Carbon Dioxide Concentrations and Humidity Levels Measured in Belgian Standard and Low Energy Dwellings with Common Ventilation Strategies

One of the most commonly used strategies to reduce the heating demand in low energy buildings is reducing the leakage level of the building envelope. Dedicated ventilation systems are then installed to compensate for the reduced air change rate in an energy efficient way. Most occupants, however, operate their ventilation system at very low flow rates. Together with the emission of bio-effluents, linked to the presence of the occupants, moisture production related to household activities is one of the most important sources of indoor air pollution in dwellings. These activities are usually concentrated in bathrooms and kitchens, while occupancy is usually situated in the living rooms and bedrooms. Therefore, most ventilation standards position supply vents in the living spaces and exhaust vents in kitchens and bathrooms. Most literature focuses on exploring the merits of new ventilation concepts or the understanding of airflow phenomena, but there is a lack of information about the real life performance of the basic concepts in dwellings. This paper presents the results from carbon dioxide monitoring in the living spaces, combined with humidity measurements in the exhaust spaces of 36 old, 39 standard and 39 low energy dwellings in Belgium. The results show that the risk of exposure to high carbon dioxide concentrations in the bedroom is about 6 times higher than that in the living room due to the long time spent there. It also provides a good overview of what kind of humidity levels are achieved in practice, and how these relate to the design intentions.