Claudio and Calvin

What do the latest wave of Calvin Klein shops and an idealistic cultural project in Germany have in common? The cool white minimalism of Claudio Silvestrin.

There is a Zen calm in Claudio Silvestrin's reflective, empty studio in Islington. Origami-like scale models of his buildings in New York, Germany, Provence, and Majorca run the length of a thick, low, whitewashed wall. Behind another screen wall, eight silent architects lined up at benches clear away all their papers every night to bare the refectory- style worktable.

This is Silvestrin minimalism, as exemplified in Jay Jopling's White Cube gallery in London and Calvin Klein's Paris store. Next year, it will be seen by many at Calvin Klein's big new London shop in Sloane Street and by the select few at his new New York apartment in Central Park East.

Calvin, newly divorced, has decided that the Silvestrin style reflects his life now. His married period in a shingle house in the Hamptons - deckchairs painted with Aubusson swags, white sunbeds and geometric rugs - has gone the way of his Escape perfume ads which used to show happy couples on boats and beaches. Now he's gone for monastic solitude, and in Claudio Silvestrin he has found the right architect.

There isn't a door inside the apartment Silvestrin has designed for Klein, except one for the john. Even the bathtub stands boldly alone in the middle of the apartment. Claudio is definitely anti-room. He talks zones and functions - sleeping, bathing, cooking, eating, dressing, never rooms. "Why should people buy a box and then box it in some more?" he asks.

The Calvin Klein store in Paris, which opened in May, signalled the end of Klein's commercial relationship with that other great maestro of minimalism, John Pawson, who designed the Klein flagship stores in Madison Avenue as well as in Tokyo and Seoul. Years ago, Silvestrin and Pawson were partners but broke up big-time. Claudio says the proportions of Pawson's Calvin Klein store in New York, with its lofty white space and sandstone floors, 20ft windows and monolithic stairs instead of escalators, are all wrong.

Klein's annual turnover is $3bn a year, what with his ready-to-wear and couture collections, his Y-fronts and his scents, so when he phoned Silvestrin and asked him to breakfast at Blakes Hotel in London, the architect knew it was the start of something big. Blakes is an unsettling place for a pair of minimalists, with its inky blackness pierced by beams of light, overstuffed banquettes and orchids. Klein and Silvestrin talked fashion and the importance of buttonholing.They discovered a shared enthusiasm for the artist Fontana, the canvas slasher whom Claudio first discovered as a 16-year-old in his home city of Milan. Claudio still slashes, or embosses, a wavy S-bend line into the baseboard of his scale models. And Calvin collects furniture by Fontana, who was Claudio's tutor in Milan and introduced him to the minimal aesthetic.

When his London store opens next year, Klein will launch for the first time in Britain his home-furnishing line of bed and bath accessories, and tableware inspired by his own possessions in, alas, the East Hampton marital home. Stoneware plates and bowls, and throws made from feel-good fabrics such as merino wool and cashmere are aimed at the hard-working professionals who wear Klein clothes. Everything is fashionably buff or white, and eco-chic too, with hemp-and-linen-blend duvet covers and unbleached linen bath towels as well as pineapple-fibre pillows. "Modern but cuddly," says Calvin. "Tailored but sensual."

So will Claudio, the least accessorised man outside a Calvin Klein ad, buy them for the Islington house he shares with Tessa and their two children? He thinks they won't be able to afford them. "And, you know, I'm not really interested in things, though the plates are nice."

Another Silvestrin client, not yet as famous as Calvin Klein but destined to become one of next century's most talked-about persons, is Karl Heinrich Muller. Muller has set up a foundation in Germany called Hombroich, which has just bought a former Nato rocket-missile launchpad to turn into a cultural centre. Here, international bio-scientists and sculptors, poets and philosophers, writers and painters will exchange ideas, hold seminars, and take a sabbatical in new buildings - commissioned from architects such as Silvestrin and Tadao Ando - that will stand among the old military ones. Silvestrin has planned a 30-bedroom cloistered hostel for visiting scientists and artists based on Cistercian architecture and a seminar building in the form of a double cube. (You can see the scale models for the Hombroich project at the RIBA Architecture Centre, 66 Portland Place, London W1 until 6 September.)

A secretive and low-key operator, Mr Muller, who made his fortune as a property developer, believes that art will age and die and so doesn't conserve his collection in hermetically sealed, light-controlled environments. Instead, he houses the works amongst the old army huts inside 11 walk- in sculptures, which function as pavilions where works from different cultures and epochs are shown, unlabelled, next to each other.

Forget conservation, experience is all. There is no lighting, but buildings are positioned to amplify the natural light. In one, two Yves Kleins are shown under a intense white light reflected from the polished white marble interior. Another pavilion facing west opens at both ends so that, at dusk, looking out from one end, the sky is still blue, while from the other, it appears red from the sunset.

Silvestrin calls Muller's Hombroich project the making of a miracle. "How can someone spend so much money and energy and time on a non-profit- making enterprise dedicated to the enhancement of the human spirit rather than material gain?" he wonders.

The architect sees no contradiction between Muller's miracle and Klein's materialism. One man is setting a pattern for the future in art and architecture, an individual exploration on which the visitor embarks, while the other is similarly driven towards making the world a better place through good design, fine tailoring and beautiful objects - at a price. Silvestrin is able to serve both.

When he spoke at the ICA about the spirit of Hombroich in a lecture called "Agri-architecture, Hombroich and the Hermetic", Silvestrin ended with a screening of a long prayer meeting in a Cistercian monastery in Provence - chanting, knee-creaking prayers, songs and psalms which cut 20 minutes from question time. The spirit of the project, he believes, is more important than the formn