Case Löyly

The Löyly, a modern architectural wonder located in Helsinki, Finland, has been recognised as one of the World's 100 Greatest Places to visit list by Time Magazine. 

  • Thermal wood treatment
  • Mechanical wood modification
  • Small Diameter Wood


  • Finland is well-known for its saunas and the Finns passion for timber architecture.  

    In 2016, these two were merged together to create the Löyly which has since become the crown jewel of Helsinki’s waterfront and one of Finland’s finest architectural achievements. This ambitious project was achieved with the help of Avant Wood’s Thermo-Mechanical Timber Modification (TMTM). 

The Challenge 

  • The Löyly was intended to be unique and magical in its own way. The design and location were all carefully considered. However, the use of timber was central to the building’s aesthetics, functionality and charm. 

    At the initial meeting between the developers and Pekka Ritvanen, Avant Wood’s Chief Technology Officer, it was clear that the timber was to be sourced from small-diameter wood that otherwise would have been used in low-value applications. Birch and pine were recommended to reduce costs. As an added challenge, construction was set to begin in two weeks.  

    Pekka knew he had the solution that would solve a major challenge that the developers faced to complete the landmark project.  Avant Wood’s Thermo-Mechanical Timber Modification (TMTM) is a Finnish technology that merges thermal treatment and mechanical modification to quickly and efficiently improve wood properties.  

    TMTM is able to utilize small diameter wood and softwood species, and enhance their strength and density. This enables the use of birch and pine as affordable alternatives to harder species like oak.  

    It only took the TMTM 6 days to prepare the two 2-meter long table-sized samples according to Pekka. The small-diameter birch and pine wood was acquired in 2 days from local plywood producers. On the 3rd day, modification began. It took 2 days for the samples to be dried and another 2 days for final modifications.   

    The developers tested the sample by sawing from various angles and were very pleased with the quality and the efficiency in the production of the wood samples. This led to Avant Wood supplying the much needed timber for the project. 

Avant Wood Löyly

The Result


    Avant Wood supplied all the 6000 wood planks required to complete the project. Most of the planks were used on the exterior which serves like a towel over the glass building inside. It gave the Löyly character and the iconic wood aesthetics that changes color depending on the time of day and the weather. Avant Wood also produced the wood used for the doors, tables, and lockers.  

    The efficiency of producing the wood is also an important point to make. Birch and pine are fast growing species that TMTM can modify to acquire similar strength and density properties as oak. In addition, TMTM can modify the wood 90% faster than conventional machines, which means fewer energy needed to perform the drying and wood densification.  

    The construction of the Löyly with its unique wood material is evidence that wooden buildings are a sustainable way to go. By using small diameter wood, the building was able to store approximately 279 tons of carbon. If the Löyly was made of concrete, it would have emitted 341 tons of carbon during the production of the concrete. This is a total carbon savings of 620 tons.

  • (Carbon calculation based on

Avant Wood Löyly
Avant Wood Löyly
Pekka Ritvanen
Pekka Ritvanen
Klaus Goecke_CEO_Avant_Wood
Klaus Goecke
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