Helsinki now has its first passive wood apartment buildings, which were built for the new residential district of Honkasuo. The two plots, bordered by parks, now house two four-storey and two three-storey apartment buildings, and a wood row house and outdoor equipment storage on each plot. The project included a total of 116 new apartments.
In the spirit of the city zoning plan, the buildings form several rows on an arc. The number of storeys decreases from four on the outer arc to three and one as the buildings descend towards Perhosniitty park. The building roofs also follow this theme of a downward slope towards the park. The row houses on the inner arc zigzag to make room for the needed playgrounds and seating. As required by the city zoning plan, adjacent buildings have differing main colours. The dark vertical panels of the ground floors and the light vertical sheets of the balconies tie the differing colour schemes together. Some of the balcony walls use the main colours of the building to add a little variation to the otherwise light-coloured band of balconies.
The apartment buildings of the initial block in Honkasuo were mostly built using Finnish softwoods. The exterior walls, floors, roofs, balconies and lift shafts all have wood structures. The intermediate building floors mostly use laminated wood and drywall slabs. The facades are constructed from large elements, usually with wood cladding on the outside and drywall in the inside. The wood panels on the ground floor facades are treated to be fire-retardant. The load-bearing structures for the balconies use CLT slabs and dividing walls. CLT structures are also used in the dividing walls and stairwell landings. The flights of stairs are laminated wood stair elements with natural stone surfaces. The visible wood components in the stairwells are treated to be fire-retardant. The roofs are mostly pitched roofs made from roof elements.
The area’s zoning plan presupposes the application of low-energy construction principles, but the Honkasuo wooden apartment buildings were actually able to meet the passive house requirements set by VTT (the Technical Research Centre of Finland Ltd). The bathrooms and toilets in the apartments have underfloor heating with circulating water. The other spaces use warm air heating. Traditional radiators are not required. The heat recovery of the ventilation system is more efficient than usual. The apartments also have water-saving fixtures. The lighting in the common areas uses motion sensors and LED lamps. Solar panels installed on the roofs provide renewable energy. The row of balconies opens up in the best direction to allow them to serve as a protective barrier that provides shade and cools the apartments during hot summers.
Work proceeded swiftly on the site. The element system’s large elements were quick to install during the framing phase. For example, the wood frame of the four-storey apartment building was in place in just four weeks or so. Work inside the building was able to start once any necessary elements had been installed, which meant that different work phases were able to make headway in parallel. Weather protection attached to an electric motor was hoisted up with alongside the framework to keep the worksite dry and clean.