Description

Two camps have formed in the search for approaches to reducing the immense carbon emissions in the building sector: high-tech and low-tech. Sensible building technology can help reduce the energy consumption of buildings, but the technology itself is not free of grey energy. Might not a more radical renunciation of building technology be a more resolute approach?

The “2226” office building by Baumschlager Eberle Architekten in Emmenbrücke, Switzerland, demonstrates once again what such an approach can look like. Its name derives from the constant “comfortable temperature” of between 22 and 26 degrees. With no heating, cooling or mechanical ventilation, the new five-storey building has been billed as “miracle of building energy management”.

The architects see their concept as a manifesto for sustainable building. Thick, solid masonry walls, as seen in traditional Engadine houses, provide thermal mass, and a sensor-controlled ventilation concept ensures that the indoor climate remains pleasant. Baumschlager Eberle Architekten demonstrated that this concept delivers on this promise in their own company headquarters in Lustenau, Austria, built in 2013. In the two-year development phase, the architects modelled all the parameters in advance, experimenting with wall thicknesses and room heights. The actual data collected over the last few years lies within the envisaged target temperature range, thus confirming their model. And the users were also convinced: 95% found the indoor temperature pleasant, even on the coldest day of the year.

The new building in Emmenbrücke encompasses a total of 2815 m² of floor space and replaces an old factory building. The monolithic structure adopts its predecessor’s basic urban arrangement, building height and hipped roof form. The double-shell wall construction comprises two layers of 38 cm thick, loadbearing and heat insulating brickwork with 15 mm of lime plaster on the inside and outside. Its light colour reduces heat gain in summer. The solid building shell absorbs heat during the day, releasing it with a time lag to the interior at night.

The floor plan is kept open with a central circulation core with toilets and ancillary spaces in the centre. The internal loadbearing elements are likewise constructed as brick masonry. The combination of waste heat from people, technical equipment and lighting, and winter solar gain provides sufficient warmth to heat the building. Sensors on each floor measure temperature, carbon dioxide content and relative humidity and compare these against measurements from a weather station on the roof. A software system then regulates the indoor air quality by operating ventilation flaps integrated into the deep-set frames of the fixed-glazed windows, thus ensuring a pleasant room temperature and air quality. The building’s users can override the automatic system using the software, though this is not always advisable at extremely high or low temperatures, as it allows too much warm or cold air to flow in.

For the ventilation concept to work, a sufficiently large volume of air is required, provided by a room height of 3.40 metres on the main floors and 4.50 metres on the ground floor. The ratio of openings to solid external wall surface is comparatively low at only 18%, though this is 2% more than the prototype in Lustenau, Austria. Setting the windows close to the interior creates deep reveals that function as natural shading and reduce heat gain in the interior. Light-coloured floors and walls also ensure the interiors are bright and light so that less artificial lighting is needed. The regular rhythm of the openings helps ensure uniform light levels and cross-ventilation, but ultimately it is as much a stylistic and cost-saving decision.

Alongside the durability of the building’s structure, its neutral functional declaration also contributes to the long-term sustainability of the 2226 building. While the prototype in Lustenau contains a mix of offices, flats and a fitness studio, the 2226 in Emmenbrücke houses, among other uses, an educational institution for 650 pupils.

Originally published in Bauwelt 24.2019, pp. 62-65, abridged and edited for Building Types online, translated by Julian Reisenberger

---