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Air infiltration through the building envelope has already been proven to have a significant energy impact in dwellings. Different studies have been carried out in Europe, but there is still a lack of knowledge in this field regarding mild climates. An experimental field study has been carried out in the Mediterranean climate area of Spain and the Canary Islands in order to assess the air permeability of the building envelope and its energy impact. A wide characterization and Blower Door tests have been performed in 225 cases in Alicante, Barcelona, Málaga, Sevilla and Las Palmas de Gran Canaria for this purpose. The obtained mean air permeability rate for the 225 studied cases was 6.56 m3/(h•m2). The influence of several variables on airtightness was statistically analysed, although only location, climate zone and window material were found to be significant. Air infiltration has an energy impact between 2.43 and 16.44 kWh/m2•year on the heating demand and between 0.54 and 3.06 kWh/m2•year on the cooling demand.

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Air leakage and its impact on the energy performance of dwellings has been broadly studied in countries with cold climates in Europe, US, and Canada. However, there is a lack of knowledge in this field in Mediterranean countries. Current Spanish building regulations establish ventilation rates based on ideal airtight envelopes, causing problems of over-ventilation and substantial energy losses. The aim of this paper is to develop a methodology that allows the characterization of the envelope of the housing stock in Spain in order to adjust ventilation rates taking into consideration air leakage. A methodology that is easily applicable to other countries that consider studying the airtightness of the envelope and its energetic behaviour improvement is proposed. A statistical sampling method has been established to determine the dwellings to be tested, considering relevant variables concerning airtightness: climate zone, year of construction, and typology. The air leakage rate is determined using a standardized building pressurization technique according to European Standard EN 13829. A representative case study has been presented as an example of the implementation of the designed methodology and results are compared to preliminary values obtained from the database.

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