{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T15:33:20Z","timestamp":1768836800746,"version":"3.49.0"},"reference-count":65,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2020,3,12]],"date-time":"2020-03-12T00:00:00Z","timestamp":1583971200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["PD\/BD\/135162\/2017"],"award-info":[{"award-number":["PD\/BD\/135162\/2017"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Buildings"],"abstract":"<jats:p>Southern European countries have milder climatic conditions that differ from their colder northern counterparts, which greatly influence indoor ventilation strategies. The relation between a building\u2019s airtightness and the air change rates remains a topic to be fully tackled in these countries, since natural ventilation is very frequent. In this work, the ventilation and airtightness of a case study were analyzed in-depth to support a discussion on this topic. CO2 concentration decay and blower-door measurements were used to characterize the infiltration and ventilation conditions of the case study. The case study represents a common Portuguese situation, with highly permeable envelopes, combined with highly variable air change rates. Transient simulations were carried out for the comparison of scenarios where different configurations of possible air paths were analyzed. The simulations included both natural and mechanical ventilation scenarios. An air sweeping effect from bedroom to bathroom only occurred when the mechanical extraction ventilation (MEV) was on. Different air leakage path configurations resulted in substantial offsets, up to 63%, of the air change rate (ACH) due to natural occurring forces. The results confirmed that the relation between airtightness and air change rates should be carefully analyzed in southern European countries, as indoor air quality, comfort of occupants, and energy efficiency are highly influenced by the considered variables.<\/jats:p>","DOI":"10.3390\/buildings10030055","type":"journal-article","created":{"date-parts":[[2020,3,12]],"date-time":"2020-03-12T12:22:51Z","timestamp":1584015771000},"page":"55","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["The Impacts of Air Leakage Paths and Airtightness Levels on Air Change Rates"],"prefix":"10.3390","volume":"10","author":[{"given":"Vitor E. M.","family":"Cardoso","sequence":"first","affiliation":[{"name":"Institute of R&amp;D in Structures and Construction (CONSTRUCT), Laboratory of Building Physics (LFC), Faculdade de Engenharia (FEUP), Universidade do Porto, Rua Dr. Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3456-0068","authenticated-orcid":false,"given":"Pedro F.","family":"Pereira","sequence":"additional","affiliation":[{"name":"Institute of R&amp;D in Structures and Construction (CONSTRUCT), Laboratory of Building Physics (LFC), Faculdade de Engenharia (FEUP), Universidade do Porto, Rua Dr. Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"given":"Nuno M. M.","family":"Ramos","sequence":"additional","affiliation":[{"name":"Institute of R&amp;D in Structures and Construction (CONSTRUCT), Laboratory of Building Physics (LFC), Faculdade de Engenharia (FEUP), Universidade do Porto, Rua Dr. Roberto Frias s\/n, 4200-465 Porto, Portugal"}]},{"given":"Ricardo M. S. F.","family":"Almeida","sequence":"additional","affiliation":[{"name":"Institute of R&amp;D in Structures and Construction (CONSTRUCT), Laboratory of Building Physics (LFC), Faculdade de Engenharia (FEUP), Universidade do Porto, Rua Dr. Roberto Frias s\/n, 4200-465 Porto, Portugal"},{"name":"Polytechnic Institute of Viseu, School of Technology and Management, Department of Civil Engineering, Campus Polit\u00e9cnico de Repeses, 3504-510 Viseu, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2020,3,12]]},"reference":[{"key":"ref_1","unstructured":"European Comission (2019, November 07). Heating and Cooling. Available online: https:\/\/ec.europa.eu\/energy\/en\/topics\/energy-efficiency\/heating-and-cooling."},{"key":"ref_2","unstructured":"European Comission (2016). 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