Seasonal Variability of Air Infiltration Rates in Buildings with Differing Airtightness

Abstract

This study investigates the seasonal variability of air infiltration rates (Ninf) in two residential buildings with differing envelope airtightness (B1: older, lower; B2: newer, higher). Ninf were quantified using the CO2 decay method in February and June 2025. Ninf were higher and more variable (B1: 0.14–0.27 h─1, avg 0.19 h─1; B2: 0.04–0.21 h─1, avg 0.10 h─1) in winter and lower (B1: 0.06–0.25 h─1, avg 0.13 h─1; B2: 0.00–0.22 h─1, avg 0.06 h─1) in summer. Ninf decreased with increasing outdoor temperature, with meteorological influences more evident in the less airtight building.