Family's gamble pays off: self-built house voted greenest in Britain is sold for profit of £625,000

When Aaron and Raphaella Curtis decided to build their own eco-home next to an unseemly half-demolished viaduct, their friends thought they were verging on insane. But now, just three years later, the couple are selling the country's greenest self-built home for a profit of £625,000. The house, which won an award last year for being the most environmentally friendly self-built home in the UK, has just sold for £865,000.

Built on a small piece of scrubland worth just £60,000, others had failed to see any potential in the site. The conversion of the brownfield site was one of the key reasons that the Curtis's eco-home stood out from the other green contenders in last year's sustainability award by the Royal Institute of British Architects.

They incorporated the original Victorian foundations of the crumbled viaduct into the design, as well as installing solar panels, state-of-the-art insulation and underfloor heating.

The family of 10 built the five-bedroom house in Lewes, East Sussex, specifically so it would have a minimal impact on the environment. But with eight children, the motivation for being environmentally friendly was also financial. "We've been running normal-sized bills on an abnormal-sized family," said Mr Curtis.

Self-building also had a financial benefit. They had been looking at properties to house their larger than average family and realised they were unable to afford anything big enough. Their choice of a small plot allowed them to build upwards and outwards without too much initial outlay.

It's like a Tardis inside", said Mr Curtis, 44. "It's built on a small patch of ground, but it cantilevers out so that there's plenty of space in the rooms above. We couldn't have afforded to buy a house like that".

Their building costs were just £240,000, as Mr Curtis managed the project himself using local craftsmen and materials. The carbon footprint of the building process itself was cut down by using locally-sourced materials wherever possible. The home, which also won the Norwich and Peterborough Building Society eco-house of the year award, used sweet chestnut wood from five miles away to clad the exterior. "It only cost a little bit more than Canadian Cedarwood", said Mr Curtis, "and we hardly had to move it any distance".

"We had all the common features to make the house so-called green, with solar panels and a condensing gas boiler, but we also kept down the miles we moved all the materials."

Duncan Baker-Brown, the architect who designed the building, was excited by the sale. "It's amazing they got that much", he said. "The site looked like a postage stamp; it's a real lesson in how profitable self-building can be. He hadn't built anything more than an extension before, so he gambled and it paid off."

Mr Baker-Brown, who works for BBM sustainable design, said that in recent years the eco-friendliness of a property was having a bearing on its value. "In the past three years, people have begun to specifically request green houses because they know it adds to the value and quality of a property".

The family are moving to a Georgian terrace in Lewes town centre. Mr Curtis admits "the Georgians weren't renowned for their eco-friendliness" but he says he has plans for another eco-build. "Two of the teenagers are leaving home, so we needed to down-size. But I'd still love to do it again in the future, and this time I'd make it zero carbon".