On Monday, December 3, 2018, Gaëlle VOISIN, a doctoral student in energy and process engineering at the Laboratory for Optimization of Design and Environmental Engineering (LCOIE), will defend her thesis entitled "Towards better consideration of indoor air quality and health in low-energy individual dwellings: Development of a performance-based approach to ventilation."
The defense will take place at 1:30 p.m. in the amphitheater of Building B2 at Polytech Annecy-Chambéry on the Bourget-du-Lac campus.
Thesis summary
Future regulations scheduled for 2020 will incorporate the concept of overall building performance, including indoor air quality (IAQ). In the field of energy, performance-based approaches have been developed to verify that buildings comply with maximum energy consumption requirements at the design stage. However, in the field of ventilation, regulations are generally based on prescriptive approaches, setting ventilation flow rates. This thesis therefore aims to develop a performance-based approach to ensure, from the design stage, that ventilation avoids any risk to the health of occupants. Furthermore, with the widespread adoption of nearly zero-energy buildings, air permeability is now increasingly being incorporated into thermal regulations in Europe. As performance evaluation often focuses on energy efficiency and rarely on IAQ, the impact of the presence of several zones, interconnected by air permeability defects in interior partitions (interior permeability), combined with non-uniform envelope permeability, is an issue that has rarely been studied and is addressed in this thesis. To address this issue, a unique campaign to measure air permeability distributions in 23 houses was used to develop a database. Analysis of this database reveals that interior permeability is significant when there is a gap between the door and the frame, and that the type of structure (light/heavy) has a considerable impact. At the end of this work, we proposed input data for multizone models on these air permeability distributions. Next, the impacts of these detailed distributions on IAQ were quantified in a case study modeling CO2, humidity, and formaldehyde in a low-energy house. The house is equipped with either single-flow (SF) or dual-flow (OF) ventilation. Significant impacts were identified. To evaluate IAQ, it is therefore necessary to model the air permeability of the envelope and interior in detail. Following extensive bibliographic research, combined with the additional analyses presented above, we were able to propose a performance-based approach to ventilation for use in a regulatory study at the design stage. We proposed five IAQ indicators to be taken into account, including CO2, formaldehyde, and PM2.5 doses, and two humidity indicators relating to the assessment of condensation risk and occupant health. We also proposed occupancy and pollutant emission scenarios to be taken into account. Finally, we described the type of multizone model to be implemented, the physical models and associated assumptions, and the boundary conditions to be used. We wanted to test this approach by applying it to a low-energy house as a case study. We therefore assumed that we were at the design stage and had to comply with hypothetical regulations setting IAQ performance targets. We thus demonstrated how such an approach would enable key choices to be made at the design stage, such as the type of structure (in view of its impact on permeability distributions), the type of ventilation system, and the level of indoor pollution (in relation to the choice of labels or labeling, for example), in terms of their impact on IAQ. In our case study, only OF ventilation combined with low or medium formaldehyde emissions allows IAQ targets to be met. We also showed that such an approach would be useful at the design stage to better size the distribution of air inlets or extraction vents, or even ventilation rates, in order to achieve OAI targets.