19th-century Guardia Civil post becomes bioclimatic home in Sanlúcar de Guadiana

In Sanlúcar de Guadiana, Andalusia, a 19th-century Guardia Civil border post has been transformed into a 76-square-meter bioclimatic house named Piedra y Agua. Designed by Estudio Zurita and Kalibra Arquitectura, the home preserves the original stone walls and uses passive strategies like thermal inertia, cross ventilation, and a photovoltaic system to eliminate the need for air conditioning. The project reuses existing materials: roof beams became stairs and kitchen elements, and the same cement used for floors was applied to countertops, showers, and sinks. The house has no interior doors, relying on wall thickness and orientation for privacy. A laminated wood loft adds a main bedroom and library, accessed by a staircase made from leftover roof beams. The single window opening frames the Guadiana River view. The design respects the site's history, with original loopholes now serving as light inlets.