Uncertainty and sensitivity analyses applied to a dynamic simulation of the carbon dioxide concentration in a detached house

Abstract

This paper aims to study the variability of indoor CO 2 concentration due to occupant behaviour and physical parameter uncertainties. A case study, conducted in a mechanically ventilated detached house, is presented with an uncertainty and sensitivity analysis (Monte Carlo method with a Latin hypercube sampling). Uncertainties related to occupant behaviour are described by combining four types of scenarios: occupation, generation of CO 2 per person, indoor doors, and outdoor windows' openings. The uncertainty analysis showed that despite an acceptable average room CO 2 concentration, large variations, due to input parameter uncertainties, are observed in CO 2 instantaneous concentrations. Moreover, during occupied periods, average value is relatively important (higher than 1300 ppm). Occupants spent around 30% of the time at CO 2 concentrations over 1500 ppm. Large output uncertainties are reached on the cumulative CO 2 concentration and time fraction spent over 1500 ppm. The sensitivity analysis highlights the strong influence of the parameters related to bedrooms (number of occupants, night generation of CO 2) and of the kitchen extracted airflow rate. It also shows that low-level air change rates in bedrooms are mainly caused by an incorrect air distribution in the building. Potential solutions to reduce both concentrations and uncertainties are discussed.

Keeping Doors Closed as One Reason for Fatigue in Teenagers—A Case Study

“…In our study, the average concentration during the night was similar in both bedrooms, at 1077 ppm (teenager) and 1103 ppm (child), which is comparable with the average CO 2 concentration in unoccupied bedrooms (999 ppm and 1236 ppm in South and North bedrooms, respectively) as reported by Bouvier et al [25]. In occupied bedrooms, the authors in [25] reported higher (1585 ppm and 1760 ppm in South and North bedrooms, respectively) than our average concentration of CO 2 , which was 766 ppm and 860 ppm with open doors and 1402 ppm and 1337 ppm with closed doors, in the teenager's and the child's bedroom, respectively (Figure 3). However, it is similar to the average CO 2 concentration of 716 ppm measured in 13 bedrooms located in Athens' residences [39].…”

“…When an individual does not get enough sleep to feel awake and alert, they begin to experience symptoms of sleep deprivation such as yawning, irritability, fatigue, inability to concentrate, moodiness, forgetfulness, lack of motivation, depression, and poor perspective on life [3]. In our study, the average concentration during the night was similar in both bedrooms, at 1077 ppm (teenager) and 1103 ppm (child), which is comparable with the average CO 2 concentration in unoccupied bedrooms (999 ppm and 1236 ppm in South and North bedrooms, respectively) as reported by Bouvier et al [25]. In occupied bedrooms, the authors in [25] reported higher (1585 ppm and 1760 ppm in South and North bedrooms, respectively) than our average concentration of CO 2 , which was 766 ppm and 860 ppm with open doors and 1402 ppm and 1337 ppm with closed doors, in the teenager's and the child's bedroom, respectively (Figure 3).…”

“…During the research with opened doors, a high IEQ prevailed during 51% of the night in the teenager's bedroom, and during 26% of the night in the younger girl's bedroom. In comparison, the authors in [25] reported that time spent by an occupant in a CO 2 concentration over 1500 ppm in a mechanically ventilated detached house was approximately 30% of an entire day; thus, the IEQ in researched bedrooms could be satisfying with the door open; however, only the younger girl evaluated sleep satisfaction as high (16%). The subjective assessment of sleep satisfaction points to a lower IEQ in the case of the older girl's bedroom, which can be supported by a greater CO 2 concentration range (Figure 2) in the teenager's bedroom.…”

“…The IAQ gets worse during the winter season when the desire for thermal comfort and acceptable IAQ are in conflict. For the characterization of IAQ by measuring CO 2 concentration, several indicators and criteria can be used [25]. We selected the average CO 2 concentration and a time fraction over a limit of ∆CO 2 values spent during the night according to the PN-EN 16798 standards [20,21].…”

“…Design ∆CO 2 concentration for bedrooms (ppm above outdoors) are within the limits of ≤380 ppm (IEQ I ), 380-550 ppm (IEQ II ), 550-950 ppm (IEQ III ), and ≥950 ppm (IEQ IV ) corresponding to high (I), medium (II), moderate (III), and low (IV) indoor environment quality, respectively. IEQ evaluation based on CO 2 concentration and possible effects on occupants comfort has been examined [11,[22][23][24][25][26][27]. Polish research on CO 2 levels and possible occupant fatigue includes a few publications [9,[28][29][30][31]; however, no research regarding IEQ in the bedrooms of Polish children and teenagers have been performed.…”