Center for the Built Environment

The dissertation thesis investigates the impact of energy renovation on the indoor environmental quality of apartment buildings. Two case studies were carried out. The first field study was performed in three pairs of residential buildings. One of the buildings in each pair has been renovated and the other was in its original state. The second field study investigated one residential building before and after its renovation. Both objective measurements and subjective evaluation using questionnaire were used. Temperature, relative humidity and the concentration of CO2, were measured in the bedrooms of the apartments in both studies. Moreover, in the second case study additional measurements of indoor air pollutants were carried out, such as nitrogen dioxide, formaldehyde and (total) volatile organic compounds. CO2 concentration was significantly higher in the renovated dwellings that reflected lower air exchange rates in the apartments in winter. The higher CO2 concentrations and lower air exchange indicated increase of formaldehyde concentrations in the apartments. Moreover, strong association was found between levels of formaldehyde and relative humidity. These observations were linked to insufficient airing out in the apartments and occupants´ lower satisfaction with perceived air quality after renovation. In a greater fraction of the apartments the occupants ventilated as frequently as before renovation and was inadequate to achieve better indoor air quality indoors. The results of the simulations confirmed that energy renovation without considering additional ventilation, which is often the common practice, may increase CO2 concentrations in the apartments. Adding standard air handling units in bedrooms, or, at the minimum, exhaust systems in kitchens and bathrooms while at the same time keeping internal doors open, may significantly improve indoor air quality in newly energy-renovated residential buildings.