Method to assess the performance of ventilation systems in dwellings considering the influence of uncertainties

Normally, the design of a ventilation system in a dwelling is based on national regulations, related design rules, building tradition and general knowledge about healthy indoor air quality, ventilation and air handling units. In practice, the actual performance of ventilation systems is determined by ventilation components, building properties, outdoor environment and occupant behavior. Unspecified items in the design rules and uncontrollable items in the design stage will bring uncertainties which may cause the actual performance deviating from the designed performance. In this research, an assessment method considering the influence of such uncertainties is proposed and developed. First, the method for defining criteria for assessing the performance of ventilation systems in houses is described. The basic idea is that the criteria should be defined based on the national ventilation regulations. Then, the process for estimating the uncertainties in four aspects (including ventilation components, building properties, outdoor environment and occupant behavior) is introduced based on the definition of 5 main uncertainty sources. The relevant parameters in each aspect and the main uncertainty sources for each parameter are figured out. A point which may be interesting is that we propose to explore the reaction of the system performance to certain occupant behavior rather than predicting the occupant behavior pattern. Later on, the uncertainty analysis techniques including uncertainty propagation technique and sensitivity analysis technique are introduced as Monte-Carlo simulation (with Latin-hypercube sampling) and Morris factorial sampling respectively. The uncertainties in ventilation components, building properties and outdoor environment are involved in both uncertainty propagation and sensitivity analysis while the occupant behavior is only analyzed via a sensitivity analysis. A pilot case study using the described method is given afterwards. The conclusions are that there is a necessity to integrate the influence of uncertainties in the assessment of ventilation systems in houses and that the introduced method could give a useful framework and approach for such assessment.