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Calculation Examples

Each plot of land can be designed in various ways. In principle, measures that lead to an expansion of the area of vegetation on the ground are given priority. Only then should additional possibilities, such as the replacement of asphalt and concrete with other surfaces, be utilized.

In the following example a plot of land with residential units, a total area of 740 m² and 330 m² coverage shall be developed according to the BAF because of alterations in the construction. From the degree of coverage follows a BAF of 0.45.

  • Land area

    750 m²

  • Developed area

    330 m²

  • Undeveloped area

    420 m²

  • Degree of development

    0,43

  • Target BAF

    0.45

Calculation: BAF Groundstate

Most of the undeveloped area consists of court or parking space that are sealed or partially sealed. The rainfall drains into the canalization and the effect of the small vegetation is minor.

Enlarge photo: Berechnung BFF-Bestand
BFF-Bestand
Types of surface Area (m²) Weight in factor BAF-Area (m²)
Sealed surface 262 0 0
Partially sealed surface 142 0.1 14
Surfaces with vegetation, connected to the soil below 16 1 16
Total 30

Biotope Area Factor (Ground State) = 30 : 750 = 0.04

Achieving the targeted BAF of 0.45 will require measures that amount to a BAF of 0.41.

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BAF Variant 1

Through unsealing the parking space new room for more vegetation area becomes available, which has important ecosystem services, increase the wellbeing of the residents and allow rainwater collected from buildings to infiltrate into soil. Beforehand partially sealed surfaces are developed to semi-open or greened surfaces.

Enlarge photo: Planungsvariante 1
Planungsvariante 1
Types of surface Area (m²) Weight in factor BAF-Area (m²)
Partially sealed surface 32 0.1 3
Semi-open surfaces 48 0.2 10
Greened surfaces 80 0.4 32
Surfaces with vegetation, connected to the soil below 230 1 230
Rainwater infiltration 320 0.2 64
Total 339

Biotope Area Factor = 339 : 750 = 0.45

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BAF Variant 2

For the construction of a playground and a bicycle carport the proportion of semi-open surfaces are increased and vegetation area is reduced. Nevertheless, to still reach the targeted BAF, the roofs and walls of the outbuildings are greened. In addition, one building gets an intensive roof greening for the collaborative use of all residents.

Enlarge photo: Planungsvariante 2
Planungsvariante 2
Types of surface Area (m²) Weight in factor BAF-Area (m²)
Partially sealed surface 32 0.1 3
Semi-open surfaces 78 0.2 16
Greened surfaces 80 0.4 32
Surfaces with vegetation, connected to the soil below 176 0.8* 141
Rainwater infiltration 220 0.2 44
Extensive roofgreening 35 0.5 18
Intensive roofgreening 100 0.8 80
Vertical greenery with connection to the ground 15 0.5 8
Total 342

*Because of the establishment of a low vegetation volume when a higher volume would be possible the weighting factor is reduced.

Biotope Area Factor = 342 : 750 = 0.45

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BAF Variant 3

For a new structure on the same plot of land the targeted BAF increases to 0.6, independent from the degree of development. Because of the needed reduction of vegetation area, it is necessary to establish more greening of roofs and walls. An optimized system of ways reduced sealed surfaces and a high substrate thickness allows high vegetation volumes even without connection to the soil below.

Enlarge photo: Planungsvariante 3
Planungsvariante 3
Types of surface Area (m²) Weight in factor BAF-Area (m²)
Partially sealed surface 25 0.1 3
Semi-open surfaces 54 0.2 11
Greened surfaces 59 0.4 24
Surfaces with vegetation, connected to the soil below 40 1.0 40
Water surface 10 0.5 5
Semi-intensive roofgreening 225 0.7 158
Intensive roofgreening 100 0.8 80
Vertical greenery with connection to the ground 20 0.5 10
Vertical greenery without connection to the ground 100 0.7 70
Total 457

Biotope Area Factor = 457 : 750 = 0.6

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