The Greenest of the Green block, Helsinki, Finland

The kitchen garden. Photo: Taina Suonio
Area characterisation: 

Helsinki, the capital of Finland with a population of appr. 650 000, is the 3rd largest city in the Nordic countries. It is situated on the shore of the Gulf of Finland: humid continental climate, the temperature ranging from -5 (winter) to 19-22 C degrees (summer), on average. Population density in the inner-city area reaches over 16,000 inhabitants per km2; the rest of the city is more sparsely populated. Helsinki is growing fast, and new residential areas are densely built. Thus, the quality and accessibility of the green spaces are important. The Jätkäsaari-area where this case, The Greenest of the Green, is situated (100 ha, under construction 2003–2030, residents total 21,000) is next to the Baltic Sea, meaning harsh environmental conditions (wind, sun) for the vegetation.


On top of the block of 121 apartments, there are six different green roofs/ roof gardens: two meadow roofs for supporting biodiversity, two berry and fruit forests and a kitchen garden with planting boxes and a big green house. All green roofs are accessible. The green facades consist of ‘green balconies’, i.e. planting boxes with conifers and climbers, and ground-level climbers. In addition, there is a court yard garden and a sunken garden with trees, ferns and mosses The kitchen garden has 52 planting boxes (1m x 1m) for the residents to cultivate. Photo: Taina Suonio In the green house, residents gather around the big table for e.g. ‘seedling parties’. Shared green spaces are meant to support social interaction. Photo: Marja Mesimäki Construction of the green facades: planting box. Photo: Marja Mesimäki Construction of the kitchen garden. Photo: Marja Mesimäki The block is next to the Southern harbor of Helsinki. In the green house, the plants grown by the residents flourish in the beginning of June. Photo: Marja Mesimäki. The kitchen garden allows the cultivation of herbs, vegetables, root vegetables, and decorative plants. There are five composters for the plant waste, to keep the cultivation sustainable.  Photo: Taina Suonio Based on the action research conducted in the block, the residents have formed a group of active gardeners that organizes the cultivation by, events. The cultivation is based on community gardening, i.e. the group cultivates all boxes together, share responsibilities and experiences, and learn from each other. The activities are open to all residents: anyone can join. The costs of cultivation (seeds, plants), and crops are shared among the group and partly among all residents.   Photo: MM Several workshops have been organized by the research project, to co-design the uses of the shared green spaces, and to create a common value-base, emphasizing e.g. equity, joint learning, inclusiveness, positive atmosphere and mutual understanding. By involving, empowering and respecting the residents (Appreciative Inquiry -approach), a better commitment for taking care of the shared spaces is achieved. Photo: Marja Mesimäki The gardening group has grown plants for the kitchen garden from seeds. Photo: Anneli Kangas-Kärki. On all green roofs of the block, Finnish native species are favored, for example (Leucanthemum vulgare) Oxeye daisy.(Silene viscaria) Sticky catchfly, (Trifolium repens) White clover, (Lotus corniculatus) Bird´s-foot Trefoil/Common Birdsfoot Trefoil, (Fragaria vesca) Wild strawberry, (Galium verum) Lady´s bedstraw (VU Vulnerable), (Anthoxanthum odoratum) sweet vernal grass, holy grass, vanilla grass, (Dianthus deltoides) (NT, Near threatened) Maiden pink. Photo: Marja Mesimäki There are several ‘biodiversity hotspots’ in the block, below one on the meadow roof. Photos: Marja Mesimäki The furniture on the roof is fastened for safety reasons. Photo: Marja Mesimäki The climbers (part of the evolving green facades) survived the first winter surprisingly well. Photo: Marja Mesimäki An experimental moss wall and a moss garden were constructed in the garage (sunken yard). Photo: Juhamatti Niemi-kapee Moss garden. Photo: Juhamatti Niemi-Kapee

The objective of the project is to investigate the future possibilities of green area development, by exploring the functionality of green areas on the roofs of apartment buildings and to gain insight into the impacts green roofs may have on housing and the sense of community.


The block is a life-size scientific research design on real buildings. The main research questions are:

1)    Do the green facades protect the buildings from heavy rain, heat or other weather conditions? This is measured with automatic measuring device, in cooperation with the Tampere University of Technology.

