Historic agricultural buildings disappearing from British countryside Once an integral part of our rural landscape, historic barns and other agricultural buildings are disappearing from the countryside. Comparison of modern and old maps shows that over 70 per cent of English field barns have been lost since the mid-19th century, according to English Heritage. Fine barns, granaries and stables, already dilapidated when the listing process was introduced in 1947, were not listed and allowed to subside into the mud. Owners of Seventies and Eighties barn conversions know only too well the ruinous cost of heating them, often with oil or LPG, as they tend to be off mains gas, and these poorly converted barns are increasingly seen as white-elephant money pits. Yet new green technology is now playing a part in helping restore these "cathedrals of the countryside." Potter's Farm Barn, in Betchworth, in the Mole Valley, Surrey, had a rare four-bay pre-1750s timber-frame barn which was registered on a tithe map in 1634, yet its origins are probably pre-Shakespearean. Unlisted after the Second World War, it subsided until it was just an ivy-covered ruin. With one bay collapsed, it would have fallen down completely had it not been saved by James and Claire Benn. "We needed somewhere for Claire's textile teaching business," says James, a publisher. It was almost beyond saving but it is in a staggeringly beautiful location in the North Downs. An architect had a look and said 'I've seen worse' so that was that. "It would have been much cheaper to do basic insulation and shove in a boiler," says James. But we felt that this barn had been standing for 400 years, and, if it was worth rescuing then it should stand for another 400. The Benns have combined the ancient skills of a master oak carpenter with the latest insulation technology, including super-dense Steico wood-fibre panels and Boost'R 10 breathable membrane. The barn is heated from a ground-source heat pump and the main problem of converted barns (heat rises to the roof) has been solved with a mechanical ventilation heat-recovery system. It is now A-rated for energy performance, more efficient than most new homes. "The only way to save many of these new barns is to convert them to different uses," says Patrick Kennedy-Sanigar, the designer who oversaw the restoration. But no one wants to live or work in a draughty box costing thousands to heat. If you super-insulate them they are delightful to live in. Jon and Elizabeth Hutchings took on a 17th-century derelict barn in Stalisfield Green, high on the North Downs, Kent, and they hope to move in by July. "The barn was in danger of collapse," says Jon, a teacher. It was daunting but I was overwhelmed by the position and the wildlife. The children love coming here and planning their menagerie of animals. Like the Benns, the Hutchings are combining historic timber-preservation techniques with cutting-edge technology. The roof was originally thatched so we will bring that back. We are also going for ground-source heat pumps and new insulating materials. We will be able to retain as much of the glorious internal space as we want without worrying about heating bills.  Patrick Kennedy-Sanigar (spaceshuffle.com) will be exhibiting at The Listed Property Show, February 18-19: listedpropertyshow.co.uk