 He may be one of the original hippies - imprisoned 40 years ago for conspiracy to pervert the course of public morals as one of the "Oz Three" - but today, Felix Dennis, the maverick publisher, is breaking ground again. Together with cutting-edge architects Glenn Howells he has planned what could possibly be described as the most extraordinary new home in the country.  With a steeply pitched thatched roof and lime wash-rendered wattle and daub walls, at first sight the house, which will be set in 26 acres of woodland in Warwickshire, looks as though it could be the nostalgic reproduction of an ancient British chieftain's hut.  It will even use prehistoric insulation techniques such as a turf roof and wood-burning heating. Yet 21st-century materials and technologies, such as rainwater harvesting, a combined heat and power scheme and renewable energy systems, combine to make the building both carbon neutral and architecturally outstanding.  approval for the plans was given under the "PPS 7" rules for a landmark design and provides a rare exception to the rule banning development in rural areas.  James Way of agent Knight Frank (01789 297735), who is selling the site, called Blenheim Hall, with planning approval in place, says he has never seen anything like it. "It's a very large house, yet will tread lightly on the planet and virtually all the materials for building it will be sourced from the Dennis estate."  Dennis worked closely with the architects over a long time, testing and rejecting various models. He says everyone was determined "from the outset to create a spectacular house that would be as close to carbon neutral as was conceivable.  "Because Blenheim Hall is on a spectacular site on the brow of a hill we knew we would have to strive for a design that incorporates as many natural and local materials as possible, and that if we did so we would have a better chance of such a huge building sitting comfortably in its own skin. Not being an architect it's a miracle that this has been achieved," he says. The property will have a master suite, guest suite, staff quarters and luxurious leisure wing.  another futuristic "eco" house on an ancient British theme, this time designed around the earth-sheltered long-barrow idea, is also seeking planning permission under PPS 7. Wickfield House, designed by DSH architects for a plot near Cheltenham in Gloucestershire, is designed to generate its own electricity, collect its own water and treat its own sewage. The home will feature a domed, turf-covered limecrete roof built from excavated stone from the site.  The design, which has not yet received permission, has attracted mixed comments, including the expected "Teletubby" criticism. architect Dan Stainer-Hutchins says the earth-sheltering is both paying homage to the Neolithic sites in the area and also, with the use of on-site natural materials, is an obvious choice for a low-carbon building. Plot and build costs start from ?600,000.  Large country houses are usually notoriously profligate in their energy use, which is why Blenheim Hall and the earth-sheltered dwelling, both designed on country house scale, are so unusual. Indeed, whatever the size, until very recently, good design and low carbon have not sat together well with architects, says John Christophers of associated architects, himself the proud architectural awards.  "You either get beautiful, profligate architecture or rather uninspiring 'eco' homes. I hope my house shows you can combine the two, " he says.  Very different to Blenheim Hall is John Christophers's modest four-bedroom end-of-terrace in Balsall Heath, Birmingham - but with some rather exciting extensions.  While the front of the 1840s red-brick semi has been largely unaltered, the side is extended with timber and render cubist boxes and the rear is modernist, its simple white render and deeply recessed windows reminiscent of Le Corbusier. The house is dizzying in aspect, but despite its avant-garde appearance, inside it is a lovely family home. With no bills.  "Even on a cold winter's day the hot water from the solar panels is a delightful 63 degrees," says John, who lives in the house with his wife Joe and five-year-old son Theo. "Despite all the technologies, you don't need a physics degree to run it - it flies by itself."  another futuristic eco house, this tim 