Deteriorated indoor climate is commonly related to increases in sick building syndrome symptoms, respiratory illnesses, sick leave, and losses in productivity. The cost of deteriorated indoor climate for the society is high. Building-level calculations have also shown that many measures taken to improve indoor air quality and climate are cost-effective when the potential monetary savings resulting from an improved indoor climate are included as benefits gained. --There is a strong need for quantitative information relating IEQ conditions or related building characteristics to human response and linking these responses to costs so that the models can be broadly applied. Professor Seppanen will present some models developed at LBNL and in Finland linking IEQ, building factors, health and performance.