The study presented in this article concerns the numerical simulation of airflows and occupational exposure to household contaminants. A finite volume code (CFD) is used to simulate a single-family house with several ventilation, heating, and climatic conditions. The concentration and occupational exposure levels of household contaminants CO2, CO, HCHO, NO2, and water vapour, all from human metabolism, along with those from gas cooking and smoking, are evaluated over a day for a generic occupational schedule of four family members. The ventilation types incorporated bimodal, relative humidity controlled and balanced systems, coupled with either room convectors or a combination of a heated floor and room convectors. Winter and summer climates provided a wide range of outdoor conditions, and also isolated the effects of the heating systems. Comparisons between the combinations of systems are presented, based upon the breathed concentrations of each family member throughout a normal day. The occupational exposures of the family are also assessed.