There's good news and bad news for modernists commissioned to bring exciting new houses to leafy Hampstead. One built his house and won a prize. The other, reports Nonie Niesewand, was cut off at the computer.

The London architect Rick Mather won an award of excellence from the American Institute of Architecture on Tuesday night for an angular, modern glass house in Hampstead.

Built on a steep slope, the house is actually on three levels - four counting the roof garden - with gardens on the lower two levels and the upper master bedroom suite opening on to a roof terrace. A roof light beams natural light down through the core of the house, and rather than letting it stop dead at the living-room level, he inset into the floor a toughened glass slab 3m x 4m - "Sure you can walk on it, my client Hoovers it" - through which the light floods the swimming pool below. Sometimes the owners float in the pool looking up at the clouds.

"This is a house that can be enjoyed from a lot of different positions, without feeling like you're going into a barn," says Mather.

It is a very calculated building in its orientation which makes the most of the site, not just for the views and light but for ecological reasons. All Mather's buildings have an energy conscious programme built into them which he describes as "no big deal, not particularly technological but good common sense". The only architect to design student accommodation at the University of East Anglia which has no central heating yet stays warm through winter - and has a waiting list, it's so popular - Mather saves his scorn for a high-tech approach which uses energy-saving technology to make up for a loss elsewhere. "There's no point, for example, on a south-facing house putting photovoltaic solar cells on the roof to power the air conditioning." Instead, he super-insulates and ventilates houses. In this house, unwanted condensation from the pool heats the house via radiant panels underfloor. The pool is ozone treated, which means no chlorine smell. Rainwater is collected in a cistern in the garden for irrigation of the roof terraces, as London water limes up irrigation pipes. Atelier One helped with the structure and Atelier Ten with the services and Doug McIntosh was his project architect.

Mather's hawkeye for detail is very evident - there isn't even a glazing bar at the right angles of the windows. Etched glass slats angled like louvres on the terrace capture the garden view and the light, while screening out the less appealing bits of neighbouring houses. A low glass wall doubles as a wind shield on the roof terrace.

But clients, as Frank Lloyd Wright once memorably informed us, have to have somewhere "to eat, seat and sleep, confound them". So now the owners have called in an interior decorator, Chester Jones, ex Colefax & Fowler, to furnish the living space with his wife Sandy's rugs and a wooden bench and bookshelves. "There's lots of drama in this house," says the client. "And I was frozen, paralysed when I first moved in. My husband's a minimalist so he prefers not to hang anything on the wall but I wanted to warm it up a little. Just the open-plan living and dining area."

But at roughly the same time as Mather was receiving his prize, a brilliant, white shell house designed by Ron Arad to be built on a site also in Hampstead was vetoed by Haringey Council. Both sites are leafy streets full of period- piece houses within walking distance of Hampstead Heath. But the residents confronting Arad's showmanship in their back yard were all up in arms at the idea of the new kid on the block, while Mather's are a friendly lot who all pitched up at the housewarming last Sunday. Both plots of land already had existing houses which had to be demolished to make way for the newcomers. Arad had to take out an undistinguished vaguely Arts and Crafts house, Mather a Fifties garage with two flats for housekeeper and chauffeur who worked at an adjacent Georgian house with Luytens additions. Planning permission had previously been given to a property speculator for a pair of neo-Georgian semis. But there the comparison stops. Arad had to win over Haringey, Mather had Camden Council.

It's enough to make the would-be residents of Arad's shell house want to sell their plot of land. But they are appealing to Haringey Council. Having read the planning officers' reports, Arad says the documentation which they presented to the planning committee was riddled with factual inaccuracies and created "an extremely misleading view both of our proposed new house and of the worth of the existing building". He is angered by the events.

"Haringey Council sent a clear message. While it is content to see the character and appearance of its conservation area eroded by over development, crass architecture and insensitive renovation and extension, it's not prepared to support architects or property owners that seek to improve its heritage." So maybe that familiar image of the shell house, first seen in August in The Independent, will make it off the computer screen and on to site one day. Let us hope so. Haringey Council hide their prejudices towards modern architecture behind their protection of a 1920s speculative building that even English Heritage could see no point in saving - and that they, at best, can describe only as "good enough". This isn't good enough. A review of planning committees is long over-due.