Andrea Elvira Pattini

Passive solar systems for heating, daylighting and ventilation for rooms without an equator-facing facade

Spaces without northerly orientations have an impact on the ‘energy behaviour’ of a building. This paper outlines possible energy savings and better performance achieved by different zenithal solar passive strategies (skylights, roof monitors and clerestory roof windows) and element arrangements across the roof in zones of cold to temperate climates typical of the central and central-southern Argentina. Analyses were undertaken considering daylighting, thermal and ventilation performances of the different strategies. The results indicate that heating,ventilation and lighting loads in spaces without an equator-facing facade can be significantly reduced by implementing solar passive strategies. In the thermal aspect, the solar saving fraction reached for the different strategies were averaged 43.16% for clerestories, 41.4% for roof monitors and 38.86% for skylights for a glass area of 9% to the floor area. The results also indicate average illuminance levels above 500 lux for the different clerestory and monitor arrangements, uniformity ratios of 0.66–0.82 for the most distributed arrangements and day-lighting factors between 11.78 and 20.30% for clear sky conditions, depending on the strategy. In addition, minimum air changes rates of 4 were reached for the most extreme conditions.

Effects of perceived indoor temperature on daylight glare perception

This research investigates the effects of perceived indoor temperature on glare sensation. A laboratory experiment was carried out where volunteers (n = 19) performed an office-like computer task. Three scenarios with sunspots over the desk were evaluated: a cold scenario, a comfort scenario and a hot scenario. All had the same vertical illuminance at the eye and luminance ratios. Discomfort glare was measured with the predictive daylight glare probability (DGP) model; actual perception of glare was assessed with glare sensation vote (GSV) scale; while thermal comfort was evaluated with thermal sensation vote (TSV) scale. In order to know how much the perceived temperature contributes to the model, an ordinal regression was performed. The result showed a Nagelkerke pseudo-R2 = 0.52, p = 0.001, indicating that the perceived temperature affected glare predictions. This is an improvement in the understanding of daylight glare, which will allow researchers and practitioners to make informed decisions about sustainable design and occupant comfort. In conclusion, a more comprehensive glare model should include perceived temperature as a variable of the current glare model. Also, the results suggest that DGP should be used only when the person is in thermal comfort.

Glare and cognitive performance in screen work in the presence of sunlight

Research concerning the effects of glare on distraction is scarce. We designed a 2 × 2 repeated measures experiment (n = 32) in order to examine the influence of a large area glare source and glare sensitivity on reported discomfort glare and cognitive performance. Daylight glare probability was the within-subjects variable and glare sensitivity was the between-subjects variable. We found a statistically significant difference in glare sensation votes between scenarios, without statistically significant differences in glare ratings due to glare sensitivity. We found some statistically significant effects on our participants’ reaction times. Also, we calculated their effect sizes, which had practical relevance. Our results encourage further research in an issue that has been suggested since the early stages of glare research but has never been systematically and consistently addressed.

Análisis de las características morfológicas de las envolventes edilicias y del entorno urbano desde la perspectiva de la iluminación natural

Visual comfort and energy savings are results of the proper daylighting planning of spaces. As a first step to achieve these objectives we should be aware of the possibility of solar radiation access in the visible range of facades. This paper develops a descriptive morphological analysis of the urban, building, pass through component, and solar control system variables that determine access to visible radiation of a facade, considering regional variables. Its main objectives are: (a) to determine urban and building morphological caracteristics that affect access to visible solar radiation of front facades; and (b) to establish a diagnosis about the current state of these elements on front facades in the analyzed areas. This research work determines the importance of a detailed study of the front facade of buildings, given that 75% of the buildings analyzed have their central axis disposed perpendicularly to the front facade, 90% have no side retreats and 95% have a block building disposition. Likewise, it indicates that that there is no relationship between the use of openings and the solar control elements according to the regional clear sky climate.

