But the firm was most impressed with its sustainability, as were the clients, the musician Tom Hardy and his partner, the textile artist Jo Gaskell.

“Cork as a building material has much to recommend it,” Mr. Hardy said via email. “It is itself a sustainable material, as trees are not destroyed in its harvesting. It has great insulating properties, both for heat retention — we rarely have to turn on the under-floor heating — and for sound — I use it as a recording studio. It is also aesthetically very pleasing. It has practically a zero carbon footprint.”

Mr. Hardy pointed out that its use in architecture also offers cork manufacturers an alternative market at a time when winemakers are using more twist caps. A natural material that is moisture- and mold-resistant, fire retardant, biodegradable and recyclable, cork is the bark of the cork oak tree. Its first harvest occurs when a tree is 25 years old, and the bark, which is able to regenerate, is then extracted every nine years in a process called stripping.

All cork roads lead to Portugal, which is home to the world’s largest area of cork oak forests, covering around 730,000 hectares, or 1.8 million acres. “Portugal can be proud of being a pioneer in environmental legislation, since the first agrarian laws that protect the cork oak forests appear in the early 13th century,” said Joel Esperança, a co-founder of Contaminar Arquitectos in Leira, Portugal. Not surprisingly, the country also produces half the world’s cork.

To the east of Lisbon, the insulation division of Amorim, a cork production company with a 150-year heritage, supplies most of the world with cork for insulation and facades. Ground into granules, cork is formed into expanded insulation corkboard through heat and pressure that releases the cork’s natural resin — forming the glue that holds the cork together, without additives, in rectangular panels.