text: Weatherization generally does not cause indoor air quality problems by adding new pollutants to the air. (There are a few exceptions, such as caulking, that can sometimes emit pollutants.) However, measures such as installing storm windows, weather stripping, caulking, and blown-in wall insulation can reduce the amount of outdoor air infiltrating into a home. Consequently, after weatherization, concentrations of indoor air pollutants from sources inside the home can increase.
  Weatherization may have a negative impact on indoor air quality, if done improperly, exacerbating respiratory conditions especially among occupants with pre-existing respiratory illnesses. This may occur because of a drastic decrease in air exchange rate in the home, introduction of new chemicals, and poor management of indoor moisture due to a poorly performed weatherization work. Low air exchange rates may lead to higher concentrations of pollutants in the air when ventilation is not sufficiently addressed during weatherization work. However, the situation may be different in case of a house situated in an area with high outdoor air pollution levels such as in close proximity (<200 m) from a busy major road. In such a scenario, a more airtight building envelope can actually offer protection against infiltration of outdoor air pollution. The same is true for the protection offered by tighter building envelopes during wildfire events that cause elevated levels of outdoor air pollution.