Net-zero residence with cork façade.
Courtesy Dwell Development Net-zero residence with cork façade.

A decade ago, cork was in crisis. Though the material had been used in wine bottles for centuries, the Portuguese cork industry—which supplies most of its raw material for use in wine bottles—was facing stiff competition from manufacturers of plastic and metal screw-caps, which were gaining in popularity due to increasing instances of “corked” bottles.

The reduced demand for cork led to an industry-wide recalibration. "What we have witnessed in the last 10 to12 years in the cork industry is a real revolution,” said Antonio Rios de Amorim, president of the leading cork producer, Corticeira Amorim, in a July 2017 Forbes interview. Corticeira Amorim and other Portuguese cork suppliers took a hard look at both quality control and market factors and decided to make significant changes. “The cork industry really questioned itself,” Rios de Amorim said. “We started to innovate, started to introduce new technologies.”

And the result? Today, cork has rebounded thanks to three critical factors: higher quality processed material, increased public awareness about its environmental performance, and market diversification to sectors including architecture and design.

Cork’s use in buildings is nothing new. In fact, ancient Egyptians, Greeks, and Romans used cork for various functions, including building insulation, ship flotation, and footwear. Although the primary market for the material today remains bottle stoppers—which comprise some 60 percent of Corticeira Amorim’s exports—architectural applications are once more on the rise.

Perhaps the most familiar building application today is flooring. Cork has been widely used as a resilient floor surface material that provides cushion and noise absorption. It is typically offered in tile and plank formats and applied as floor underlayment. Though modern cork flooring was first installed more than a century ago, manufacturers, such as Boulder, Colo.–based Sustainable Materials, are reinvigorating the cork flooring market. But the company is also going vertical. By tightly packing recycled wine corks with their tops at a flush height, the manufacturer's Versacork Mosaic material resembles mosaic ceramic tiles. The prefinished version is waterproof and appropriate for wet bathroom or kitchen environments, like ceramics, but with more give and sound absorption.

Courtesy Sustainable Materials

Increasingly, manufacturers and specifiers are embracing cork as a vertical and exterior surfacing option. Sustainable Materials' portfolio of wall finishes also includes cork bricks, patterned tiles, and Organic Blocks. The latter features a compression-molded cork that assumes an incredibly smooth appearance and comes in many multidimensional shapes, such as hexagons, teardrops, strips, or pyramids—each of which enables intricate repeating surface geometries.

Netherlands-based Pro Suber sells a cork façade panels made of heated agglomerated cork granules bound together with the natural resin in the material. Three-inch-thick sheets provide protective cladding that is thermally insulating, noise reducing, and—due to the high density of the material—water resistant.

Porto, Portugal–based ATKA Arquitectos specified a cork façade for a local residential renovation, primarily for acoustic reasons. “We used expanded corkboard to affirm this protruding volume, and suppress noise from a school playground nearby," the architects said in a Dezeen interview. "Cork is entirely natural, and offers an alternative to more conventional forms of insulation, with a good acoustic and thermal performance.” Seattle-based Dwell Development designed a house in with untreated cork cladding to make what the firm declares to be the “first net-zero speculative house in Seattle.” The imported façade material was particularly attractive because “cork is also one of the only materials on earth that can be submerged in liquid for centuries without rotting, making it virtually immune to the Pacific Northwest’s damp climate,” according to the developers.

Panels and strips are not the only formats for cork façades. Albacete, Spain–based coating company DecoProyec makes Projected Cork, a spray-finish material composed of fine cork granules and vegetable resin in a water base. When applied to building envelopes, the resulting stucco-like finish is waterproof and well-insulating, yet also breathable and resilient. Projected Cork resists cracking and splitting, and is capable of extending up to 33 percent beyond its original surface area.

Cork bricks
Courtesy Sustainable Materials Cork bricks

Given cork’s impressive environmental performance, its use in architecture will likely increase. Cork oak trees are not cut down to harvest the material; rather, their bark is stripped every nine years. Additionally, the trees that comprise more than 5 million acres of cork forest globally can live up to three centuries. Like other cellulosic materials, cork stores carbon. Conservative estimates by researchers at Netherlands-based environmental consultancy CE Delft suggest that between 0.95 and 1.25 metric tons of carbon are sequestered per metric ton of harvested raw cork, and, like timber, this carbon remains trapped within the material until it is destroyed. Considering that discarded cork is routinely recycled into new products, it makes for an ideal carbon bank.

Recent analysis by Financial, a Brooklyn, N.Y.–based consulting firm, reports that “demand for cork in the building and construction sector is also considered a significant driver of the cork material market,” along with continued use as bottle stoppers. This is great news for an industry that recently faced a crisis. But how long will supplies last?

The cork industry is unconcerned about resource limitations. Given the inherent renewability of cork, exporters oversee a steady, replenishing supply of the raw material, and local regulations typically prohibit stripping trees prematurely. According to J.L. Calheiros E Meneses, president of the National Cork Industry of Portugal, cork oak trees comprise nearly one-third of Portugal’s forests. Furthermore, cork oak forests continue to expand in Portugal as well as Spain, two of the leading cork producers. Thus, no concern exists related to the supply side of cork—although the industry is monitoring the potential effects of climate change, including possible abbreviated tree longevity and growth.

For U.S.–based architects, a more common limitation concerns the need to import cork from overseas. Although Quercus suber treesfrom which cork is deriveddo grow in the U.S., the material they produce is not considered commercially viable. The requirement for import is one reason that cork remains a more expensive alternative to many surfacing products. Nevertheless, the cork industry is celebrating the rediscovery of its material’s many advantages. According to João Rui Ferreira, head of the Portuguese cork association APCOR, “We are living in a historic moment for cork. We have a new confidence, and we see a changing perception of the cork industry.”