Escuela de Politécnica Superior

In buildings, ventilation, or rather, a lack of airtightness facilitates air leaks, from the outside to the inside and vice versa, and is not controlled. Cold air enters through the enclosure, and warm air is lost to the outdoors, due to the poor hermeticity of the facades, roofs, carpentry, ducts, etc. In order to quantify the airtightness in multi-family dwellings in Madrid, 151 blower door tests have been carried out in multi-family dwellings built in different periods whose execution has been regulated by the UNE-EN 13829 standard. Through its quantification by an n50 value, the average values of 5.8 renovations per hour have been obtained in addition to detecting the main points where air infiltration occurs. The constant improvement in the transmittance of construction elements has indicated that the entry of outside air has a progressively greater relevance to the total energy consumed by the residential sector while facilitating the uncontrolled movement of air through the building envelope. This not only implies higher energy consumption but also generates a series of problems that affect the health of the occupants, such as a lack of thermal comfort, entry of pollutants and odours, noise, inadequate operation of ventilation systems, and less protection against fire.

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.

already established standards which aim to limit the energy waste through the envelope following the European Energy Performance of Buildings Directive guidelines. However, in Mediterranean countries there is still a lack of knowledge in this field. An extensive study has been carried out in order to characterize the air leakage through the envelope of the existing housing stock in the Continental climate area of Spain. Results of 129 dwellings tested, including different typologies and periods of construction, are shown. Blower door tests were performed, and thermal imaging was used to locate leakage paths. Single-family dwellings were found to be more airtight than apartments, given that the mean air permeability rate at 50 Pa (q50) was 5.4m3/h·m2 and 6.8m3/h·m2 respectively. The mean air change rate at 50 Pa (n50) was 6.1 h−1 for single-family dwellings and 7.1 h−1 for multi-family housing. Nevertheless, great dispersion of results and extreme values were found. In addition, the influence of several construction characteristics on permeability results was assessed.

Several studies on indoor air quality (IAQ) and sick building syndromes have been completed over the last decade, especially in cold countries. Efforts to make homes airtight to improve energy efficiency have created buildings with low ventilation rates, resulting in the build-up of indoor pollutants to harmful levels that would be otherwise unacceptable outdoors. This paper analyzed the infiltration rates, indoor temperatures, and variations in CO2, 2.5 m particulate matter (PM2.5), and total volatile organic compound (TVOC) concentrations over the fall of 2021 in several homes in New England, USA. A relationship between outdoor and indoor conditions and ventilation strategies has been set using the results from blower door tests and actual indoor air quality data. Although all case studies lacked mechanical ventilation devices, such as those required by ASHRAE Standard 62.2, natural ventilation and air leakage have been enough to keep VOCs and PM2.5 concentration levels at acceptable values most of the studied time. However, results revealed that 25% of a specific timeframe, the occupants have been exposed to concentration levels of CO2 above 1000 parts per million (ppm), which are considered potentially hazardous conditions.