Oriented strand board (OSB) is a building material used in new Canadian residential household construction. OSB emits formaldehyde, a suspected carcinogen that may pose a health risk to residents of Canadian households. This study employs a time-averaged mass balance model and Monte Carlo simulations under quasi-steady state conditions to assess indoor concentrations of formaldehyde attributed to the presence of OSB wall sheathing within the building envelope of single-detached Canadian households. This study suggests 7.6% to 14% of the total indoor concentration of formaldehyde could be attributed to the off gassing of OSB wall sheathing during initial homeowner occupancy.