School from regional wood

^© Pictures: Da Campo Luca, Photographe, Lausanne

The number of births is rising, and the schoolchildren need more space. In the next ten years, school space will be needed for around 3000 additional classes, writes the NZZ am Sonntag on June 26, 2022. all these 3000 additional rooms in new buildings, this would result in a demand for 200 new upper and primary school buildings and 250 new kindergartens. kindergartens. In theory, almost one new school unit would have to be created per week. per week.

Ideally in wooden buildings
It makes sense to realize this huge demand for new for new classrooms in wooden buildings. Thanks to short assembly times, wooden quickly thanks to short assembly times. The components can be prefabricated prefabricated in the factory, transported to the construction site, and quickly assembled there quickly. Economic efficiency is also guaranteed: Thanks to lower heating, maintenance and dismantling costs, timber buildings are usually cheaper over the entire life cycle of a building. costs over the entire life cycle of a building than solid structures, despite the the sometimes higher construction and planning costs.

Wooden buildings as CO₂ sinks
Wooden buildings are climate-friendly, as wood is a naturally renewable raw material that requires only solar energy and water for its solar energy and water for its production. With photosynthesis, trees remove CO₂ from the atmosphere, convert it and store the carbon in the wood. In this way wooden buildings become CO₂ sinks, to the so-called negative emission technology NET, which, according to the Federal Office for the Environment, we will no longer be able to do without in the future. The Federal Office for the Environment recently published an exciting brochure on this topic (link).

Harvesting and processing are also energy-saving. A wooden building that is erected with wood from the nearest surrounding is, of course, particularly environmentally friendly. The new school in Prêles is a good example of this. The trees come from the surrounding forests of the Plateau de Diesse, south of the Chasseral, and were transported for processing transported only a few kilometers for processing. This means that the elements is greatly minimized.

After harvesting in the winter of 2020/21, the forestry companies delivered the wood to the company Despond SA in Bulles for the production of lamellas, which were subsequently delivered to JPF-Ducret for gluing. Some of the wood was also transported to Schilliger Holz AG for the production of three-layer boards. Schilliger Holz AG, the only Swiss company currently producing this type of product. type of products currently manufactures.

The way to own wood
The use of wood from the region is possible without any problems in privately financed construction projects. For larger, public construction projects, the situation is somewhat more complicated. (BöB), different types of procedures are prescribed depending on the value of the contract. different types of procedures are prescribed depending on the value of the contract. Construction projects that exceed the threshold of CHF 9.575 million must be put out to public tender. The same applies to services of the main construction trade (e.g. carpentry work) or individual deliveries (e.g. cutting of logs), if they exceed the threshold value of threshold value of 500,000 Swiss francs or 250,000 Swiss francs respectively. New construction projects, such as school buildings, must therefore usually be put out to tender. be put out to tender. According to the principle of non-discrimination in BöB, no requirement may be made with regard to the the origin of the material. Unfortunately, it is not permissible to is therefore unfortunately not permissible. It is also not allowed to demand that the wood comes from a certain area around the building, which would of course make which would of course make a lot of sense from an ecological point of view. And so the contractor who wins the The contractor who is awarded the contract is free to decide where the wood he wants to use comes from. Often a cheap solution is chosen, and this is usually not the regional alternative.

However, there are ways in which, despite tender, wood from the surrounding area can be used: The provision The provision of the wood by the building owners themselves, the so-called in-house procurement, is one of them. Municipalities, such as the mixed municipality of Plateau de Diesse, which have have their own raw materials may provide them and define this in the tender. define this in the tender. It is also particularly interesting that the degree of processing of the products is optional. This means that whole This means that whole logs, sawn timber or glued products can be provided.

Two options for in-house procurement
There are basically two different types of in-house procurement. In the case of direct use, it is ensured that the wood harvested in the company's own forests is actually used for a specific construction project. specific construction project. Every tree that is felled is planned for a specific use and traceability is guaranteed at all times.

With indirect use, the same amount of Timber is cut as is used for a specific construction project. This principle allows a forest owner to use his own resources. The wood is not used directly for the specific construction, but the same quantities of wood are traded on the Swiss market.

Direct use for the school building in Prêles
For the school in Prêles, the direct use of the own use of its own wood was chosen. The spruces that once grew on the Plateau de Diesse grew are now the supports, beams, walls and ceilings of the new school. Spruce wood grows quickly and has good wood properties for the construction of buildings. At beech wood is also used in selected places. For example, as a support for the 13-ton staircase in the middle of the school building. It was delivered to the site as a prefabricated concrete delivered to the construction site and mounted on the beech girders.

For the planning process is crucial, that the decision for the direct use of one's own wood is made at an early stage. is made early on. Timber can only be felled in winter, so planners and builders must therefore need to know in the fall which trees are needed for the project. will be needed. At least a rough planning of the cross sections, including reserves and the approximate proportion of hardwood and softwood, is essential at this stage. indispensable.

A good indoor climate
The new school cleverly combines the wood solid and the frame construction method cleverly: All floor slabs and part of the and part of the interior walls for the building's bracing are made of solid timber glulam. The remaining interior walls are non-load-bearing frame buildings. The warm surfaces of wooden walls and ceilings, as well as the constant exchange of the wood with the air humidity result in a good indoor indoor climate. Well insulated walls are important: because, the smaller the difference between the surface temperature of the walls, floors and ceilings and the air temperature air temperature is, the more comfortable it is in a room. That is why we feel feel comfortable in wooden buildings with good thermal insulation - even at somewhat lower room temperature. In this way, buildings can be operated in a more energy-efficient manner. In addition, wood has wood has a perceived higher surface temperature than concrete, steel, or glass, which additionally which additionally increases the sense of well-being.

Film project
This project impressively demonstrates that educational buildings today can be constructed in wood without compromise. "From tree to school building" is the working title of a report on this project. The film shows the process from the selection of the trees in the community forest, the felling and transport, the industrial processing and fabrication, the timber construction work on the building site to the construction of the finished building.