This work looks into the indoor air quality at homes in Mexico City, and the use of the PassivHaus building certification as a way to improve it. For this purpose, monitoring in some homes in Mexico City is being carried out. Low-energy homes often address airtightness as a measurement to assure thermal comfort with the lowest energy consumption possible. But, it is known that air other problems might arise by addressing airtightness; such as ventilation, air pollution and mould. This paper focuses on IAQ and describes the possible implications of IAQ in low-energy homes in Mexico.