Authors: Professor Arch. Walter Unterrainer
Wood is considered a sustainable building material, for good reasons: it grows in many regions and it is renewable, wooden buildings store CO2 which was sequestrated while the trees were growing and work like Carbon sinks. Many old buildings worldwide document that wood is a durable building material and it has fantastic material properties, like a better relationship between structural performances and own weight compared to metals or positive thermal and sensual qualities. Architects or students when asked about the ´green content´ in their projects, often answer ´it is built in wood´. Unfortunately the truth is more complex. To express it pointedly: it is far easier and more common to design and construct an unsustainable building in wood than a sustainable! This depends on decisions on many different scales and layers, from very large scale to micro-detail. At least five individual conditions can be summarized which decide whether a wooden building is sustainable or it only pretends to be: • The origin of wood: Where and how is it harvested and how sustainable is the forestry • The place of manufacturing wooden elements and industrial semi-products • The embodied energy for drying, processing and manufacturing • What glues, paints, impregnations, foams etc. were applied, which turn the original natural building material into a problematic, sometimes even toxic substance? • How is the building detailed, executed, kept dry during the building process to make it a long life and low maintenance building? Wood can be a fantastic building material. Based on direct and on-site investigation and analysis of exemplary buildings in different regions and on four decades of experience by the author in building with wood, the paper elaborates and visualizes the difference between long-lasting wooden architecture with high environmental benefits and greenwashing, short-life and high maintenance projects. Poor results support prejudices and undermine the potentials of wooden architecture due to negative public opinion.
Keywords: wooden architecture; sustainable construction; lowmaintenance details; embodied energy; ageing of wood