Isolated at the fringe of a forest in the valley of Bagnes, Wallis in Switzerland, this barn was transformed and extended into a primary residence for a couple. Therefore, new volumes were implanted at the back of the barn, allowing a minimum impact on the main facades. On the ground floor, this new volume is set underground and hosts a garage, a bathroom, the entrance and the equipment room. The visible part of the extension on the first floor breaks away from the old barn with its contemporary cladding and roof overhang detail. The openings were sized accurately to frame particular views of the valley but also to respect the original building. The built-in furnishings were planned down to the finest detail in order to use every single space available. A very specific attention was given to the energetic consumption of the barn and to the quality of the construction materials, making it the first building of its type certified with the Minergie P label in Switzerland. In collaboration with the energy consultants at Acrowatt Sàrl, solar panels, photovoltaic panels and a double flow ventilation were integrated into the construction, which represented a real challenge given the nature of this building. During the construction, the barn was totally dismounted, when the pieces of the original planks were numbered, then straightened and remounted in a workshop. All the underground parts were built with traditional concrete masonry and the aboveground parts with new wooden frames. Finally, the old planks were laid down on the new construction in order to preserve its traditional aspect.