Green Area Factor, GAF

A tool for increasing greenery of lots in a dense urban environment

Quick guide

The goal of the green factor approach is to mitigate the effects of construction by maintaining a sufficient level of green infrastructure while enhancing the quality of the remaining vegetation. The significance of green surfaces in the adaptation to climate change raises as the city structure becomes denser.


The green factor method improves the city’s prerequisites for adapting to climate change by promoting the green efficiency of the vegetation on the plots and the conservation of sufficient green structure. Vegetation mitigates the risk of flooding, reserves carbon dioxide, cools down the heat islands of built environments and increases the pleasantness and beneficial health-effects of the urban spaces. In the green factor method, the planner sets a green factor target level for the plot that can be achieved flexibly by the garden designer using various green elements when designing the garden. The method developed for the City of Helsinki provides 43 different green elements relating to planted and maintained vegetation, various run-off water solutions and permeable surfaces, etc. The green factor is calculated as the ratio of the scored green area to lot area. The green factor method has been developed to support the land use planning process, and it is intended particularly for city planners, landscape architects and garden designers. The green factor can, for example, be included in the zoning regulations or used for granting concessions during a construction permit application process.

Learn more about the case – ask and comment in the space below