Damp and overcrowded housing has significant adverse health effects, Poor quality housing disproportionately impact on low-income individuals and children. A significant number of homes in New Zealand are damp, cold and poorly insulated, and crowded (too many occupants relative to the size of the house). These factors give rise to a particular indoor air quality (IAQ) problem: a combination of low temperature, high relative humidity, and high allergen and pathogen content of the air.