Green factor – tool for increasing urban green

A significant part of urban green is located in city blocks and on plots. Espoo’s Green Factor Tool aims to guide the planning of plots and city blocks towards more sustainable and greener solutions. The purpose of the tool is to ensure the comfort of gardens and courtyards and support biodiversity, city residents’ well-being and the natural management of storm water. The Green Factor Tool gives a plot a set of target levels that can be achieved with different green construction solutions. The tool can be used to support planning, as it helps make good and sustainable planning solutions for the green structure.

Espoo’s Green Factor Tool is based on the Excel-based tool developed in the Climate-proof city (Ilmastokestävä kaupunki, ILKKA) project in 2014. The Green Factor Tool is in use in several major cities in Finland. In Espoo, the use of the Green Factor Tool has been piloted in detailed planning since 2018. Read more about the development of Espoo’s Green Factor Tool: Espoo’s city bloc-specific green factor reports 2023 (PDF, in Finnish)(external link, opens in a new window)

The Espoo City Council decided on the use of the green factor in the Housing and Land Use Principles on 12 June 2023. According to the decision, the city will, where possible, utilise the green factor in planning. The development and promotion of the Green Factor Tool is also recorded in the Espoo Climate Watch and Espoo’s action plan for adaptation to climate change 2022–2025. It has also been recorded as a practice to be developed in the Action Programme for Biodiversity. 

The City Planning Committee decided on the introduction of the tool and the related target levels in its meeting on 13 November 2024. Prior to that, the tool and its target levels were made available for public review and commenting from 9 September to 8 October 2024.

Espoo’s Green Factor Tool includes three objectives and their indicators.  

The green factor target describes the green factor of the plot, that is, how many different green structures and vegetation the plot must have. The target level of the green factor is determined according to whether it is an area used for residential housing, services, commerce, industrial activities or parking. The target level can be achieved with several different solutions. 

In the calculation, the different green structures of the plot are weighted differently. Green structures include trees to be kept and trees to be planted as well as shrubs, grass areas and other vegetation. The weighting of green elements has taken into account ecology, functionality, landscape value, maintenance requirements, and the quantitative and qualitative management of storm water. Weighting means that some green structures are more effective than others when viewed from these perspectives. For example, any trees kept and planted on the plot, as well as natural storm water structures, receive a higher weight in the Green Factor Tool.

Finally, the calculation gives the entire plot a green factor value that can be compared with the target level of the calculator. The green factor value is the total of areas of vegetation and storm water retention solutions, which are weighted as described above. This weighted area is then divided by the area of the plot.

The storm water calculation of the green factor shows

• how much storm water is generated from the plot
• how much the storm water structures planned for the plot would retain storm water
• how much storm water is left unretained in relation to the plot’s retention volume need.

The retention need is usually defined in the detailed plan and it is entered as initial data into the green factor calculator. The tool prepares the storm water calculation based on the entered green elements. The storm water target and calculation are based on Espoo’s storm water programme.  
 

The Green Factor Tool also includes a nature calculator. It demonstrates how well the green structures of the plot support biodiversity.

The calculator takes into account five different categories:

• multi-species and multi-layered vegetation
• species endemicity
• measures to increase the amount of decayed wood
• supporting fauna by providing nests and habitats
• utilisation of blooming and harvest-yielding species.

The achievement of solutions that promote biodiversity is described in the calculator with verbal descriptions according to how well the entity supports biodiversity. The result of the nature calculator is not dependent on surface areas in the same way as the result of the green factor, so the target level of the nature calculator is the same for all land use types. The target level can be achieved with several different solutions. 

During the development phase of the tool, test calculations were made to survey the typical green factor of Espoo and to define the target levels of the green factor and the nature calculator. The aim was to set the target levels so that they can be achieved with several different implementation options. However, the goals cannot be achieved without a significant amount of vegetation, green structure or storm water solutions. 

Target levels for green factor are

• in residential areas dominated by detached houses 1.0
• in residential areas dominated by blocks of flats 0.9
• in areas of services and office construction 0.8
• in areas of commerce and commercial construction 0.7
• in areas of industrial operations and logistics 0.5.

In parking facility and parking space areas, the target level is determined by the target level of the type of land use that the area mainly serves.   

Based on the test calculations, a target level was determined for the nature calculator. This level is suitable for the built environment, but at the same time supports the city’s nature-wise objectives, adaptation to climate change and nature-oriented character.

In order for a plot to reach the target level "Solutions for green elements support biodiversity", it must receive at least 5 points in the calculation (maximum 18.5 points). The starting point for the target level was that construction usually has a negative impact on biodiversity, but with different solutions and choices it is possible to mitigate harmful effects and support the development of new nature values. 

The green factor is used by builders and designers as well as the city’s detailed planning and Building Control in the various phases of planning. The user manual for Espoo’s green factor provides more detailed instructions on the use of the tool. The use of the tool is ruled by the detailed plan.

Detailed planning work produces a reference or block plan that includes making a green factor calculation. The calculation is displayed on the green factor scorecard, which is added as an appendix to the plan summary.

An examination of the detailed plan might state that achieving the target level of the green factor is not possible. In this case, the plan provides plan regulations for green elements. These regulations are more specific than the green factor. The nature calculator is filled in only at the building permit stage. 

At the building permit stage, the builder draws up a green factor calculation based on the project’s yard plan. The calculation is attached to the site’s building permit application. At Building Control, an employee tasked with processing permits reviews the site’s green factor indicated on the scorecard to check that the site meets the target levels set for the green factor and nature calculator.  

The use of the Green Factor Tool does not apply to public areas such as parks or streets.  

You may download the Green Factor Tool and its instructions from the City of Espoo’s databank(external link, opens in a new window). The material is provided only in Finnish. The tool is Excel-based and works best with Excel. The tool is not accessible.