This review assesses the current state of knowledge on indoor air quality in energy efficient,
airtight houses in the UK and elsewhere in the world. It summarises the characteristics of homes
built to Levels 4, 5 and 6 homes of the Code for Sustainable Homes, and discusses the
relationship between indoor air quality and occupant wellbeing. Research in the UK, Europe and the rest of the world into indoor air quality and other factors which may impact on occupant wellbeing is reviewed. This is followed by a review of current research and state of the art for ventilation performance in dwellings and of construction and ventilation provision in highly energy efficient homes.