Science: How smart a house do you want?: Technology will soon be able to do everything in your house except pay the mortgage. Patrick Matthews wonders if we really need it

Is there such a thing as too much intelligence? Visitors to Japan have returned, appalled, with tales of hi-tech lavatories. The most common version has a habit of drenching inept Westerners; the most sophisticated offers an on-the-spot medical, sampling body wastes and providing an instant read-out on the user's state of health.

Microchips long ago began migrating from the home computer. They embedded themselves in the washing machine, the video camera and the home computer. Now, as the price of computing power falls, manufacturers need to keep demand humming. The next leap forward, they hope, will take artificial intelligence into such mundane crannies as light switches, power points and door locks. The idea is that houses will join in the revolution in automation which has brought about a behind-the-scenes transformation in office blocks and skyscrapers.

Until 10 July various 'intelligent homes' will be on view in Milton Keynes as part of the FutureWorld exhibition. Siemens in Germany, Merlin Gerin in France and Echelon, launched in the United States by one of Apple's founders, are among the hundreds of firms selling intelligent building technologies. John Porteous, chief executive of the British Automated Homes and Buildings Association declares: 'This is a market which is going to take off in the same way as video and satellite television. There will be a slow start, but after that it will happen relatively quickly.'

Dr Porteous warms to the prospect of life in a 'smart home'. 'If you're the last to leave in the morning, you press a single button that tells the system to go into work mode. And as you close the door, it sets the security, tells the heating to go back a few degrees and any lights go off. The same system anticipates your arrival back from work and turns up the heating and keeps the alarm set until you arrive, when it goes into evening mode. If it detects that it's dark outside it automatically scales the lights into a security pattern.'

Do we really need all this? The fact that a technology exists is not enough to create a demand for it. Without the big production runs created by real consumer enthusiasm, a new product may never become cheap enough to find a mass market. Do smart buildings possess the 'must have' quality that word-processing brought to home computers, or will they go the way of the pocket-sized television?

Architect Gabriele Bramante is designing the first building in Britain to incorporate the Siemens system: a Citizens' Advice Bureau in Chessington, south London.

'The thing that really appeals to me is to control a building down a phone line,' she says. 'I'd like to go in to work early, but the thing that puts me off is the fact that the office would be stone cold.'

She has designed the Chessington CAB with automation that specifically has disabled staff and clients in mind. Easy-to-operate controls and occupancy sensors link into the control circuit, or 'bus'. This in turn sets the lighting, heating and security systems.

Automating a building is not a new idea. In the Sixties, wealthy Californian hobbyists built special rooms to house the bulky computers required to run their homes. The bad guys in James Bond films or The Man From UNCLE are often to be found in palaces of automation, where a touch on a hidden button can seal off the hero's escape route.

Until recently a central computer was the focal point, with cabling that fed data on temperature and humidity back to it. This would trigger instructions to control pumps and switches.

At the Stock Exchange building in the City of London this central computer is housed in an impressive control room, built seven years ago, where the circuits are reproduced on giant 'mimic panels' studded with twinkling lights. Frank Hurley, the building services manager, who retains the beard he sported as chief of watch on a nuclear submarine, says: 'Somewhere like this is not at all unlike a ship - the systems are very close.' He likes the reliability of this 'hard wired' system.

But technological changes mean that a building can now have more automated systems than the Stock Exchange without needing a centre of operations. The trend is to have intelligence distributed around different areas.

A 'bus' system means that all sorts of intelligent devices can be linked on an inexpensive, single wiring circuit. Instructions and information are given an electronic address and are only acted on when they reach their specific destination. The heating and ventilation controls for the whole of London's Canary Wharf can be reached from a lap-top computer plugged in anywhere.

Honeywell, which made the heating and ventilation controls for Canary Wharf, now manufactures automated home technology for domestic users. Its 'Total Home' products are installed in one of the smart houses at Milton Keynes; these communicate with each other and the occupier via Honeywell's own purpose-designed bus.

But others in the industry see the holy grail as a common bus standard that can link devices made by a wide range of manufacturers. The idea behind much building automation is to get different systems - heating, lighting, security - to talk to each other. There are three 'open' buses in Europe, each designed for use by a club of manufacturers clustered around several protocols: that developed through the Esprit programme and adopted chiefly by Philips in Holland; 'Batibus', pioneered by Merlin Gerin in France; and the EI-bus from Siemens in Germany.

European standards authorities have been trying to narrow the range to a common standard appropriate for smaller buildings. Their labours have so far produced a common European standard which can specify any of three incompatible systems. 'A pointless fudge,' in the words of one expert.

'I think that people are looking for a solution which could be used world-wide,' says Barry Haaser, Echelon's European marketing manager. 'One of the strongest drawbacks of our competitors is that they're perceived as being a French or German solution.' Echelon's system, based around its 'Neuron' chips, has found takers not only in its home market, the US, but in France, Germany and Britain.

Competing bus systems are not the only problem. The bigger question is whether the technology will have a broad-based appeal. Disabled people are seen as a key target group. Gabriele Bramante points out that buildings which address the needs of the disabled should also be more comfortable and convenient for other users. The technology may also have a role in saving energy. Utility companies are looking at new and more varied tariffs; an intelligent washing machine which was able to read data sent by the electricity company, could be programmed only to wash a load at the cheapest rate.

Jeremy Bowman, marketing manager of Merlin-Gerin, has had to ask himself if systems such as his own Batibus will make the big breakthrough. His answer: 'Today it is impossible to sell a television without a remote control. But if you went back 15 years and said that people would insist on a device to change television channel from 6ft away, everyone would have laughed at you.'

(Photograph omitted)