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- Estimating ventilation rates in a window-aired room using Kalman filtering and considering uncertain measurements of occupancy and CO2 concentrationPublication . Duarte, Rogério; Gomes, Maria da Glória; Rodrigues, António MoretThis paper describes a method for estimating ventilation rates in a window-aired room considering “in-use” conditions and uncertainty in occupancy (CO2 release) and in measurements of indoor air CO2 concentration. Estimates are drawn from indoor air mass conservation principles and an Extended Kalman Filter, serving as state observer. The modelling procedure is described and tested against synthetic time series generated from pseudorandom values of occupancy and ventilation rate. Additionally, data collected from a case study (a window-aired classroom) is used to illustrate how the procedure is applied and its practical interest. Test results confirm the state observer’s tracking capability and confirm its ability to reconstruct ventilation rates in the presence of sudden changes caused by window opening/ closing and intermittent occupancy. Results for the case study highlight the benefits to designers and ultimately to occupants, derived from knowledge of ventilation rates in window-aired rooms.
- Impact of Natural Ventilation on the Thermal and Energy Performance of Buildings in a Mediterranean ClimatePublication . Rodrigues, A. Moret; Santos, Miguel; Gomes, M. Glória; Duarte, RogérioNatural ventilation plays an important role on the thermal and energy performance of a building. The present study aims to analyze the natural ventilation conditions of a dwelling in a Mediterranean climate and their impacts on the thermal and energy performance using an advanced building energy simulation tool. Several multi-zone simulations were carried out. In the summer, the simulations were performed under free-floating conditions, whereas in the winter they were carried out under controlled temperature conditions. In the summer, ventilation scenarios with windows opened during certain periods of time and with or without permanent openings in the facades were analyzed. The existence of permanent openings proved to be an important factor of temperature control by lowering the average indoor zone temperatures during the day. Cross-ventilation also showed to be e ective. In the winter, we simulated the existence or absence of permanent openings for room ventilation and their surface area. The results showed that the stack e ect plays an important role in the ventilation and that in general it outperforms the wind e ect. Sizing permanent openings according to the standard guidelines proved to be adequate in providing the expected ventilation rates on an average basis.
- The effect of occupancy and environmental physical variables on classrooms’ natural ventilation: a path modeling approachPublication . Duarte, Rogério; Rodrigues, António Moret; Pimentel, Fernando; Gomes, Maria da GlóriaIn this paper, we use a path model to study natural ventilation in classrooms and research the link between air change rate, occupancy, and both outdoor and indoor physical variables. In general, the path model is derived from the building physics and occupant behavioral considerations via structural equation modeling (SEM), and allows for the use of continuous observable and unobservable factors. The latter are often employed in behavioral and social sciences to represent personal and group attributes. The path model is validated with data gathered during two consecutive academic years from four classrooms of a Portuguese school. The results confirm indoor and outdoor air temperature as major drivers of classroom ventilation, with standardized total path coefficients of approximately 0.55. Solar energy, precipitation, and occupancy are also significant drivers of classroom ventilation, with standardized total path coefficients of 0.24, −0.18, and 0.17, respectively. These results contribute to our understanding of the relative importance of occupancy as well as to identifying the most relevant environmental determinants of natural classroom ventilation. In spite of the statistical significance of the path model as a whole and its detailed causal relationships (direct, indirect, and feedback), only 58% of classroom ventilation variance is explained by the selected input variables. Because naturally ventilated classrooms depend significantly on occupants’ interactions with the built environment, i.e., opening/closing windows and blinds, extending path modeling to include additional personal and context-related drivers of occupants’ behavior would allow for further insights into the complex multi-domain topic of natural classroom ventilation.