A school made of regional wood

29.06.2022

Line

Over the next ten years, school buildings will be needed to accommodate about 3,000 additional classes. Preferably these will be built with regional wood. A good example is currently under construction in Prêles, above Lake Biel.

The number of births is increasing, so the school children need more space. In the next ten years, classrooms for about 3,000 additional classrooms will be needed, writes the NZZ on Sunday, June 26, 2022. If these 3000 classrooms were built in new buildings, this would mean a need for about 200 new secondary and elementary school and 250 new kindergartens. In theory, almost one new school unit per week would have to be created.


Ideally in wooden buildings  

It makes sense to realize the enormous need for new classrooms in wooden constructions. Wooden constructions are quickly completed thanks to short assembly times. The components can be prefabricated in the factory to the millimeter, stored in a weatherproof location and then transported to the construction site where they are quickly assembled. Cost-effectiveness is also guaranteed: Thanks to lower heating, maintenance and demolition costs, timber construction is cheaper than solid construction over the entire life cycle of a building, despite the sometimes higher construction and planning costs. 


Wooden buildings as a CO-sink 

Wooden buildings have a justified reputation for being climate-friendly, because wood is a naturally renewable raw material that requires only solar energy and water for its manufacture. Through photosynthesis, trees extract CO2 from the atmosphere, transform it and store it. Wooden constructions thus become CO2 sinks, which are called «NET negative emission technology», and which we will not be able to do without in the future according to the Federal Office for the Environment (Link).


Harvesting and processing are also energy-efficient. A wooden building, made with wood from the nearest environment, is of course particularly environmentally friendly. The new school in Prêles is a good example. The trees come from the surrounding forests of the Plateau de Diesse, south of the Chasseral, and were transported only a few kilometers for processing. This greatly minimizes the grey energy contained in the construction elements. 


After the harvest 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 then delivered to JPF-Ducret for gluing. A part of the wood was also transported to Schilliger Holz AG for the manufacture of tri-ply panels, the only Swiss company currently manufacturing this type of product.


The way to your own wood  

The use of regional timber is not a problem for privately financed construction projects. For large public construction projects, the situation is a little more complicated: according to the Federal Act on Public Procurement (PPA), different types of procedures are prescribed depending on the value of the contract. Construction projects exceeding the threshold value of CHF 9.575 million must be put out to public tender. The same applies to services in the main construction sector (e.g. carpentry work) or certain supplies (e.g. sawing of logs) if they exceed the threshold value of CHF 500,000 or CHF 250,000. Construction projects for new buildings, such as schools, must therefore generally be put out to tender. According to the principle of non-discrimination of the PPA, no requirements can be made regarding the origin of the materials. Unfortunately, it is not possible to demand only regional wood. It is also not allowed to require that the wood comes from a certain perimeter around the construction, which would obviously be very sensible from an ecological point of view. And so the contractor who gets the contract can decide where the wood they want to use comes from. Often it's a cheap alternative that's chosen, and most of the time it's not the regional alternative.

There are, however, possibilities to use wood from the surrounding area despite the tender: The provision of wood by the client himself, the so-called in-house supply, is one such possibility. Municipalities, such as the mixed municipality of the Plateau de Diesse, which have abundant raw materials at their disposal, can make them available and thus define this in the tender. It is also particularly interesting that the degree of processing of the products is free. This means that whole logs, sawn timber or even glued products can be made available. 


Two possibilities for in-house procurement 

There are basically two types of in-house procurement. Direct harvesting guarantees that the wood felled in the company's own forests is actually used for a specific construction project. Each tree felled is planned for a specific use and traceability is guaranteed at all times. 


Indirect harvesting consists of cutting as much wood as is used for a given construction project. This principle allows a forest owner to exploit its own resources. The wood is not used directly for the construction in question, but the same quantities of wood are traded on the Swiss market.


Direct use for the school in Prêles

For the school in Prêles, the choice was made to use wood directly from the building. The spruce trees that once grew on the Diesse plateau are now the pillars, beams, walls and ceilings of the new school. Spruce grows quickly and has good timber properties for building construction. Beech wood is also used in some places. For example, as a support for the 13-ton staircase in the middle of the school. It was delivered to the site as a prefabricated concrete element and mounted on the beech beams.

Betontreppe auf Fagusträger

For the planning process, it is essential that the decision to use one's own wood directly is made early on. Timber can only be cut in the winter, so the planner and owner must know in the fall which trees will be used for the project. A rough planning of the cross-sections, including reserves and the approximate proportion of hardwoods and softwoods, is essential at this time.


A good indoor climate

The new school skilfully combines solid wood and frame construction: All load-bearing walls and floors are constructed of solid wood and glulam. The interior walls are non-load-bearing frame construction. The warm surfaces of the wooden walls and ceilings, as well as the permanent exchange of the wood with the air humidity, provide a good indoor climate. Well insulated walls are important: the smaller the difference between the surface temperature of the walls, floors and ceilings and the air temperature, the better the room climate. This is why we feel comfortable in wooden buildings with good thermal insulation, even when the ambient temperature is slightly lower. This allows buildings to be operated more energy-efficiently. In addition, wood has a higher surface temperature than concrete, steel or glass, which further increases the feeling of well-being.


Film project 

The construction work is currently underway and next summer the students of the surrounding communities will take possession of their new school. Until then, we are accompanying the entire construction process with a film crew.

Dreharbeiten

Beteiligte Schulhaus Prêles

Architektur: Chapuis Architectes SA http://www.chappuisarchitectes.ch/ 

Holzbauingenieur: Timbatec AG in Delémont https://www.timbatec.com/en/index.php

Holzbau: Charpentes VIAL SA https://www.vialcharpentes.ch/fr/ 

Brettsperrholz: Schilliger Holz AG https://www.schilliger.ch/ 

Verleimung von Brettschichtholz: JPF-Ducret in Orges 

Sägerei: Despond SA Scierie, Bulles

 
 
 

Switzerland:

Thun Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Niesenstrasse 1, 3600 Thun

Tel: +41 58 255 15 10

thun@timbatec.ch


Zürich Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Ausstellungsstrasse 36, 8005 Zürich

Tel: +41 58 255 15 20

zuerich@timbatec.ch


Delémont Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Avenue de la Gare 49, 2800 Delémont 

+41 58 255 15 40 

delemont@timbatec.ch


Bern Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Falkenplatz 1, 3012 Bern

Tel: +41 58 255 15 30

bern@timbatec.ch

Austria:

Headquarters Vienna (A) 

Timbatec Timber Construction Engineers GmbH
Im Werd 6/31a, 1020 Wien 
Tel: +43 720 2733 01

wien@timbatec.at


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