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Swiss wood school house

19.11.2021

National Councillor Erich von Siebenthal and Thomas Lüthi from the Initiative Holz BE presented the certificate to the president of the municipality Christian Däpp last Friday. It proves: The Aeschi school is built from Swiss wood. The showcase project was already put into operation by the students in Aeschi last spring.

Wood construction is gaining significant market share throughout Switzerland. There are good reasons for this: Wood is by far the most climate-friendly building material. The naturally renewable raw material requires only solar energy and water for its production. Harvesting and processing require very little energy, and the material also stores the greenhouse gas CO₂. The wood used in the Aeschi school building permanently stores 652 tons of CO₂.

Originally planned in steel and concrete

The old school building in Aeschi bei Spiez, built in 1909, has reached the limits of its capacity. A new three-story building in timber construction is now extending the school building. Originally, a project made of reinforced concrete was planned. Thanks to the persuasion of various stakeholders, a modern wooden building - with wood from the surrounding community forests - now stands next to the old school building.

Own wood in public buildings

The new public procurement law (BöB) has been in force since January 1, 2021. Here, a paradigm shift towards more sustainability and quality competition is taking place. Procuring good quality is an advantage for everyone. After all, excessive price weighting has inhibited suppliers from offering innovative solutions. New award criteria such as "innovation" make it possible to reward good solutions.

BöB is therefore an opportunity for even more timber construction projects and innovative technologies. Let's tackle them together! However, BöB also has its pitfalls. For example, in the procurement of regional wood. Public construction projects that exceed the threshold value of 9.575 million Swiss francs must be put out to public tender. The same applies to the services of the main construction trade (e.g. carpentry work) or individual supplies (e.g. cutting of logs) if they exceed the threshold of 500,000 Swiss francs or 250,000 Swiss francs. New construction projects such as the Aeschi school building must therefore be put out to public tender. According to the principle of non-discrimination, no requirement may be imposed with regard to the origin of the material. It is not permissible to demand Swiss wood or wood from a certain area around the building.

However, there are ways in which wood from the surrounding area can be used despite public tendering: The provision of the wood by the building owner himself, the so-called in-house procurement, is one of them. Communities such as Aeschi, which have large forests of their own, are allowed to provide the raw material and define this in the tender. It is also particularly interesting that the degree of processing of the products is optional. This means that whole logs, sawn timber or glued products can be provided.

Two options for in-house procurement

Direkte Verwendung von Holz aus den eigenen Wäldern	Indirekte Verwendung von Holz aus den eigenen Wäldern
Bei der direkten Nutzung ist sichergestellt, dass das in den eigenen Wäldern geschlagene Holz auch tatsächlich für ein bestimmtes Bauprojekt genutzt wird. Jeder gefällte Baum wird für eine bestimmte Verwendung geplant und seine Rückverfolgbarkeit ist jederzeit gewährleistet.	Bei der indirekten Nutzung wird gleich viel Holz geschlagen, wie für ein bestimmtes Bauprojekt verwendet wird. Dieses Prinzip ermöglicht einem Waldbesitzer, seine eigenen Ressourcen zu nutzen. Das Holz wird nicht direkt für den bestimmten Bau verwendet, aber die gleichen Holzmengen werden auf dem Schweizer Markt gehandelt.

Early decision necessary

For the planning process, it is crucial that the decision to use regional wood is made early. Timber can only be cut in winter, so planners and builders need to know as early as fall which trees will be needed for the project. At least a rough planning of the cross-sections, including reserves and the approximate proportion of hardwood and softwood, is essential at this stage.

Clever planning

The extension building cleverly combines the solid wood and frame construction methods: All load-bearing walls and the floor slabs are made of glulam in solid wood construction. The interior walls are non-load-bearing frame structures. Largely knot-free fir boards were used for the facades. A dry-bonded fill (Köhnke grit) was used as sound insulation. Another exciting aspect of this project was the fire protection solutions: The vertical escape routes are designed as an encapsulated wooden structure.

The school building has the special feature that an increase in height has already been planned and can be easily carried out because all components are dimensioned in such a way that the school building can be increased by one storey at a later date. For this purpose, the forces are largely transferred via wooden columns that run the entire height of the building and are clamped at the bottom. In addition, the interior walls are non-load-bearing and thus allow maximum flexibility of use.