Analysis of the airtightness of the Basque Country social housing stock

Resumen

A detailed analysis of the airtightness was carried out in 35 social dwellings of the Basque Country in 2019. The aim of this study was to evaluate the significance of air leakages in social housing and its relationship with the energy performance of these buildings. This research allowed to assess the magnitude of the air leakages and to identify the main areas of infiltration. Besides, the results of the study were compared to national and European references in order to position the quality of construction of the social housing in the Basque Country. The tested 35 dwellings were selected among 11 buildings, as a representative sample of the social housing stock of the Basque Country in terms of the year of construction, HVAC system features and Energy Performance Certificate (EPC). The blower door tests were carried out following the UNE-EN 13829:2002 (updated recently by UNE-EN ISO 9972:2019). All the dwellings were tested under the method B of the standard to evaluate the envelope leaks. Additionally, 8 of them were also tested using the method A to measure the impact of ventilation and intended openings. For the analysis, several variables were taken into account, such as the typology of the dwelling, the number of bedrooms, the net floor area and the internal volume. In order to complete the study additional measurements were done, using an infrared camera to locate the main infiltration areas and a thermo-anemometer to assess the magnitude of the air infiltrations. The results revealed that there are no clear lineal relations between dwelling parameters as the internal volume and the airtightness of the dwellings. Neither the typology of the dwellings, nor the net floor area, the EPC or HVAC features seem to have a direct influence on the air leakages. On the other hand, a clear difference is observed when comparing the average airtightness of the 11 analyzed buildings, which suggests the mayor role of the quality of construction. The air exchange rate at 50 Pa (n50) ranges from a maximum of 7,0 h-1 to a minimum of 1,8 h-1 among the 35 tested dwellings. In the 8 housings tested in more detail, using methods A and B of the standard, the difference between both methodologies was significant and showed an average increase of a 31 % in the air changes per hour rate. The location of air leakage areas also showed a great variability among dwellings, although the main areas of air leakage were found around the windows and the boxes of roller shutters. Lastly, the comparison with up to date national studies showed that the airtightness of the Basque Country social housing stock is notably better, with average 4,0 h-1 against values that range from 7,7 h-1 in Spanish multifamily buildings to 7,0 h-1 in Spanish social housing.