Long-term impacts of energy retrofits on indoor air quality and climate – Follow-up results of a sample of Finnish apartment buildings

Energy retrofits can have an impact on indoor air quality and climate, particularly on temperature, humidity, and concentrations of air pollutants. Both positive and negative impacts have been identified, usually based on measurements taken quite soon (up to about one year) after the retrofits. We studied the long-term (about seven years) impacts of energy retrofits on indoor thermal conditions, ventilation rates, and CO₂ and radon concentrations during heating season in 13 Finnish apartment buildings (42 apartments) along with the occupants’ self-reported satisfaction with IAQ. High indoor temperatures and low RH were recorded in all the measurements. There were no significant changes in the night-time average CO₂ concentration (less than 700 ppm) and momentary air exchange rates (0.3–0.35 (dm³/s)/ m²) between the measurements. There was a decreasing trend in radon concentration. Seven years after the retrofit, the average radon concentration was 23 % lower than before the retrofit. Concentrations above 100 Bq/m³ were also less frequent after the retrofitting. According to the occupant questionnaire, the respondents were significantly more satisfied with IAQ about one year after the retrofits. About 7 years after the retrofit, they still appeared to be more satisfied with IAQ than before the retrofits.