This report provides information and advice to policy and decision makers, researchers, architects, designers, and manufacturers on (i) strategies for achieving a satisfactory balance between good indoor air quality (IAQ) and the rational use of energy, (ii) guidelines on the use of energy in buildings and IAQ currently available, (iii) significant trends in the building sector with implications for IAQ and energy use and (iv) current research concerns. The report discusses the relationships and potential conflicts between IAQ and the efficient use of energy in buildings and related factors such as the influence of occupancy and occupant activities, energy use and sustainability, indoor air pollution and its control, and health and comfort aspects of indoor air quality and climate. The influence of climatic conditions and their variations across Europe on IAQ and energy use, socio-economic costs of poor IAQ and its relation to the use of energy and trends for the future in the building sector are also briefly addressed. Current research concerns in the field of IAQ and energy use in buildings are highlighted and gaps in knowledge and research needs are identified. Key elements of a strategy by which designers, engineers, manufacturers and other decision makers can achieve a good balance between energy use in buildings and indoor air quality (IAQ) are proposed. Following the recommended procedure will reduce the risk of poor IAQ and waste of energy.