2)    How are the plants managing in the challenging conditions at the seashore? This is being studied by monitoring the growth and survival of the vegetation. The plants primarily consist of traditional plants and plants found in Finnish nature. Harmful invasive species have been excluded (cf. NOBANIS invasive species database). The vegetation comprises a wide selection of different species and their cultivated varieties. The idea has been to find the most tenacious of the species, as the resiliency of different species and cultivars can vary. The study also covers the use of moss as part of green area development.

3) How do the residents adopt the shared green spaces? What kinds of experiences do the spaces offer, and can they help supporting social cohesion? The uses of the various green roofs are being developed through action research/co-design, to meet the needs of the residents.

Potential impacts/benefits: 

The information collected in The Greenest of the Green project will help to design ecologically and socially sustainable nature-based solutions.


The climatic conditions in Jätkäsaari are challenging for green roofs and facades, offering a unique opportunity to study how plants succeed in wind and heat, and thus producing knowledge for preparing for the changing climate. Green roofs and facades of the block cool down the microclimate on roofs, as well as roof and wall structures. The green roofs with thick substrate also help with maintaining storm waters. Circular economy has been considered in material selection – plastics have been avoided in all green roof layers. Composts offer possibilities for circulating the plant waste from all roofs. Plant-beneficial microbes are being studied on the roofs, as a means to support the well-being of the plants without adding nutrients that are harmful for the water quality in the sea.


The urban planning policy of the city of Helsinki is to tackle segregation by locating different housing in the same area (private ownership, rental, supported housing). In this project, special emphasis is on offering various shared green spaces for supported housing and enhancing social cohesion and sense of community. The block consists of 66 supported rental apartments and 55 supported right of occupancy apartments, with altogether appr. 230 residents. As Jätkäsaari area is very densely built, and under construction for years to come (until 2030), the green area services are very limited in the vicinity of the block. The green spaces on roofs offer beneficial nature experiences and possibilities for gardening without using transportation, which supports environmental responsibility.

NbS benefits 
  • Reduce run-off
  • Reducing temperature at meso or micro scale
  • Developing climate change mitigation
  • Improve connectivity and functionality of green and blue infrastructures
  • Increase achievements of biodiversity targets
  • Increase Biodiversity
  • Increase quality and quantity of green and blue infrastructures
  • Increased cultural richness and biodiversity
  • Enhancing sustainable urbanisation
  • Changing image of the urban environment
  • Increase accessibility to green open spaces
  • Increase amount of green open spaces for residents
  • Increase awareness of NBS solution & their effectiveness and co benefits
  • Increase communities’ sense of ownership
  • Increase social interaction
  • Increase stakeholder awareness & knowledge about NBS
  • Increase well-being
  • Increase willingness to invest in NBS
  • Provision of health benefits
  • Social inclusion
  • Social learning about location & importance of NBS
Transferability of the result: 

The project is part of the ‘Developing blocks of flats’ -program of the City of Helsinki, offering channels for communicating the results for future development projects in the Helsinki Metropolitan area with over 1,1 million inhabitants. In a broader context, the ecological and technical results can be applied in cities in the Nordic and Baltic countries (Northern Temperate Region). The results for the possibilities of the shared green spaces on roofs to strengthen social cohesion are widely applicable.

Lessons learned: 

The involvement of academic research in a real planning and construction process requires:

  • proper stakeholder mapping in the beginning (chains of command, responsibilities etc.)

·       multi-channel communication in every phase among all stakeholders

  • involving researchers in the very beginning, and sharing the objectives, principles and practicalities of the academic research among all stakeholders in an understandable way among all stakeholders.

The vegetation was planted autumn 2017, and the first spring/ early summer 2018 showed that majority of the appr. 100 planted species survived the very challenging winter 2017-2018. The co-design workshops produced a solid value-base for the activities and uses of the shared green spaces. The results so far show that successful community gardening on roof is possible and supports social interaction and sense of community in a block of flats.


TA Companies financed the planning and construction of the block, with support from The Housing Finance and Development Centre of Finland (ARA) that is a governmental agency to implement social housing policy.

The research is financed by TA Companies and Maj and Tor Nessling Foundation.


Taina Suonio

Susanna Lehvävirta

Marja Mesimäki