Salzburg uses mathematical formula to push for more green spaces

The city is a pioneer in developing the new ecological framework that will provide fair and transparent green obligations for new development

Yesterday, the city of Salzburg in Austria presented GrünFZ - a new framework for calculating the amount of greenery a newly constructed building should have. The Institute for Landscape Planning of the University of Natural Resources and Life Sciences in Vienna (BOKU) developed the concept, using a mathematical formula considering a building’s living space and surface area as well as variables, such as nearby trees.

According to the deputy mayor of Salzburg Barbara Unterkofler, this framework will contribute to a transparent, fair and streamlined approach to greening the city – a major priority for the current administration.

Leading the way in climate change adaptation in Austria

Local authorities were adamant that this is the first time a city in Austria uses anything resembling an algorithm on how much green space a new construction project needs.

Every new construction project in the city will have to use the framework to determine the amount of greenery that should be added to the building. The project should accommodate green roofs, green façade and green spaces around the structure.

At the same time, the framework can help in determining the exact type of greenery, as it considers trees, green roofs and grass lawns as multipliers. Each element in the green infrastructure has its own assigned scientific weight, respective to its ecological impact.

This is one of the main contributions of BOKU, as they used their expertise to conduct a research project to determine the benefits and drawbacks of the green elements.

Flexible formula for a greener future

The target value of greenery under GrünFZ is primarily determined by the size of the construction project, and the framework envisions three categories:

• Smaller construction projects: Detached single-family houses and terraced houses;
• Medium-sized construction projects: more than 5 apartments or 500 m² gross floor area;
• Large building projects: over 2,000 m² gross floor area.

A visualisation of the green formula, Source: City of Salzburg

The actual calculation of the necessary greenspace will be simple and will happen through an Excel spreadsheet provided by the city. First, planners will have to input some basic information, such as floor area, façade area and roof area. Then they have to add the green proposal to the mix: number of trees, lawn area and etc.

After that, the spreadsheet will do the calculation and determine whether the project reaches the targeted green value. Developers will have to submit the GrünFZ spreadsheet along with the building plan when applying for a permit from the city.

Barbara Unterkofler was quoted in a press release as saying: “Early and active adaptation to developments in climate change is essential. This is our responsibility to the citizens now and future generations as well. It is particularly important to me that we do not let things play out and come to us, but that we take action".