Uncertainty of IAQ and energy performance schemes for residential smart ventilation

In high-efficient residential buildings, energy use due to ventilation can reach 60% of the total building. Smart-ventilation systems with variable airflows adapting to the need of buildings and occupants can increase the energy performance of the building and at the same time improve or maintain IAQ. They are also considered as a huge opportunity for new and existing residential buildings. 
In some countries (like France and Belgium), smart ventilation has been widely used for dozen of years and has become reference strategies. In some other countries, smart ventilation strategies are quite recent or only partially implanted (only in some countries like Belgium, France, The Netherlands, Ireland, Spain…). Their IAQ and energy benefits need to be quantified through performance assessment schemes, still under development, notably in the framework of the IEA-EBC Annex 86. In this article, we propose to quantify the uncertainty of a new recent performance assessment method using RBD-FAST sensitivity analysis. We quantified the variations of impacts of input data such as: the pollutant emissions scenarios - moisture, formaldehyde and particle matter PM_2.5 -, model input parameters and ventilation strategies.  
For this sensitivity analysis, five ventilation systems were studied on a French low energy house: 2 with constant airflows, 1 humidity-based exhaust-only smart ventilation and 2 humidity+CO₂ based smart ventilation. The sensitivity indices analysis shows that occupant bio-effluent, formaldehyde and PM_2.5 emissions rates are responsible for 11% to 87% of the uncertainty for the IAQ performance indicators. The PM_2.5 deposition velocity parameter is responsible of 50% of the uncertainty on the PM_2.5 indicator, which was an unknown impact until now and pushes toward more research in order to better characterize this parameter. In addition, the article highlights the energy benefits of this humidity-based ventilation, with heat losses on average 20% lower than those obtained with equivalent constant airflow ventilation. In addition, some smart ventilation strategies offer clear IAQ benefits without significantly increasing energy demand.