Thursday. 07.12.2023

Research team aims to build in Helsinki tallest wooden apartment tower

Right now, the world's tallest wooden block is an 18-storey wooden tower of flats in Norway. The project designed by Finnish experts is for a 30-storey tower which would be built in the Finnish capital city.
Image: Architectural design by Harry Edelman, Structural design by Sami Pajunen and Janne Hautala, Urban Landscape

Would you like to live in a 30-floor wooden apartment block in Helsinki?

It would be possible according to Harry Edelman, head of the Sustainable Building Research Group at the University of Tampere.

Wood construction has begun to be developed as an environmentally friendly alternative to the prevailing building methods. Although in recent years the enthusiasm for wood has returned, the construction of multi-storey wooden houses in Finland has long been poor.

Especially in late 1960's the wood construction lost its popularity because of the concerns about fire safety and the rise of concrete. But Harry Edelman and his team have solved many problems of the wood construction. When wooden apartments are at stake, everybody first asks the same question: "What about safety?"

When asked about fire safety, Harry Edelman said that, "Fire safety is a very important topic. Both active and passive measures are needed. Sprinkler system based on fine particles of fog work efficiently against fire without a hazard of extensive water damage in case of false alarm. Further, some non-combustible surface materials are needed to increase the fire safety and comply with the regulation. It is not necessary that the entire building is made out wood only, even though the majority of material is wood providing the climate benefits and also enabling the prefabrication of the building."

Building a 30-storey wooden tower in Helsinki is a major task. For Edelman, "Helsinki is a fast growing urban hub and taller buildings can be fitted to its urban context in particular in transit hubs such as rail and metro lines. The Nordic Tower concept offers a solution for the prefab mid-rise residential buildings –from affordable housing to high-end developments depending on the each case and urban development need. The structural system needs to be viable also for taller buildings. Helsinki would provide a great example and lead the way in the fight against the climate change and making a true change. The development would surely attract a great number of visitors as well."

Carbon negative

The structural system of a wooden apartment building solution is standardized, but the architecture around it is free. The most important thing, according to Edelman, is that construction is carbon negative and in line with the principles of the circular economy. Tall buildings are also the future of urbanization, especially in the world.

 "Primarely wood is proposed as material while if offers both benefits for carbon neutrality and efficient off-site industrial manufacturing. And due to the weight of the wood it is also feasible to transport. The downside of the wood is on the other hand the weight which calls for measures in terms of stability. We've design a special steel cable system comparable to a rigging of a sailing yacht. It allows to reduce the vibration caused by the wind. Additionally, heavy materials such as recycled concrete could be used on the floors to increase the weight and also improve the acoustic performance" says Edelman.

Right now, the world's tallest wooden apartment block is an 18-storey wooden block of flats in Norway. However, the project of building a 30-story wooden apartment block in Helsinki might face another problem: wind. Wood is a particularly light material, which is why the high-rise wooden buildings are particularly affected by the wind.

The problems with wind

But the research group claims to have a solution for that. According to Edelman, "the structural system contains four vertical shafts that allow a cable system to contribute the reduction of vibration and acceleration of the building during heavy winds. The cable system is connected to the elevator shaft at the upper part of the building. Thus it resembles a bit like the rigging of super-sized sail yacht

The mechanics of the structure have been calculated having the core of the building, that is the cross-laminated-timber elevator shaft, functioning as the key component for resisting the wind. Clearly, the prefab residential units contribute to the system but those bear basically only their own load without contributing overall wind resistance. The system benefits also from increasing the weight of the building between the floor slabs, for example, by using recycled concrete."

The designers admit that a brand new construction concept cannot be completely risk-free. The project has been funded by Business Finland.

Research team aims to build in Helsinki tallest wooden apartment tower