RENOVAIR: Study of the evolution of airtightness, ventilation, comfort and indoor air quality in 7 energy renovation operations of social housing in France

This article follows a first publication presented at the AIVC2022 conference (Handtschoewercker, 2022), with the preliminary results of the RENOVAIR project, that studies the impact of energy renovation works on social housing on the comfort and health of occupants when no requirements are given on IAQ, ventilation and airtightness performances. 
In the frame of the eco-conditioned financial aid supported to the ERDF 2017-2022 operational program for the energy renovation of social housing building stocks, the eligibility conditions for financial aid concern requirements on energy consumption, thermal insulation performance and the energy efficiency of heating systems. Yet, the current specifications of this program do not condition any financial assistance on performance criteria relating to indoor air quality (IAQ), ventilation and airtightness of the building envelope. Thus, the RENOVAIR project studied the evolution of these performances, knowing that it is commonly admitted that these issues are essential for achieving comfortable low energy buildings.  
RENOVAIR is based on 7 candidate operations for the ERDF program for the energy renovation of social housing in the Nouvelle-Aquitaine region (southwest of France). In this 3-year work, we sought to characterize the performances of IAQ, comfort, airtightness and ventilation, before and after the renovation work, through in situ measurement campaigns on 21 housing units, in order to assess the importance of such requirements in the implementation of public decarbonization policies. 
This article presents the final results from the three measurement campaigns: before works, after works and one year after works. On each of the 7 pilot sites, measurements were carried out on 3 dwellings in order to characterize the evolution of performance following the energy renovation work: 

1. Through air flowrates and pressure measurements, we determined whether the ventilation systems allowed sufficient air renewal in the renovated housing for each campaign.
2. Airtightness measurements carried out according to the NF EN ISO 9972 standard highlighted the location of air leaks in homes during each of our visits and their evolution after each step.
3. Dynamic measurements of temperature, relative humidity and CO2 and passive VOC measurements characterized the impact of the work on the IAQ in each dwelling.
4. The thermal comfort of the occupants was determined by commercial low-cost sensors in each accommodation for two weeks during the winter period

​In light of the results of our work, which reveal in some cases a deterioration of performance, we discuss the need of explicit requirements regarding IAQ, ventilation and airtightness with the objective to reach low energy consumption renovated buildings. We also discuss the efficiency of the retrofits according to the associated cost, the energy gains and the discomfort problems that can arise.