On a site outside Manchester, Barratt Developments is building what its chief executive, David Pretty, calls an "eco-village".
Well, there will be seven houses incorporating every planet-friendly device on the menu, starting with a hole in the ground 16 metres deep to suck carbon-free geo-thermal heat which apparently can be found oozing up from the earth's core at that depth.
The idea is to produce homes that will qualify for the top score on the eco-measure the Government has decreed must feature in the home-buyers' report which must accompany every property that goes on the market from next year.
This kind of thing doesn't come cheap.
It may add £20,000 or more to the cost of a home that would sell for, say, £200,00 without the green trimmings.
Affordable housing this is not, in John Prescott's sense. But it should be cheaper to live in.
To establish how much cheaper, Barratt has commissioned a cost-benefit analysis from Manchester University, no doubt with a sliding scale to show how the benefits rise - or fall - with future ups and downs in gas and electricity prices.
The fixed element is the up-front price of the place.
At this stage there is no telling the extent to which banks and building societies will be prepared to lend against it.
There is a non-financial cost, too. The kit that makes a house ecological is bulky, much of it designed in America or Australia where there is more room. In a British-sized home it takes up a lot of what would otherwise be valuable cupboard space.
It also requires a garden shed to keep it out of the rain and apparently modern home-buyers don't like sheds. Half-joking, Mr Pretty is tempted to call them "outdoor maintenance facilities".
The whole thing seems far-fetched in a world where first-time buyers over much of Britain need something like double an average salary and a £20,000 deposit to get going. Existing home-owners seeking to trade up mostly do so to get more space, not a house cluttered with state-of-the-art eco-gizmos.
Yet Barratt is a hard-headed outfit, claiming to be Britain's biggest house-builder with a taste for 'brownfield' sites where it can put up a least 100 homes - witness Centenary Plaza in Birmingham.
It doesn't spend money on touchy-feely experiments just to establish vague green credentials.
This a serious project to get to know the economics and practicalities of building - and then finding buyers for - the most ecologically sensitive homes that can be designed a round present-day technology.
It needs to know because some planning committees are setting ever more demanding eco-standards - and the biggest constraint on any British house-builder is the time spent obtaining planning permission. Those that don't get planning don't build and don't make money.
Some councils, says Mr Pretty, already expect a builder to provide not just a bicycle shed but a bike to go in it, in the hope that the proud new homeowner won't drive around so much.
And that really wasn't a joke.