Adverse health effects of human exposure to outdoor Particulate Matter (PM) have been established. In this study, we investigate the effectsof improved residential regulations to reduce outdoor PM exposures indoors and associated health impacts among adult and children population inToronto and Hamilton, Canada. Using a mass balanced concentration model, time-weighted activity exposure model and epidemiological basedconcentration-response model, indoor exposures to outdoor PM and various morbidity and mortality outcomes were estimated for variousresidential building scenarios. The study demonstrated that retrofitting residential buildings to comply with National Building Code (NBC)regulations can provide protection in time-weighted PM2.5 exposure among children (mean reduction: 20%) and adults (mean reduction: 18%) inthe two cities. The reductions in time weighted exposures were more significant if all residential buildings in the two cities comply with the R2000standards (children: 43%; adult: 38%). The variations in exposure reduction are dependent on seasons with winter having a larger impact (34%versus 28%) compared to summer due to the greater time spent indoors. Estimated prevented non-accidental mortality impacts associated withthese exposure reductions in Toronto and Hamilton are 10 and 59 if residential buildings adopt minimum NBC regulations and 21 and 124 ifresidential buildings adopt R2000 standard. Other morbidity outcomes such as chronic bronchitis, asthma, hospital admission due to respiratoryillness, restricted activity days and work loss days can be avoided with improved residential regulations. Installing efficient air filtration is the maindeterminant for PM exposure and health outcomes reductions. This study showed that residential building regulations targeting to reduce outdoorPM exposure indoors can achieve health benefits at the population level.