The IEA EBC Annex 68 project on "Indoor Air Quality Design and Control in Low Energy Residential Buildings" has been recently completed. The project considered indoor air pollution loads in dwellings, particularly how such pollutants are emitted in dependency of the hygrothermal conditions: temperature, moisture and air flows. Thus, a proper understanding of the mutual interactions between hygrothermal conditions and pollutants was needed to obtain optimal paradigms for demand-controlled ventilation. The project adopted a similarity approach for modelling the transports of moisture and volatile organic compounds (VOCs) in materials, and thereby it was possible to provide a comprehensive set of data and tools whereby the indoor atmospheric conditions of buildings can be optimized, e.g. with respect to the need for ventilation. The paper explains the experimental and modelling approach and presents a summary of the results.