Take a decaying house of 1900, trapped in its city block, awfully oriented, and refurbish it while maintaining the original façade and volume: challenge accepted!
Low energy MZ House is the result of a neat and effective intervention by the architect/owner Marc Folch in the district of Sarrià, Barcelona. The architects' goal was to reach the Passivhaus standard with a quick and cheap work. The project consists in a wooden prefabricated dry construction chiseled with numerical control and assembled on site in only two days. The construction process was very accurate with a particular attention to ensure enough aritightness. The interior finishing is a well balanced mix of wood and plastering surfaces. Inside the walls run the pipes of the mechanical ventilation circuit that constantly refreshes the inside air with a heat recovery efficiency of 92%. The plan distribution is a total open space that enhance the perception of a large room besides the small plot area but, on the other hand, it doesn't always ensure enough privacy which could result essential in case of a family with children.
The project was mainly developed in section providing the continuity of the volume whith a full height space covered with a skylight. This design strategy was thought to get at once natural ventilation, daylight and passive solar heating, significantly reducing energy consumption and improving comfort.
The result is extraordinary even if the house didn't reach the passivhaus standard. The energy consumption for heating passed from 170 kwh/m2 to just 17 kwh/m2 a year. Nevertheless this strategy was probably not exploited at the maximum of its possibility due to a lack of accuracy in its study: The skylight could cause overheating in summer and may not be sufficient for passive heating in winter due to the obstruction that the same building casts to itself. The open space doesn't play in favor of the climate control: when the heating or cooling needs to be activate it will always heat the totality of the volume. The construction doesn't offer a good thermal inertia therefore the house is more vulnerable to the in/out difference of temperature both in summer and in winter. Probably the initial choice to aim at the passivhaus standard was not the correct one; the big effort of making the house as much airtight as possible was neiter successful nor 100% profitable.
However it is a good example of sustainable architecture which must be kept in mind whenever an architect approaches a refurbishment project.
