At a time when the UK government has its sights on zero-carbon housing, in part achieved by tightly sealed envelopes and mechanical heat recovery ventilation (MHRV), the issue of indoor air quality (IAQ) and its implications for health has moved up the agenda; this in parallel with anxiety about the rising energy consumed by appliances, which is offsetting savings on space heating, water heating and lighting. In this context, this paper reports particular findings of a 2008-2011 EPSRC-funded research project: Environmental Assessment of Domestic Laundering, which relate to passive indoor drying (PID). To assess PID impacts, the study draws on monitored data from 22 case studies out of a wider survey of 100 dwellings in Glasgow, including laboratory analysis of air samples, and enhanced parametric dynamic moisture modelling. The evidence indicates that PID is a serious concern in terms of IAQ – firstly, apparent association of PID with high concentrations of mould spores, taking due account of confounding variables; secondly, moisture levels likely to boost dust mite populations; thirdly, potentially harmful chemicals in fabric conditioners, in particular PID linked to the concentration of acetaldehyde, a water-soluble volatile organic compound (VOC). The implication of PID for increased energy consumption is also addressed briefly, a broad-brush comparison being made with tumble-drying in this regard. A further moisture addition associated with domestic laundering is steam ironing, which, like PID, occurs in a context of other moisture sources and typically poor ventilation regimes (air too moist and CO2 too high). The paper concludes with outline recommendations for reformative building standards and design guidance, the aim to prevent PID moisture diffusion within habitable rooms by linking ‘quarantined’ drying spaces to dependable ventilation supply and exhaust systems