In an illustration of how something considered a throwaway item can become a paragon of sustainability, cork has emerged as a building material with impeccable green credentials. Designers and architects, swayed by its aesthetic qualities, use it increasingly in construction and it can be found in some very unlikely places.
Portugal, the largest producer of cork in the world, has rigid regulations to ensure continuing sustainable production. Cork is harvested by stripping the outer layer off cork oak trees at which stage regrowth begins. The trees must be 25 years old before they are harvested and then left to regrow for nine years before they can be harvested again.
The ecological boxes ticked by this material are endless. As alluded to above, it is natural and renewable and also recyclable, biodegradable and entirely environmentally friendly. The trees require no pesticides, irrigation or pruning. In Portugal, their carbon absorption attributes – they take in huge amounts of carbon dioxide and emit oxygen – accords them the description as the “lungs of the environment”.
Cork as a building material can incorporate many characteristics which other materials can only provide in a discrete way. As proven through the ages through stoppering wine bottles, cork is waterproof. It is light in weight, breathable, absorbs sound and is as effective an insulator as can be found.
These qualities also aid the process of turning it into such a versatile building material. The stripped cork is shredded and compressed at high heat. It expands until the sap dissolves into a form of glue which binds the cork together. It is then ready to be cut into squares for use in construction.
Viewed from a distance, cork used as cladding has an abrasive appearance which upon closer inspection acquires a veneer of warmth. This is not just a veneer – the qualities listed above are precisely those needed to make houses less draughty and more conducive to heat retention.
Visionary architects have used cork throughout history: the floor of the US Library of Congress was fashioned from cork in the 18th century and it was used in some of the most celebrated designs of Frank Lloyd Wright. Cork has even broken free of earth’s shackles when used as insulation by NASA for their space shuttles.
The development of cork as material for external building use has given it a new lease of life now that so many wine producers use plastic or metal screw caps. With trees which live for up to 300 years and all those inherent eco-friendly properties, it is destined to be a green favourite.