The battle's on for vintage architecture

You could not pick two more violently opposed subjects than, on the one hand, yin and yang, and, on the other, Modernist architecture. The former implies a dynamic fusion of opposites, the latter an unequivocal clarity marked with sharp divisions of purpose. But rules demand exceptions, and 120 kilometres due north of Madrid, just outside the town of Gumiel de Izan – bingo! Here, the trefoil form of Norman Foster's Portia winery, which will be opened by the king of Spain in September, hunkers into the dry earth like a fallen chunk of the Skybase from an episode of Captain Scarlet and the Mysterons.

By instructive coincidence, 20 miles west at Peñafiel is the Protos winery by Lord Richard Rogers, described in these pages two years ago. This is a building in which structure and the wine-making process are unashamedly dramatised. And, if weighed against each other, these two arch-Modernist wineries suddenly suggest a trace of oriental mystique: the yin of Rogers's Protos building, in its architecturally yielding and lavishly tailored femininity; and now, by utterly stark contrast, we have Foster's tough and tightly focused architecture at Gumiel de Izan – unquestionably a man-winery.

There are those who might think satirically of Lord Foster as architecture's Captain Scarlet, a supermarionated figure, self-created by his own astonishing drive and imagination. The image is not trivial: his self-confessed boyhood addiction to Dan Dare comics put him on the road to his clinically achieved Damascus. And there's no doubt, either, that Foster's obsession with functional and formal precision lies at the heart of his architectural soul.

The legendary graphic designer Otl Aicher, profoundly admired by Foster, said of his buildings: "There is no zeitgeist experienced here, no world feeling. One sees one of the best possible solutions to a set of questions." And that is exactly what you get at the Portia winery – an absolute concentration, in concrete, glass and steel, of viniferous causes and effects that will ultimately generate a million litres of wine annually. If you want an architecture of controlled conditions, Foster is in a class of one. In terms of grapes in and wine out, and of form in relation to landscape, there surely cannot be a more logically efficient winery in the world.

Yet this is not so obviously a Foster building. It isn't smooth and seamless; nor shiny; nor does it strike one as obviously hi-tech. There are only two possible Fosterian clues: the first is the practice's tendency to shy away from creating a thoroughly convivial entrance; and the second is the winery's one blatant missed design opportunity. More on that later.

The fact that the Portia winery is not an instantly recognisable, die-stamped artefact from the Foster production line makes it notable. There is only one other recent Foster building that also defies the norm, or Norm: the Elephant House at Copenhagen Zoo, and, like it, the winery has a form and materiality that is unexpected. Why? Because in both cases, the practice was dealing with unfamiliar functional needs.

And so, by Foster's world-domination standards, the winery is almost a back-to-basics student design project. The only difference being that the "student" here is a thousand-member organisation with unmatched research abilities. If any practice was going to find out the shortest functional and formal distances between A and B in wine-making, it was going to be Foster + Partners.

The language used by Foster's project director, Pedro Haberbosch, gives a flavour of the intense determinism and control at the heart of the design. Standing on a gantry above the gleaming rows of vast fermentation tanks, he said: "Winemaking seems a linear, temporal process. But when you start analysing it, you realise that there's a tremendous amount of toing and froing involved." Only a Modernist would leap to that tidy "linear, temporal" assumption.

And order has, indeed, been imposed. The progress of tempranillo grapes, from delivery, through fermentation, holding tanks, and bottle filling has been absolutely rationalised in terms of space use and the way the whole system has been programmed. If added together, the entire physical length and volume of the process adds up to 200 metres. By using a trefoil form, with the holding tanks at the subterranean crux of the form, the wine never has to move more than 50 metres. The critical fermentation process is controlled by just three people.

The winery is set into a slope with a 12m drop from its highest point. This means that the star-point containing the fermentation hall is above ground, allowing carbon dioxide build-ups to be easily vented; it also lets daylight into what is a very strikingly tanked space. The wings containing the barrels and the bottle cellar are partly sunken below ground to provide the best conditions for ageing the wine.

This design strategy has also reduced the building's visual impact on the landscape, and improves its passive environmental performance, which is founded on the thermal mass effects of the densely ribbed internal concrete structure. The roof will eventually be fitted with a 6,000 sq m array of photovoltaic cells, and also be used to harvest rainwater to irrigate local vineyards.

These design elements, claims Pedro Haberbosch, accentuate the character of the wine-growing terroir, and wine-making skill. The decision to envelop the structure in hundreds of fast-rusting Corten steel scales – they weigh 90 kilograms each – is part of that. Less meaningful are the panels of oak bin-ends fixed to the walls of the reception space: they seem horribly appliquéd and clichéd.

There's no doubt that the Portia winery's industrial performance will meet the demands of its owners, Grupo Faustino. But what of the winery's non-industrial performance? Its planned Michelin-targeted restaurant is likely to draw hordes of middle-class gourmets from Madrid and Valladolid every weekend. Many will surely find the architecture sombre, above ground. And, crucially, the reception area does not relieve this impression in the slightest.

A great chance has been missed to create a really thrilling moment of entry. Instead of giving visitors an immediate downwards view on to those gigantically gleaming tanks in the fermentation hall, the sight has been blurred to near-opacity by a barrier of green glass behind the reception counter. And this is surely a doubly unfortunate visual mistake: in such a strongly geometric building, which is otherwise interesting to tour, this glazing kills any immediate understanding of the building's trefoil structure.

Haberbosch admitted that this design detail had provoked considerable discussion. From the outside, you can't tell the building's a winery. And, despite those box-ticking bin-end features, there's still no immediate and compelling winery vibe when you enter.

Yet Lord Foster says that visitors "can follow the process of the grape as if they were visiting the gallery of a cathedral". But they cannot. In a cathedral, you see and feel almost everything important the moment you enter. Therefore, kindly remove the glazing in reception entirely, or replace it with ultra-clear glass.

A TOAST: FINE WINE CENTRES

Protos winery, Spain, by Richard Rogers

This building doesn't want to hide; it wants to flaunt its presence in the spaghetti Western landscape. Beneath a dramatically formed roof lies the lavish drama of its subterranean, but clearly visible, fermentation tanks, and a typically generous covered plaza – a Richard Rogers trademark.

Dominus winery, California, by Herzog and De Meuron

The Swiss duo's design mixed a rectilinear Modernist outline with a visually subtle approach to materials and landscape. The winery has gabion walls made of big metal baskets filled with local basalt rubble. The result: thick, but air-porous architecture that blends into its setting.

Loisium winery, Austria, by Stephen Holl

The wine centre's design concept is based on the geometry of nearby wine vaults. Some of the angled "cuts" in the structure are glazed in recycled bottle glass, which casts green light in the interior. It's partially buried, which sets up an interesting journey to the vaults.

Lopez de Heredia, Spain, by Zaha Hadid

This small pavilion and tasting room created for the Tondonia winery is a vividly sculpted shell that contains a historic wine store. Perhaps unexpectedly, old craft and radical parametric design agree to differ, without spite.

For further reading: 'Wineries with Style' by Peter Richards (Mitchell Beazley, £30). Order for £27 with free postage from the Independent Bookshop: 08430 600 030