Comparison of air pressure difference, air change rates, and CO2 concentrations in apartment buildings before and after energy retrofits

Impacts of energy retrofits on air pressure differences across building envelope, air change rate (ACR), and indoor carbon dioxide (CO2) concentrations were studied. Measurements were performed before and after the retrofits of multi-family buildings during heating season in two Northern European countries: Finland and Lithuania. In the Finnish case buildings (Napartments = 128), pressure differences against outdoor were within national guideline values before the retrofits in 52% and after the retrofits in 42% of the buildings with mechanical exhaust ventilation system. The values were within the guidelines before the retrofits in 33% and after the retrofits in 20% in buildings with natural ventilation, correspondingly. In the Lithuanian case buildings (Napartments = 31), pressure differences against outdoor were within the same guideline values before the retrofits in 77% and after the retrofits in 52% of the buildings. After the retrofits, higher air pressure differences and ACR, as well as lower CO2 concentrations, were observed in Finnish buildings with mechanical ventilation. On the contrary, lower air pressure differences and ACR, as well as higher CO2 concentrations, were observed in Lithuanian buildings with natural ventilation. •In Finland○Pressure differences were usually a slightly higher after the retrofits.○Air change rates were somewhat higher after the retrofits in buildings with mechanical ventilation and about the same in buildings with natural ventilation.•In Lithuania○Pressure differences were lower after the retrofits.○In buildings with natural ventilation, ACR through ventilation outlets was about the same.