Ignacio Acosta

Analysis of circadian stimulus allowed by daylighting in hospital rooms

Light is the major synchronizer of circadian rhythms to the 24-hour solar day. Compared to the visual system, the circadian system requires more light to be activated and is more sensitive to short-wavelength light. Without access to daylight, or electric lighting providing a comparable amount, spectrum, distribution, duration, and timing, human health and well-being may be compromised. This may be particularly true for those confined indoors, such as patients in hospitals and residents in care facilities. Architectural and design features, including window size, surface reflectances, and furniture placement, impact circadian stimulus levels. This paper details results of simulations used to determine the percentage of days that patients would receive a minimum level of circadian stimulation as a function of different window-to-façade ratios, surface reflectances, and latitudes.

Climate-based daylighting analysis for the effects of location, orientation and obstruction

During the first stages of building design, issues such as local climate, surrounding buildings and orientation are determining factors. The impact of these boundary conditions on daylight illuminances in an open-plan office space is studied in terms of daylight factor, daylight autonomy and useful daylight illuminances. Climate conditions in the location determine the characteristics of the daylight source, such as the ratio between diffuse lighting and global lighting. However, surrounding buildings and elements which may block daylight in the space hold more weight than the orientation of glazed façades, but are not always taken into consideration in daylighting studies.

Climate-based daylight analysis of fixed shading devices in an open-plan office

Office buildings consume large amounts of energy and are responsible for large amounts of greenhouse gas emissions worldwide. Among building energy efficiency measures, solar shading plays a significant role in reducing building energy consumption for cooling. This study analysed the influence of solar protection on daylighting of an open-plan office. Climate-based daylight modelling was used to predict such metrics as daylight factor, daylight autonomy and useful daylight illuminances. The results obtained showed that overhangs, and horizontal and vertical louvres have similar behaviours and sidefins have no relevance to indoor daylight conditions. In all cases, it has been proven that excessive obstruction may yield an excessive reduction in a range of illuminances between 500 and 2000 lux, increasing lighting energy consumption.

Validation of a Dynamic Simulation of a Classroom HVAC System by Comparison with a Real Model

Schools require thermal comfort in their classrooms , but some uncertainty arises as how their HVAC systems will actually provide it, especially given their high internal loads and mechanical ventilation diffusion. Thus, it is necessary to resort to computational fluid dynamics (CFD) for developing predictive models; nevertheless, the reliability of the simulation tool has to be verified, so the main objective of this work is to define and perform the validation process of a thermal dynamic simulation tool by comparison with a real room. A validation protocol has been detailed for dynamic simulation tools, in medium-sized spaces with high internal loads, by comparing with the measured air temperature values of an existing standard classroom, according to ISO 7726:2002. The chosen standard classroom for this comparison belongs to “Eca de Queiros” secondary school of Lisbon (Portugal). To that effect, 80 thermocouple sensors were used for the characterization of its indoor thermal behaviour. A mean bias error (MBE) of 0.21 °C was obtained, with a maximum standard deviation of 0.47 °C, which is under the maximum limit of ±0.5 °C established by this standard. The application of this methodology for validating the Design Builder software proves the reliability of this tool in such type of venues.