Lightweight timber construction with a zero-emissions concept

The LOGL, the ‘Landesverband für Obstbau, Garten und Landschaft e. V.’ (State Association for Fruit Growing, Gardening and Landscaping) naturally upholds tradition and the long-standing diversity of garden culture. The preservation of the cultural landscape and the imparting of specialist knowledge are central concerns, while at the same time the association seeks to help shape modern garden culture. It is in this context that the firm Lohrmannarchitekten has built a new LOGL centre of excellence in the small town of Weil der Stadt near the German city of Stuttgart. The building is a kind of modern wooden barn, the lightweight construction of which binds CO2 and releases no emissions during operation.

The property for this building project is located approximately south of the built-up area of Weil der Stadt and is part of a mixed arable-forest landscape. The direct neighbour is the ‘Landesakademie für Jugendbildung’ (State Academy for Youth Education), which is also an institution for the transfer of knowledge. The basic idea for the design was the image of a diversely designed natural garden and an orchard, in which two solitary wooden buildings are embedded. The external appearance of the building is modelled by Lohrmannarchitekten on the wooden barns typical of southern Germany, with a building envelope made of local softwood and a sheet metal-clad roof. The rhythm of the facades is defined by sliding elements that extend up to the height of the eaves, which are an elegant interpretation of a barn door. In addition, however, they also serve as a passive low-tech solution for external and flexibly sliding sun protection. The design basis in the view is a clearly visible base made of reinforced concrete, which is also the building foundation and protects the timber construction from the weather in this area.

Sustainable value chain

The concrete base is also an important part of the interior design. On both the exterior walls and the central staircase, it levels the space from the same height. Only the lift shaft to the upper floor is made entirely of concrete. However, the material that dominates the atmosphere in the interior is wood, in contrast to the building envelope, various types of hardwood and fruitwood. However, the choice of wood types is not purely a design decision. By mixing wood-based materials and wood types, ‘the specific properties of the respective building material can be used in a targeted manner. This is intended to demonstrate in an exemplary way that modern timber construction can combine the wide range of possibilities for using softwood and hardwood in a single project,’ explains Holger Lohrmann. This extensive use of wood as a renewable resource also means that the building can be erected with a comparatively very light construction, which in turn conserves important resources. Equally important to the planning team, however, was the activation of the regional value chain. In other words, regional materials and product manufacturers were chosen as far as possible for the construction of the two wooden houses, and all the tradespeople (and ultimately the architectural firm itself) are from the local area. All of this led to a reduction of CO2 emissions to a minimum during the construction of the centre of excellence.

Building operation with zero emissions

From the outset, the project was planned as a zero-emissions building. The building technology required to operate the visitor centre, most of which is located in the smaller of the two buildings, has been reduced to a reasonable level. The heat for the heating and hot water is generated by an air-to-water heat pump in a monobloc design. The heat pump's inverter technology makes it possible to use it for cooling as well. The waste heat from the device is also used to raise the return temperature, which further increases its efficiency. A photovoltaic system supplies the electricity for the heat pump. The heat pump and the photovoltaic system produce energy and heat during the day, when the building is in most frequent use. In addition, heat is stored in a 200-litre buffer storage tank so that heat for the underfloor heating and for hot water is available even when not enough can be produced. To prevent ventilation heat losses, the interior rooms are ventilated via a small ventilation system with heat recovery. It is not connected to the heat pump, but heats the air electrically in the event of a peak load. There is also a safeguard for the exceptional case of a power supply via a connection to the public grid. The planning team has also considered water as a resource: rainwater is collected in a cistern for watering the garden. The LOGL Competence Centre was recently awarded the ‘Holzbaupreis Baden-Württemberg 2024’, the 2024 Baden-Württemberg Timber Construction Prize.

Project data:

Project: LOGL Kompetenzzentrum (LOGL Competence Centre) in Weil der Stadt

Architecture: lohrmannarchitekten, Stuttgart

Client: Landesverband für Obst, Garten und Landschaft (LOGL) e. V., Weil der Stadt

Structure: FM Engineers, Herrenberg

Building services: Die PlanSchmide, Vaihingen/Enz

Building physics: Bauphysik 5, Backnang

Surveying: Duppel Ingenieurbüro, Rutesheim

Completion: 2023

Location: Am Malersbuckel 11, 71263 Weil der Stadt

© All images: Volker Schrank, Stuttgart