Cork House: the eco-friendly dwelling shortlisted for the Stirling Prize

Think of a material that can be used in a spacecraft’s heat-shielding and in top-class competitive sport, that is essential to high-end viticulture and that is being used in cutting-edge architecture, and you might come up with any number of advanced plastic polymers or metal alloys recently dreamt up in a secure laboratory. But the revolutionary material in question is nothing other than cork: essential to champagne since 1688 and Pierre Pérignon, perhaps, but generally overlooked.

Yet while cork — the bark stripped from a type of oak primarily found in the Iberian peninsula — has been used since ancient times for bottle stoppers and fishermen’s floats, being light and waterproof, its many other qualities are increasingly valuable in the modern world, and new uses for it are being discovered all the time. Perhaps the strangest of those uses can be found in a 44 sq m small house on an island in the Thames at Eton: Cork House, as the name implies, is a tiny dwelling built almost entirely from the stuff. It has been unexpectedly shortlisted for the Stirling prize, awarded annually to the country’s best new building.

Constructed by the architect Matthew Barnett Howland, with his partner Dido Milne and the help of Oliver Wilton, an old friend and colleague from University College London, it started out as an attempt at “rethinking the wall”. As Howland points out, in modern homes the simple wall has become, well, ever more complex. Nowadays it is made up of a weatherproof exterior, often of brick and mortar; a damp-proof course; a cavity filled with insulating material; an inner wall, usually of breezeblocks; plus wall-ties and ventilation of some sort; then plaster and paint.

Yet cork — which is breathable but impervious, provides insulation and is insect-proof and strong under compression, scrubs up into a rich internal finish and provides soundproofing — could do all of that and more in one layer. And it even smells nice. In fact, being so lightweight, it could be used for the roof, if stacked up as in the prehistoric Celtic beehive houses found in parts of Scotland and Ireland (and held down by five large glass skylights, without which it might blow away). So there’s even an element of archaeology. “The form largely chose itself,” Howland says.

Perhaps the cleverest part of the project was spotting the environmental benefits of using the waste wood left over from traditional Mediterranean cork forestry (which is sustainable and contributes to biodiversity) as a building material. Cork cultivation may be a multibillion-pound industry, but no trees are harmed in the process, which involves cutting off a sheet of bark every nine years by hand, and nothing is wasted. Since the offcuts that Howland used were placed in pressure cookers and bonded together in their own resin, called suberin, no chemicals or glues were required. The result was a series of impeccably eco-friendly blocks, 3D-milled by a robot, that could be slotted together without mortar, like a giant Lego set.

As a result, the house was carbon negative at completion and has been assessed to have the lowest amount of carbon emitted over its 60-year life span for any building that the carbon assessor had appraised. That sum is less than 15 per cent of a new-build house, and the cork can be recycled once more at the end.

The house uses waste wood from Mediterranean cork forestry

“I wanted to see how simple I could make the wall,” Howland, 50, says. “Which is not only super-complex across the life span of a building, but a bloody mess when it comes down. The overarching idea was to take a whole-life approach to carbon and think about what happens when a building reaches the end of its life. And since buildings often survive us, we should be thinking about what we leave behind.”

If that’s a slightly morbid note, it should perhaps come as no surprise: Cork House started off as a collaboration with Howland’s father, who died in 2013 and left money for its completion (Howland won’t give the exact cost, but it did not come cheap). “It seemed like a nice thing to do to see it through,” he says. And there were other dark days, not least because of “the time it took. It feels like I’ve done nothing but drive the project to completion for five years now.”

Its eco-friendly credentials include being carbon negative at completion

Yet it might soon prove to be all worthwhile. It could pave the way for future developments — cork and timber hybrids of two or three storeys could be next, as could homes of pure stone, a material that shares some of the necessary characteristics.

Cork House is up against some strong competition for the Stirling, not least the £1 billion redevelopment of London Bridge station — “which shows what civilisations can do when they get their act together”, Howland says magnanimously — but you wouldn’t bet against discerning judges choosing something that redefines what the simplest architectural typology of all, the house, can be.

Cork House has only an outside chance for the Stirling at odds of 5-1 (London Bridge Station and Nevill Holt Opera in Leicestershire are the present favourites). Yet whether or not it wins, being clever yet modest, and beautiful but earthy, there’s no doubt that it really is a bit of a corker.