Low carbon homes are more airtight than their conventional counterparts, with better insulation, and rely on renewable sources of power generation such as roof-top solar panels or community-scale plants converting food and other waste into energy.
In more extreme examples of green homes, door-mounted letter boxes and fireplaces aren't allowed because of the draughts these allow in, said John Craggs, deputy chief executive at Gentoo, property leasers and developers, at the conference which drew 57,000 registrations, up from 40,000 last year.
"It's not that high tech, it's the precise detail. You don't just allow a guy to drill a hole (for cable television)," Craggs said of his company's planned, 28 so-called passive houses which are super-airtight.
"We're producing a guide for people on how to live in them."
The annual British, new-build green home market has reared from almost nothing to a 4.8 billion pound ($7.22 billion) industry in Britain in just five years, as the government ratchets up green construction standards to tackle climate change and fuel poverty.
That adds to a potential 390 billion pound market to upgrade existing homes, property developers estimated.
"What you see here is people planning for the future," said Neil Jefferson, chief executive of the Zero Carbon Hub, a government and private sector-funded agency meant to coordinate efforts to cut carbon emissions from housing, describing the annual "Eco-build" exhibition in London.
"There's a tremendous buzz."
Nevertheless, it would be "hugely difficult" to change architects' mindsets, said Quinlan Terry, a partner at architects Quinlan & Francis Terry which specializes in traditional building. Terry was referring to a design approach in the last century which had assumed permanent, cheap fossil fuel energy.
CODES
Britain introduced in 2007 new codes for house builders, on a 1-6 ranking where code 6 is zero carbon, based on waste, efficiency and renewable energy standards.
From 2016 all homes will have to be zero carbon, a standard which only a handful meet now.
Many property developers want the definition of "zero carbon" eased, so that instead of building a new home which exclusively uses energy from solar and other renewable sources, they can pay into a fund which cuts the equivalent carbon emissions elsewhere -- for example from existing homes nearby.
"There may be a cost per tonne to buy that off," said Stephen Stone, chief executive of property developers Crest Nicholson, adding that small developers would especially struggle whereas his company could invest in low-carbon heating and power for larger developments.
"What the industry wants is a fund-based scheme, especially for smaller developers," said Jefferson.
Already a quarter of the 125,000 new homes built annually in Britain are code 3, which may for example have water-saving toilets and washing machines and thicker, more insulated walls.
The trouble is that building an even higher standard, zero carbon home adds more than 20,000 pounds to the 100,000 build cost of a typical conventional alternative -- a premium people were reluctant to pay, said Jefferson.
"The British buying public is not as informed as they should be on the benefits of zero carbon homes. They're warm, they're comfortable, cheaper to run," he said Jefferson. "We need a marketing campaign to prime the market."
One problem was the pitch -- many people didn't care whether or not a house emitted less carbon dioxide (CO2), but were interested if it saved them money, said Stone.
"CO2 is a turn-off, it needs to be linked to running costs, something tangible in people's pockets." The British government has introduced this year new incentives for home "eco-upgrades."
