Changes in exposure to PM2.5 in English dwellings: an unintended consequence of energy efficient refurbishment of the housing stock

UK legislation will result in energy efficiency gains through increased insulation, and airtightness in UK housing in the coming decades. This limited-focus policy approach has led to an array of possible unintended consequences, including likely changes in Indoor Air Quality (IAQ) and exposure profiles for airborne pollutants such as PM2.5. Quantification of any changes in indoor concentrations of PM2.5 is needed due to known impacts on population health. This thesis seeks to address whether the introduction of energy efficiency and ventilation strategies will lead to negative unintended consequences by increasing PM2.5 concentrations in English dwellings, or provide health co-benefits by reducing indoor PM2.5; what factors influence such concentrations and whether their contribution can be quantified? Its geographical focus is the English housing stock commencing with London, comparing London with another location (Milton Keynes) and finally extending to the whole English stock. It considers possible differences in exposure as experienced by different income groups and tenures. It investigates the range of interacting factors that contribute to indoor PM2.5 exposures including for example; external meteorological conditions/pollutant concentrations; location; building characteristics; ventilation type; indoor sources; occupant income and behaviour. Such complexity requires a modelling approach. Building archetypes representative of English dwellings and validated ventilation and indoor pollutant simulation techniques are used to model both current and future changes in indoor PM2.5 exposures. Highlights of the research findings include (1) The application of purpose provided ventilation and removal of indoor generated PM2.5 at source are critical to the overall reduction of indoor exposure in most cases; (2) Increasing envelope airtightness alone reduces ventilation heat loss, assisting CO2 reduction targets whilst also reducing ingress of external PM2.5, but substantially increases indoor sourced PM2.5 concentrations with possible overall negative health consequences; (3) Building characteristics, location, income level and occupant behaviour influence individual exposure where energy efficiency measures are implemented; (4) Households below the low income threshold are more likely to experience greater indoor PM2.5 concentrations, although further monitoring research is needed to confirm/refute this; (5) The models constructed for this study have a possible wider applicability for other airborne pollutants, locations, and building stocks