A rapid review of the impact of increasing airtightness on indoor air quality

Sealing the gaps in a house, or increasing airtightness, is a common approach to reduce energy consumption, as well as make the house more comfortable to live in. However, people need a certain amount of fresh air in their homes to maintain air quality, and concerns have been raised that increased airtightness may have the unintended consequence of reduced indoor air quality (IAQ). This rapid review identified 20 studies that investigated the impact of increasing airtightness on indoor air quality. These studies covered a broad range of locations, climates and building types. Indoor air quality parameters investigated included CO2, PM2.5, formaldehyde, VOC, NO2, relative humidity, mould issues, carbon monoxide (CO) and radon. Based on the studies reviewed, there was limited evidence to identify direct correlations between increasing airtightness and indoor air quality in general. A negative correlation with CO2 concentration was found from the studies, with concentrations increasing with a decrease in the air tightness levels. There was evidence of a negative correlation for VOC and formaldehyde, although a number of studies found no clear relationship for these parameters and further studies would be required to understand this impact. A positive correlation was found between the air exchange rate and PM2.5 and NO2 concentrations in areas where there are high outdoor levels. In these cases, increasing airtightness was found to reduce the infiltration of outdoor contaminants. There were no direct correlations identified for mould issues, radon or CO, or for PM2.5 or NO2 in areas with average outdoor levels.