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.

In the current global scenario, there exists a significant surge in the pursuit of retrofitting endeavors within residential infrastructure, driven by the essential need to mitigate carbon emissions at a national level. A critical aspect within this retrofitting context involves substituting conventional heating systems with the electrification of heat, particularly through the adoption of heat pump technologies. The primary objective of this study is to analyze the retrofitted residential built form from energy, carbon, and thermal comfort perspectives, providing an overview of the renovated built form. Moreover, particular emphasis will be placed on the operational phase, with a focus on improving thermal comfort and reducing carbon emissions based on monitored indoor parameters. In this study, a deeply retrofitted dwelling from the pre-1978 period, upgraded to achieve an A2 BER rating, is examined. The annual primary energy consumption in the post-retrofitted house is 49.5 kWh/178 MJ/m2/annually, while in the pre-retrofitted house, the primary energy consumption is 83.8 kWh/301.7 MJ/m2/annually, including electricity and gas. The pre- and post-retrofitted operational carbon footprints are identified as approximately 15.9 kgCO2eq./m2/annually and 6.4 kgCO2eq./m2/annually. Furthermore, in the post-retrofitted building, the thermal comfort level is determined by the PMV index, which ranges from 0 to -1.5. Overall, this analysis provides a comprehensive view of the post-retrofitted house, encompassing energy, carbon, cost, and thermal comfort.

In building energy renovation, the notion of payback time is often presented as the only goal i.e. it is important to demonstrate that energy savings can rapidly reimburse the investments made to generate them. However, the notion of comfort gain, as well as the potential benefits in terms of health, are also important and should be accounted for. This paper presents the results of the French research project Smart-Réno-IEQ (2019-2021) that aimed at analyzing the impacts of energy retrofits on indoor thermal and air quality of single-family houses. Based on an analysis of the existing building stock (construction year, envelope composition, heating system, infiltration and ventilation rates…) and retrofitting actions done in recent years (window replacement, increasing the wall/roof insulation, changing the heating/ventilation systems…), a set of single and multiple renovation actions have been defined to assess the performance of the renovation in terms of thermal comfort and Indoor Air Quality (IAQ). The different configurations have been modelled accounting for heat and mass (air and pollutants) transfers in multizone houses during the whole year. A new indicator, based on existing indices, has been defined to evaluate both thermal comfort and IAQ for each season, year and overall to assess the benefits of retrofitting. Results show that effects on thermal comfort such as replacement of windows, thermal insulation of vertical walls or attics are negligible even if they are essential for energy consumption reduction. Only actions of limiting indoor sources of pollutants and upgrading ventilation have noticeable positive effects on IAQ and positive or negative ones on thermal comfort. Another finding in line with energy performance efficiency is that packages of renovation actions are always more beneficial for IAQ than isolated actions.