Airtightness performance of the building envelope of dwellings in Spain. Characterisation and energy impact of air infiltration

Abstract

Only after the oil crisis in the 1970s has there been an undeniable growth in the level of interest in reducing the use of fossil fuels. In this regard, the countries of the European Union predict a sustainable, competitive and decarbonised energy system by 2050. For that purpose, it is crucial to address the energy efficiency of buildings, which are responsible for a significant percentage of energy consumption, and, therefore, greenhouse gas emissions. The potential seems obvious, considering that, according to the European Commission, 75% of the buildings in Europe are energy inefficient.In this context, uncontrolled airflow through the building envelope, or air infiltration, is a phenomenon that involves energy loss since it needs to be conditioned at the interior comfort conditions. Air infiltration is also related to the ventilation of buildings and, thus, has an impact on indoor air quality. In this sense, a relationship is established between air infiltration, energy impact and ventilation. Since airtightness is the main characteristic of the envelope that determines air infiltration, its study is essential to understand the performance of the building envelope.However, this issue has not been addressed in depth in most countries with temperate climates, and, specifically, in Spain, given the traditional dependence of air renewal on air infiltration. Currently, the implementation of controlled ventilation systems guarantees adequate indoor air quality in residential buildings. Therefore, air infiltration is no longer necessary as an air renewal source and, consequently, its reduction is a priority to achieve nearly zero-energy buildings (nZEB). In this sense, the airtightness characterisation of the envelope of existing buildings is essential to prioritise efforts and determine strategies for the renovation of the existing building stock according to the decarbonisation objectives which have been set at a national and international level.