Conference Agenda

Air Change Rate (ACR) is a key parameter influencing building energy performance and the indoor environment. An accurate estimate of ACR can inform building envelope retrofit decisions to improve airtightness and Indoor Air Quality (IAQ). However, windflow and interior-exterior temperature differences make the accurate measurement of the ACR challenging. Conventional testing approaches present certain drawbacks limiting their applicability in various buildings. We studied the advantages and disadvantages of various methods including a steady-state approach where the CO2 level is relatively constant, a decay method, a transient CO2 mass balance method, and air moisture balance method for estimating ACRs. These methods were compared with measurements in two single-family attached residential apartments in which indoor environmental data (CO2, temperature, and humidity) and motion data were collected for pre- and post-retrofit conditions to assess the effectiveness of an integrated retrofit solution on the IAQ and energy performance. The study also compared ACRs in two bedrooms and the whole apartment unit, revealing significant spatial differences when the bedroom doors were closed. The results also revealed much higher ACRs during the occupied period compared to the unoccupied period for the pre-retrofit conditions where no mechanical ventilation was available due to opening of windows and doors by occupants as detected by motion sensors. For post-retrofit, more stable ventilation rates were achieved by the energy recovery ventilator. The findings for an end apartment unit and a middle apartment unit showed a 56% and 43% reduction in ACRs in the living room after the retrofit, respectively. This study contributes to a more accurate assessment of the post-retrofit condition relative to a baseline using the ACR metric, considering the important impact of the occupants and their preferences for prioritizing IAQ or thermal comfort.