Open day - a huge success



Full house at the open day. Over 180 people wanted to see and feel the basement made of wood. The BMW15 apartment building in Thun is an innovative showcase project: it stands on the first basement made of wood in Switzerland, manages without heating and was built entirely without concrete.

The interest in the showcase project was enormous: On Saturday 13 November 2021, over 180 people visited Stefan Zöllig's new building. We are pleased about the large number of visitors and the exciting coverage in the daily newspapers or 20 Minuten online.  

The visitors could see it for themselves: Comfortable temperatures prevail in the apartments - even without heating. The fact that modern houses can manage without any heating at all is proven in Thun. There are many sources of heat in buildings, such as kitchen appliances and computers. People also radiate heat constantly. If, in addition, the sun's rays are ideally used and the house is well insulated, there is no need for heating today if the design is good.

Surface temperature advantage 

Well-insulated walls are important. The smaller the difference between the surface temperature of the walls, floors and ceilings and the air temperature, the more comfortable it is in a room. That's why we feel comfortable in wooden buildings with good thermal insulation - even when the room temperature is somewhat lower. This allows buildings to be more energy-efficient. In addition, wood has a perceived higher surface temperature than concrete, steel or glass, which further increases the sense of well-being.

BMW15 Aussen und Innenansicht

From the outside and inside: Wood remains visible and gives the building a pleasant atmosphere. 

Enabling efficient night cooling 

Due to global warming, there will be more and warmer heat days in the future with temperatures above 30 degrees Celsius. Thermal insulation in summer is therefore becoming increasingly important. In order for us to feel comfortable even on hot summer days, buildings must be able to cool down during the night. Windows with adequate weather and burglar protection and insect screens are important for this. Exterior shading and appropriate window size are equally important. 

Mass equals stupidity 

For a long time, it was believed that summer thermal protection could only be achieved by installing a lot of mass. This is wrong. Old castles with their meter-thick walls may remain cool in summer. But this is due in particular to the small windows. Modern architecture often has large window areas. Once heated up, too much thermal mass can become a heat trap, especially in inner-city locations where buildings cannot cool down sufficiently at night. Important influencing factors for good summer thermal insulation are adequate window areas, good solar shading and efficient night cooling.

BMW15: Keller aus Holz

What seemed impossible for a long time is now a reality: Thun is home to the first apartment building with a basement made entirely of wood.

Houses without heating and without air conditioning make an important contribution to climate protection. An even greater potential for energy saving lies in the choice of building materials. Wood is already widely used in building construction. The next step is to dispense with climate-damaging building materials such as steel and concrete - including in basements and floor slabs. In order for basements to be mass-produced from wood in the future, a number of research questions need to be clarified. A research project of the Bern University of Applied Sciences together with Timbatec, TS3 and other business partners is currently addressing these questions. A start-up is to be founded from the group of research partners, which will be operationally active from 2023.

BMW15: Übergabe Zertifikat

The certificates prove the use of Swiss wood and the storage of a total of 222 tons of CO₂: Thomas Lüthi from the Initiative Holz BE and Stefan Zöllig handing over the certificate. 


A lot of wood is visible on the outside and inside. The TS3 technology allows for a column-and-panel construction method. The TS3 joints remain visible in this project.  

The creation

In the video you can see how the building Thun was created.



Thun Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Niesenstrasse 1, 3600 Thun

Tel: +41 58 255 15 10

Zürich Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Ausstellungsstrasse 36, 8005 Zürich

Tel: +41 58 255 15 20

Delémont Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Avenue de la Gare 49, 2800 Delémont 

+41 58 255 15 40

Bern Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Falkenplatz 1, 3012 Bern

Tel: +41 58 255 15 30


Headquarters Vienna (A) 

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


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