Indoor air quality and comfort in seven newly built, energy-efficient houses in France

A field survey was carried out in seven newly built energy-efficient houses in France. Several indoor air-quality indicators (total volatile organic compounds, volatile organic compounds, aldehydes, carbon monoxide, particulate matter less than 2.5 μm in diameter (PM2.5) and radon) and indoor environmental parameters (carbon dioxide, temperature, relative humidity and noise) were measured before and during the houses' first year of occupancy. The air exchange per hour (ACH) and air exhaust rate were measured simultaneously, and the perceptions of the occupants were evaluated with a questionnaire. The results show that the levels of aromatic hydrocarbons, terpenes, alkanes and aldehydes were higher before occupancy than during occupancy, whereas the opposite trend was observed for PM2.5. During occupation, the concentrations of acetaldehyde, alpha-pinene, ethylbenzene, limonene, styrene, toluene and xylenes decrease, most likely because of the decrease in emissions sources from houses. At the same time, the levels of benzene, formaldehyde, hexaldehyde, n-decane and n-undecane temporarily increase because of human activities. The PM2.5 levels show seasonal variation. Compared to standard French houses, the concentrations of benzene, ethylbenzene, m- and p-xylenes, PM2.5 and radon were low, whereas the CO2 and formaldehyde levels were not significantly different. In contrast, the levels of acetaldehyde, hexaldehyde, n-decane, n-undecane, oxylene and styrene were higher in these new homes, possibly because of the emissions from products and materials. Mechanical ventilation with heat-recovery systems allows for ACH levels of 0.5 h−1 or higher, making the air drier. Shortcomings of the system are also reported.