Unbeknown to many, cork is something of a dark horse when it comes to the environment—a model of a sustainable industry and building material. By its very nature, cork is both recyclable and renewable, as it is the only tree that regenerates its bark, while harvesting that bark causes the tree no harm.
Cork has been sneaking its way into our buildings for many years now; due to its hard-wearing properties it can be found, for example, in the checkerboard flooring of the Library of Congress. Even NASA has been wise to cork's light weight and insulation capacity, using it as an insulator for their space shuttles.
Only recently have we seen a growing curiosity over cork as an external cladding material for buildings. Despite what many assume, cork is extremely waterproof (why else would we trust it as a stopper for our precious wine), resistant to abrasion, and acts as a fire retardant and an acoustic insulator. Its also has desirable aesthetic qualities, giving buildings mottled earthy tones and natural patterning.
Portugal is the largest producer of cork in the world; it is here where the material begins its life as the bark of cork oak trees in large agricultural forests called montados. The process by which the cork is handled couldn’t be much more sustainable: it is harvested by stripping the outer layer of skin off the tree with a small hatchet that then regrows in time for the next harvest. In the factory, the cork is shredded and compressed at high temperatures, causing it to expand and the sap to melt to form a glue that binds it all together. Once cooled, it can be cut to measure ready to be put up as cladding. None of the harvested bark goes to waste in the process apart from the dust produced along the way. And that’s it—no added ingredients!
In Portugal the regulations for the cork industry are extremely tight, ensuring sustainable production, and the trained workers are paid a good living wage. By law, cork oaks cannot be harvested until the tree is at least 25 years old and even then, it can only take place every 9 years. The trees also require no pesticides, irrigation or pruning. The stripped trees absorb vast amounts of carbon dioxide and release more oxygen, so Portugal's montados are often referred to as the "lungs" of the environment. According to the World Wildlife Fund, they also play an important role in protecting biodiversity in the forest:
Cork oak forests support one of the highest levels of biodiversity among forest habitats, as well as the highest diversity of plants found anywhere in the world.
– World Wildlife Fund
An increase in demand for cork would benefit the environment, as the industry would need to plant more trees that encourage these habitats to grow and consume more carbon dioxide.
The adaptability of cork as a material has meant many buildings are beginning to use it for both external and internal uses. When used internally, in the case of the Heart Clinic by Dost, the cork regulates humidity, absorbs odors and provides comfortable sound reverberation, perfect for a clinical environment that aesthetically benefits from an organic, warm atmosphere. As cladding, the impermeable cork protects the building against the elements for a significantly carbon negative material.
Below are 14 examples to offer inspiration for how cork can be integrated into a building: