More than ever before, the COVID-19 crisis and the need to spend longer periods of time in our places of residence, have highlighted the need to improve indoor air quality (IAQ) and ventilation to reduce the risks of airborne virus transmission. Added to the need to progressively improve the energy performance of our buildings to achieve carbon neutrality is this completely contrary new requirement, which forces reconsidering the ventilation issue, its standards, and technological solutions to improve IAQ and limit the risks of contagion inside our homes, without losing sight of the goals that climate change imposes on us. Chile is seeking strategies to generate sustainable, energy-efficient, and comfortable housing, which must be reconsidered in light of Covid-19. Greater permanence inside the home revealed the precariousness of the lifestyles the most vulnerable families face; sometimes exposing them to environments that are risky for their health. The objective of this research was to estimate the impact of Covid-19 on CO2 indoor air concentrations, as a result of the intensity of use (occupation) of the home, considering envelopes with different levels of airtightness. Using an experimental methodology, based on simulations with the DesignBuilder software, the CO2 concentrations of four types of social housing, located in the commune of Coronel, Biobío, Chile, were quantified. The results showed that confinement increased CO2 levels by 16.4%, while the change from the original condition of the envelope to more airtight levels generated an increase of more than 83% in normal use and 97% for periods of confinement.