Puukuokka Housing Block

The Puukuokka Block is an energy-efficient and ecological trio of multistory wood-framed apartment buildings in the Jyväskylä suburb of Kuokkala. Finished in the spring of 2015, Puukuokka One was the first eight-story high wooden apartment building in Finland. Puukuokka Two followed in 2017, and with the completion of the Puukuokka Three in 2018, the entire Puukuokka Block is now ready. The Puukuokka complex offers homes for 186 households from single dwellers of all ages to families with children.

The Puukuokka Block explores the potential of modular prefabricated CLT construction to provide environmentally responsible and affordable housing of high quality. Puukuokka attempts to make the best possible use of the technical and aesthetic qualities of CLT and to create a wooden building in large scale with a distinct architectonic expression of its own. The block also pilots an innovative lease-to-own financing strategy that aims to support social sustainability by promoting stable communities. The Puukuok ka housing has been extremely well received by the residents who praise it for creating a comfortable living environment with an excellent framework for a friendly and socially stable neighbourhood.

Puukuokka served as a pilot case to develop a CLT based system of volumetric modules. During the design process, energy calculations and LCA analysis were carried out in order to develop the design. Different solutions were tested to create a multi-story apartment building using the basic modular structure as the starting point. The entire load bearing structure and frame of the Puukuokka buildings is made of massive wood and composed of prefabricated volumetric CLT modules. Each apartment is composed of two modules, one housing the living room, the balcony and the bedroom, the other housing the bathroom, the kitchen and the foyer area. The recessed balconies bring light to the interiors and separate different functional areas in the apartments.

The optimization of the entire production and construction process was an important aspect taken into consideration in the design process. The prefabrication of the modules made it possible to minimize the period of construction on site, and also allowed for production in controlled indoor conditions in the factory thus significantly reducing the risk of exposure to weather conditions and humidity of the structure during construction. Also the wooden façade elements were prefabricated and brought to the site as elements ready for installation. The hallway, also made of CLT, is the only part of the building that is fully constructed on site. The piping for heat, water, electricity and ventilation is integrated in the technical wall of the hallway, making it easily accessible for maintenance.

The maximum possible dimensions of the volumetric CLT modules were carefully taken into consideration in the design. There were two factors limiting the maximum possible dimensions: the capacity of the local factory in Hartola where the volumetric modules were prefabricated determined the maximum size possible to produce; and the local regulations regarding the maximum width and length of the loads allowable for transportation by truck on the highways set limitations on the size of the modules to be transported.

Working with CLT enabled several important aspects in the project: Thanks to the insulating qualities of massive wood, it is possible to achieve a high level of energy efficiency in a building with a fully wooden frame and structure. These qualities made it possible to create a spacious hallway with a full height atrium and a lot of light with a semi-warm room temperature, lower than what would be ideal inside the apartments, without impacting the temperature level of the apartments. This naturally amounts to savings in energy use and is particularly pertinent in the Nordic climate with cold winters. Furthermore, a system for individually controlling the temperature levels in each apartment unit further enhances the energy efficiency of the building.