Building planning always involves the question of the relationship between architecture and nature, and one of the concepts that order this relationship is the biological index, more commonly found as an indicator of biologically active surface. It determines what part of the plot must remain an area allowing natural vegetation and water retention, that is, naturally active land.
In practice, the biologically active area mainly includes fragments of the plot covered with greenery, such as lawns, gardens, flower beds or unpaved areas. In certain cases, intermediate elements are also taken into account, for example green roofs or terraces with an appropriate layer of soil, as long as they meet the requirements laid down in local regulations. Each municipality may define slightly differently what exactly goes into this balance sheet, so it is always necessary to analyze the current findings.
The role of the biological indicator goes beyond aesthetics. Its objective is to protect the environment and the quality of the space by reducing excessive sealing of the site. An adequate share of green space affects the microclimate, stormwater management and comfort of use of the plot, especially in dense urban or suburban buildings. From the perspective of architectural design, this parameter has a real impact on the way the site is developed. The high required biological index can force a more compact body of the building, the abandonment of extensive driveways or a change in the layout of communications on the plot. Low values give more freedom, but still remain linked to other planning constraints, such as building lines or the building intensity index.
The source of valid values are planning documents. Information on the minimum share of biologically active area can be found in the local zoning plan or in the decision on building conditions. The omission of this provision or its incorrect interpretation may lead to the need to correct the design already at the formal stage. The importance of a biological indicator is best seen when it becomes an element of conscious design and not just a requirement to be fulfilled. The skillful combination of architecture with greenery allows you to create spaces that are more welcoming, functional and resistant to climate change, while remaining compliant with regulations.
