Welcome to the Future of Air Conditioning, says a poster at Venice airport, straight after passport control. Next to the words is an image of a composite Shanghai/Dubai-like city, made of sealed towers of the kind that would be impossible without artificial air. Any association with this year's Rolex-sponsored Venice Biennale of Architecture is coincidental, but the poster is an eloquent exhibit of the event's main theme. This is: thousands of years of architectural history are being changed utterly by modern techniques of constructing and servicing buildings which, predetermined by technical considerations, make architects marginal to their making. If, for example, a fireplace was once an occasion for social gathering and ornamental embellishment, there are now sensors that can track an individual and provide heating specific to that one person. The provision of heat becomes a solitary, dematerialised and invisible affair.

The point is made in the large central pavilion at the heart of the Biennale's gardens. Here, this year's director, Rem Koolhaas, together with students from Harvard and a considerable team of collaborators, has installed a series of rooms which represent the elements of architecture – doors, stairs, walls, balconies and so on – and their contemporary versions. It is a 3D Google of what buildings have been and are now.

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The message is delivered in a different way in another Biennale venue, the long and venerable rope-making works of the Arsenale, where Italy is surveyed in all its splendour and squalor. The country, says Koolhaas, "has amazing gifts, but has difficulty realising them". In this, it might stand for all developed societies.

At other biennales, Italy is the uninvited host, on account of the fact that it ceded its supremacy in new architecture some time ago. Here it is laid out for inspection, like a body on a slab, in a series of exhibits arranged according to geography from south to north, starting with the modernist buildings Mussolini built in the colony of Libya. It proceeds via the contemporary arrangements for dealing with illegal immigrants on the island of Lampedusa, halfway between Sicily and Tunisia, all the way to the Sikh festivals that now take place in the Po valley, and ultimately to the Alps.

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The Biennale is greatly enhanced by the fact that, unlike its predecessors, it does not pay tribute to the big beasts of contemporary architecture (Koolhaas excepted) and the absence of their honking and rutting adds greatly to its enjoyment. They are represented mostly by a panel of door handles, each designed by a famous name and each only slightly different from the others, a microcosm of previous biennales that is eloquent in its pointlessness.

At times, this year's biennale is only obliquely about architecture (it includes, for example, dance performance), but as architecture is usually best experienced obliquely, this is a strength. Shows like this can be a wearisome tramp through information, but this one is stimulating. It doesn't offer answers, but the questions it raises are pertinent. You couldn't ask for more than this.