Impact of Positive Pressure Ventilation Systems on Indoor Air Quality in Residential Settings

Abstract

Effective ventilation is a key requirement in residential buildings to achieve healthy indoor air quality (IAQ) through the introduction of fresh air. Mechanical ventilation (MV) systems are designed to meet IAQ objectives by delivering regular air exchange and dilution of stale air. Positive pressure ventilation (PPV) systems commonly source air from the roof cavity and distribute it throughout the indoor environment. This study evaluated the effects of PPV systems on IAQ in 10 single-family dwellings over a nine-month period across three seasons (winter, spring and summer) and including pre-and post-installation monitoring. Regular measurements of IAQ parameters including PM<inf>2.5</inf> PM<inf>10</inf>, radon, fungal DNA, and heavy metals were collected from bedrooms, living areas, roof spaces and outdoors. Mean indoor concentrations of PM<inf>2.5</inf> and PM<inf>10</inf> each decreased by 44 % following PPV installation. Outdoor levels of PM<inf>2.5</inf> and PM<inf>10</inf> increased over the same period, by 41 % and 37 %, respectively. Reductions in mean indoor concentrations were also observed for radon (53 %) and fungal DNA (64 %). Indoor concentrations of heavy metals also decreased, with chromium, copper, lead, nickel, and zinc decreasing by 28 % on average, while arsenic and cadmium were generally below detection limits. Indoor PM<inf>2.5</inf> concentrations were 31 % higher than roof space concentrations, and weakly correlated (Spearman's coefficient, r<inf>s</inf> = 0.12), suggesting limited influence from the roof cavity. Temperatures in the roof space were 7.1 °C lower, on average, than indoor temperatures. Analysis suggests that a higher temperature differential between roof and indoors is associated with higher levels of energy use, particularly at differentials above 4 °C.