Comparing Passivhaus and Spanish Ventilation Models: A Study with Three Apartments in Northern Spain

Over recent years, energy efficiency regulations in European construction have aimed at maximising the reduction of operational energy consumption in buildings. In the case of Spain, regulations have progressively implemented energy reduction measures based on improving the insulation capacity of the building envelope, coupled with the integration of mechanical ventilation systems for improved ventilation. This transition, initiated in 2006 with the first regulatory document aligning with European directives for building energy efficiency, has seen successive regulatory updates limiting primary energy demand. The inclusion of indoor air quality control measures, alongside the need to minimise heat loss via ventilation, has strongly favoured the implementation of heat recovery ventilation (MVHR) in the coldest climatic zones for compliance with the new regulations. Anticipating this process, some administrations, such as that of the Basque Country, had built some unique housing developments using energy certification systems originated in central Europe as a model, characterised by significant insulation and envelope airtightness, along with double-flux ventilation equipment with heat recovery. One of the cases under study was constructed to the Passivhaus standard, which conceives the ventilation strategy as the cornerstone of the residential environmental conditioning system. This work presents an analysis of the operation of a high-efficiency double-flux ventilation unit in one of the 171 apartments located in a collective housing building certified Passive House in Bilbao, Spain. It examines Indoor Air Quality and compares it with another dwelling in a similar development, and another in the same climatic zone designed with the typical ventilation scheme prior to the Spanish CTE building code. It was found that the ventilation equipment installed had enough theoretical capacity to fulfil Passivhaus requirements, but not the original or updated Spanish codes. Flow measurement of the real-life operation of the unit, however, showed the actual ventilation flux was not enough to comply with neither. In spite of that, CO
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concentrations in the Passivhaus apartment and in the two comparison dwellings were verified to be acceptable and significantly better than typical in the existing literature. Results highlight the potential for discrepancies between theoretical and real-life performance of ventilation and underscore the need of research into energy aspects of ventilation.