In low energy dwellings the ventilation heat losses are significant. Reduction of these heat losses can be achieved by introducing demand controlled ventilation i.e. ventilation rates are set below normal level when rooms are no longer occupied. This paper outlines preliminary results on energy conservation and health effects in relation to demand controlled ventilation in a low-energy house. Simulations with the dynamic building performance simulation model TRNSYS 14.2 were run to evaluate the extra conservation of natural gas for space heating of a dwelling equipped with demand controlled ventilation system. To simulate the ventilation demands, the simulation program used typical Dutch occupation schedules of a family with four members. Preliminary results indicate an extra energy conservation of 15-20% with regard to the reference situation. Indoor climate parameters such as air tap water temperature, relative humidity, dust and air exchange rate were adopted as indicators of human health risk. Experimental results indicate an elevated risk on overheating during the summer, odour nuisance in the sleeping room and kitchen, irritation of mucous membranes, including allergy, and Legionnaires disease.@en