Is Cork the Most Sustainable Building Material?

If you ever opened a bottle of wine, you have seen the main product made from the cork oak tree. Billions of corks are made every year, but only a percentage of the harvest is used. The remainder is ground up and used in bulletin boards, flotation devices, boat decks, sports equipment and building materials.

Its qualities make it versatile, uniquely beautiful and energy efficient for homes and businesses. Those same qualities and the way it is harvested make it a highly sustainable building material.

Where does cork come from?

The cork oak tree is native to the Mediterranean regions of southern Europe and northern Africa. It is the only tree that can have the bark removed without killing it. This allows it to be repeatedly harvested.

The first harvest is when a tree is about 20 years old. In mid-summer, the bark is removed from the trunk and main branches with special axes of different sizes. It grows back and can be harvested again in about nine years. The life expectancy of a cork oak tree is over 200 years, so one tree can be harvested about sixteen times. The cork pieces are weathered outside for six months, which improves its quality. The repeat harvest also improves the cork while making it a sustainable product.

Cork harvesting

Photo: Cazalla Montijano, Juan Carlos

Cork has been harvested by hand for 2000 years but only for commercial purposes since the early 1700s. Machinery is never used. It’s all done by hand, and the skills are passed down through the generations. Harvest of the trees and manufacture of corks creates tens of thousands of jobs. Also, the axes are made locally, which creates even more jobs.

How cork is used

As a building material, cork is in high demand now. It is used for flooring, rigid insulation, exterior finish, floor underlayment, acoustic wall coverings and countertops. It has air pockets that make it resilient for floors. There is a little give, so your feet, legs and back are not stressed the way they are on concrete or tile.

Those air pockets also make cork good for insulating. Air keeps heat and cold from moving between indoors and outdoors. Rigid cork insulation has been used in Europe for decades, but it is a recent introduction to North America. Its acoustic qualities also come from the air pockets.

Cork is naturally anti-microbial, making it a good choice for bathrooms and kitchens. It is impermeable, yet it breathes, so it resists mold and mildew. At the same time, it resists fire. It is said that the tree evolved this bark to resist forest fires.

Cork is non-toxic and does not off-gas VOCs. It gives a warm, cozy and organic feel to an interior space. Each piece of bark is unique in texture, grain and color, for a one of a kind look. Cork satisfied LEED credits for being renewable, recycled and having low emissions.

Because corks as bottle stoppers are being replaced with plastic corks or screw tops, the cork industry is slowing down. You can help keep this sustainable industry alive and keep thousands of people working by buying cork products. There are many uses for it around the home, and now furniture designers are playing with it, since it’s so lightweight.

Cork oak is a protected species

The cork oak tree is so important to the Mediterranean economy that it is federally protected. It’s illegal to cut them down. Farmers even have to ask permission to remove trees that are ill or beyond their use. There are roughly 5.5 million acres of cork oak planted. Sixty percent of production is in Portugal. Cork forests are FSC Certified.

Cork oak trees

The harvest of cork is sustainable, but there is always the argument that shipping it from Europe to North America is not. Perhaps its low embodied energy and energy efficiency as a building material offsets that.

Cork in the United States?

Cork needs little water, lots of sun and a sandy soil to flourish. The southern and western US have good conditions for growing cork, which would reduce the environmental effects of transporting it. Imagine something as sustainable as cork being locally grown! That would probably have a negative carbon footprint.

Cork seems like the perfect building material. It’s not just for wine and bulletin boards anymore!

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