Energy saving measures with reduced outdoor air change rates may lead to critical indoor air contaminant concentrations. Emission characteristics of construction materials and products play an important role. Therefore a project has been set up at EMPA to investigate emission characteristics of such materials using test chambers.

Ventilation efficiency may be defined as the capability of a given ventilation system to achieve the best balance between indoor air quality and energy conservation requirements:

The paper reviews some problems of theory and practice of energy conservation in buildings. The necessity for a policy of energy