of flora and fauna

  • Rainwater infiltration per m² of roof area
    (Weighting factor 0,2 per m²)

    Rainwater infiltration for replenishment of groundwater; infiltration over surfaces with existing vegetation

  • Vertical greenery with connection to the ground
    (Weighting factor 0,5 per m²)

    Direct connection of the vertical greenery with the soil, supply with nutrients and water directly over the roots in the soil

  • Vertical greenery without connection to the ground
    (Weighting factor 0,7 per m²)
    since December 2019**

    Vertical or horizontal vegetation on a wall without direct connection to soil on the ground, permanent planters supplying the vegetation areas, artificial irrigation

  • Extensive roof greening
    (Weighting factor 0,5 per m²)
    since December 2019*

    Nature-like design of the roof surfaces with a substrate thickness ˂ 20 cm without artificial irrigation

  • Semi-intensive roof greening
    (Weighting factor 0,7 per m²)

    Mixture of extensive and intensive roof greening with a substrate thickness › 12 cm (depending on the chosen plantings), usually in combination with artificial irrigation

  • Intensive roof greening
    (Weighting factor 0,8 per m²)
    since December 2019*

    Design of the roof similar to ground-based green areas with a substrate thickness › 15 cm, usually in combination with artificial irrigation

*) In December 2019 the surface types for vertical greenery and roof greening were differentiated and can be used for new BAF-landscape plans since then. The previously established BAF-landscape plans refer to the surface types before December 2019 and are valid further on in this version.