The walls of PH-Z2 – a project for Zeche Zollverein in Essen, Germany – consist of heavy bales of used, pressed packaging paper. PH-Z2 is part of ‘Mobile Working Spaces’, an initiative organized by local authorities. Ben and Daniel Dratz of Dratz&Dratz Architekten reused this material to build a temporary event hall with 185 m2 of multifunctional space and a roof that doubles as a terrace. Removing the building at the end of 2011 will be easy: the paper is part of a recycling chain and will go on to serve other purposes.

How did the use of paper as a building material come to mind?
Daniel Dratz: Rather unexpectedly, we passed by a recycling station and saw these bales of used paper. We were fascinated by the structural variety and by the fragments of compressed information – like traces of society. Later we discovered that these bales could be layered and stacked to form monolithic walls, and we recognized the potential for architectural
projects.

How did you handle the material in terms of construction and insulation?
Ben Dratz: Since we had no valid precedents, we had to rely on evidence gathered during our own experiments and research. We tested the paper’s reaction to humidity, as well as its statics and its deformation under certain pressures. We concluded that very compactly pressed bales provide good heat and sound insulation, and that the material is hardly flammable. We used a polysiloxane coating to keep the walls dry.

What other materials did you use?
Daniel Dratz: Our concept called for only ecological materials. The roof is a conventional timber construction, and the windows are recycled plastic sheets that open onto a view of a birch forest – a poetic, indirect allegory of the origins of the cellulose fibres used to make paper.

What about the patent you applied for?
Ben Dratz: Our long-term plan is to sell bales of paper as a construction material. Of course, the precommercial development of products is very difficult for us architects. Nevertheless, we believe in this material: it’s cheap and eco-friendly, and it’s given us new ideas for future architecture.

Interview: Sandra Hofmeister