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Abstract This paper describes a method for estimating ventilation rates in a window-aired room considering “in-use” conditions and uncertainty in occupancy (CO 2 release) and in measurements of indoor air CO 2 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 derived from knowledge of ventilation rates in window-aired rooms. Highlights • A state space model that considers uncertainty in occupancy and in measurements of indoor CO 2 concentration is derived. • A state observer based on this model and Kalman filtering successfully estimates ventilation rates in a window-aired room. • The link between the uncertainty in estimates of ventilation rate and the uncertainty in occupancy is discussed in detail. • Results for an existing classroom demonstrate the practical interest of knowing ventilation rates in window-aired rooms. [ABSTRACT FROM AUTHOR]

Classrooms in Southern Europe are traditionally ventilated with manual opening of windows. This is an energy-sparing and perfectly appropriate way of ventilating classrooms when weather conditions are warm, however, as outdoor air temperatures drop, teaching staff and students tend to leave windows closed and, as a consequence, ventilation rates fall leading to poor indoor air quality. To safeguard classrooms' indoor air quality and promote energy conservation, understanding the conditions for which manual window-airing is appropriate is of great relevance. Yet, given the stochastic nature of window-airing, it is difficult to get hold of this understanding. The main objective of this paper is to find out when manual window-airing of classrooms is appropriate. To achieve this objective, four free-running classrooms of a Portuguese public secondary school were monitored during a two-year period. Ventilation rates were determined and it is concluded that manual opening of windows provides appropriate ventilation for outdoor running mean temperatures larger than 19 °C. When outdoor running mean temperatures are lower than 16 °C, manual window-airing becomes inappropriate and, for outdoor running mean temperatures between 16 and 19 °C, appropriate manual window-airing depends on the indoor air temperature. For the studied classrooms, these results translate into appropriate ventilation for approximately a quarter of the academic year. Because of the significance of this finding, the paper concludes with a review of the ventilation strategy used in the studied classrooms. [ABSTRACT FROM AUTHOR]

Highly glazed buildings are typically responsible for significant solar heat gains/losses and, consequently, considerable cooling and heating energy needs throughout the year. Thermochromic glazing is an innovative passive technology, which autonomously and reversibly modifies its thermal and optical properties when direct sunlight heats it, potentially improving both energy efficiency and comfort. However, there is scarce evidence about the global performance of this glazing when installed in commercial buildings. Therefore, this study aims at assessing the annual visual, thermal and energy performance of a thermochromic glazing (12 + 12 + 6 mm) against a conventional clear glazing (6 + 12 + 4 mm) with and without a reflective solar control film installed in an existing office room, considering different European climates. To this aim, a building simulation model calibrated with experimental data obtained on a previous study was used. The results showed that in respect of the percentage of working hours with useful illuminance levels the thermochromic glazing (80%–88%) is better than the conventional clear glazing (64%–74%). However, the glazing with the reflective solar control film is more effective in reducing potential glare. Regarding the thermal performance assessment, under free-float conditions (no mechanical heating/cooling), the thermochromic glazing shows a better performance (20%–48% working hours within comfort conditions) when compared to conventional glazing (1%–42%). The results also show significant total energy savings (climate control and artificial lighting) in the case of the thermochromic glazing, particularly in the hot climate of Lisbon (50%). • Comfort and energy performance of thermochromic versus conventional static glazing. • Building simulation model of an office room calibrated with experimental data. • Up to 88% of working hours with useful illuminance with thermochromic glass. • Up to 48% of working hours within thermal comfort with thermochromic glass. • Up to 50% of energy savings with thermochromic glass when compared with clear glass. [ABSTRACT FROM AUTHOR]