The walls are clay blocks glued together and the insulation is sheep’s wool. Welcome to Prince Charles’s vision of the future of the British house - made from natural materials, grown or taken from the ground.

The project, known as the Natural House, has been drawn up by the Prince’s Foundation for the Built Environment. A trial version will be erected on a site near Watford, Hertfordshire, on January 5, with the know-how likely to be used for new homes at Poundbury, the prince’s model development in Dorset, or at one of its other two dozen sites across the country.

The foundation, an educational charity that studies building design, set out to create a house that would save energy, be easy to build and appeal to the “increasingly eco-aware builder”. (The government has said that all new homes built from 2016 must be carbon-neutral.) Unlike most green houses, however, it is not ultra-modern in design, but traditional - reflecting the prince’s conservative taste in architecture. Its features, more 18th- than 21st-century, include a hipped roof, casement windows, columns, chimneys and railings.

“We assume that low-carbon must mean high-tech, but that’s not the only option,” says Hank Dittmar, chief executive of the foundation. “We begin with looking at what’s worked in the past, then we apply technology, while a lot of the green houses start with technology, then apply a design creativity.” The prince was shown a sketch several weeks ago. “He’s looking forward to seeing it built,” Dittmar says.

Surprisingly, perhaps, the house does not have solar panels or wind turbines, although these could be added. “We try to solve renewable energy problems at the neighbourhood scale, rather than at the scale of the individual house,” Dittmar explains.

The test building, expected to be completed by May, will be a pair of semidetached homes, one a conventional three-bedroom house, the other combining workspace downstairs with a flat upstairs. It is expected to remain at the site for two years. Peter Bonfield, chief executive of the Building Research Establishment, which is working with the foundation, says such houses could eventually be cheaper to build than conventional ones.

The plans attracted mixed reviews from architects after details were published in Building Design, an architectural magazine. “All the materials are great, but why they have fixed themselves to retro-Victoriana is beyond me,” said Bill Dunster, an architect behind a number of green projects. “It doesn’t seem to have progressed much beyond the 1850s, although it may have a bit more insulation.”

Dittmar rejects this criticism: “The British home-buying public generally prefers the traditional home, so we think making this kind of design will increase the uptake of green housing. It’s not ideological, it’s practical.”

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