Got Cork?

With a variety of approaches and opinions on how buildings can be well insulated, builders are increasingly looking for alternatives to heat-insulating plastics such as EPS (expanded polystyrene), which, when installed in a thermal insulation composite system (EIFS), is not ideal in regard to fire protection. Environmental concerns are also important, and manufacturers have responded with some sustainably produced and recyclable insulating materials. More and more, architects specify alternative ecological products because they know natural materials help in creating healthy and pleasing residential environments.

Andreas Reeg and Marc Dufour-Feronce from Berlin's rundzwei Architekten took an interesting approach in their design of a house in Berlin-Staaken. The young firm placed a particular importance on the choice of materials relative to the house's plan. The lowest level, still largely below the ground level, is defined by walls of rammed concrete: The centuries-old building material is traditionally introduced layer by layer and compacted by hand. The result is a rough surface that gives the impression of a cave as one descends within the house. Counteracting this are large glass surfaces placed above the concrete.

Capping the walls of rammed concrete and glass is a pure wood construction, with walls and roof surfaces covered on the outside with cork panels. The material — cork granulate, a byproduct of bottled cork production — comes from Portugal. The facade panels are made by adding heat and pressure, a process that releases the resins in the cork and binds the granules together. The cork panels are therefore naturally resistant to weather and mold without any additives or chemicals. Furthermore, cork has very good insulating properties and it also — ​​a plus for the builders, who actually brought the material to the architects — absorbs the dripping noise of rain.

The use of natural building materials runs throughout the project. During construction, no glue or polyurethane foam was used. In addition to the insulating cork boards, wood fiber and cellulose insulation was used. Moisture absorbing materials, such as wood and gypsum-fiber surfaces with diffusion-free coatings, create a natural room climate. The KfW 55 house does not need a ventilation system. Thanks to a stratified storage system, which is supported by solar panels integrated in the roof, the heat supply of the house is almost self-sufficient.

A version of this article originally appeared as "Korkenzieherhaus" on German-Architects.