Glare indicators: an analysis of ocular behaviour in an office equipped with venetian blinds

This article studies the ocular behaviour of office workers in the presence of glare. Additionally, the study seeks to obtain a new indicator for glare prediction that compensates the inaccuracies of glare predicted by the existing models of glare sensation vote (GSV), daylight glare probability (DGP) and daylight glare index. A laboratory experiment was carried out (n = 18) simulating an office space. The volunteers participated in four office tasks (reading from a screen and from a paper, writing and socializing). Two scenarios were evaluated: one with sunspots on the faces of the subjects and the other with sunspots on the working area. By means of a visible spectrum eye tracker these ocular parameters were registered: direction of gaze, the degree of opening of eye and pupil size. These ocular parameters were correlated with vertical illuminance at the eye. The results show that the degree of reduction of opening of the eye was the best predictor of visual discomfort with statistically significant differences between scenarios (p = –0.728, s = 0.001). The other important predictor was the pupil size. The degree of opening of eye and pupil size was correlated with glare indices. The degree of eye opening has a good correlation with GSV and DGP and it could be a future index of visual comfort under situations of the risk of glare.

Developing a modelling factor index for transition spaces: a case study approach

Transitional spaces (TS) are characterized by possession of high gradients of luminances between inside and out, which places a great demand on the users’ visual systems function. A satisfactory descriptive indicator of this kind of situation could be a ‘modelling factor’ (MF), defined from cylindrical illuminance and horizontal illuminance measures. It would provide information on the depth and dimensionality of objects present in the scene, also taking into account a regions overabundance of daylight. A public building was selected as a case study, and solar light behaviour, including its interaction with the space, was monitored. Measurements were taken during an entire year at the start of each season (2008) under clear skies, at the beginning and at the end of each working day. Another measurement was taken in winter (2009) under overcast skies at 13:00, so as to obtain a comparative parameter. It was found that unfavourable conditions were produced in all seasons for about 2 hours, except at 09:15 in winter. All the data collected in the control situation were within the optimum modelling range, with values ranging between 0.3 and 0.4. The MF allows the integration of most relevant factors intervening in TS and emerges as a good descriptor for TS.

Iluminación en unidades de cuidados intensivos neonatales: actualización y recomendaciones

Achieving adequate lighting in neonatal intensive care units is a major challenge: in addition to the usual considerations of visual performance, cost, energy and aesthetics, there appear different biological needs of patients, health care providers and family members. Communicational aspects of light, its role as a facilitator of the visual function of doctors and nurses, and its effects on the newborn infant physiology and development were addressed in order to review the effects of light (natural and artificial) within neonatal care with a focus on development. The role of light in regulating the newborn infant circadian cycle in particular and the therapeutic use of light in general were also reviewed. For each aspect, practical recommendations were specified for a proper well-lit environment in neonatal intensive care units.

Uso de dispositivo de control solar en aulas: impacto en la simulación dinámica de la iluminación natural

El uso de la iluminacion natural en los espacios educativos contribuye a mejorar desde diferentes perspectivas como la energia, salud y confort; sin embargo requiere de la cuidadosa planificacion en su diseno. El objetivo del presente trabajo es conocer el impacto del uso de sistemas de control solar en dos tipologias de aulas (orientacion N-S y E-O) representativas del parque edilicio regional, a traves de herramientas predictivas dinamicas del factor iluminacion natural de alta precision. La metodologia empleada fue: (a) relevamiento fisico y fotometrico in situ; (b) simulacion y analisis de metricas dinamicas e iluminacion artificial; y (c) evaluacion del impacto del uso de dispositivos de control solar (cortina textil). Los resultados evidenciaron una mayor autonomia de la iluminacion natural en la orientacion N-S con una alta probabilidad anual de deslumbramiento, aspecto que se revierte con el adecuado uso del dispositivo de control solar (DCS) propuesto. Asismismo, este DCS aumenta la iluminacion natural disponible (DAv= 12%) y disminuye su consumo de iluminacion artificial, en comparacion a la orientacionon (E-O). A partir de este nuevo enfoque, se busca profundizar en reducciones significativas de los consumos electricos (iluminacion) en los edificios de uso diurno, no solo incorporando la evaluacion predictiva nuevos sistemas de iluminacion artificial complementarios, sino tambien estrategias de control solar en pos del confort de los usuarios.

Effects of a Large Area Glare Source in Cognitive Efficiency and Effectiveness in Visual Display Terminal Work

Abstract Glare is a common visual stressor of office work and in todays offices the prevalence of information and communication technologies adds additional mental demands. The aim of this study was to explore the role of light as a cognitive stressor in visual display terminal (VDT) work. We used a large area light source in a 2 × 2 × 2 full factorial experimental design. We assessed cognitive efficiency using the RTLX method and cognitive effectiveness using the RST method in different lighting scenarios. The main effects analysis showed lower working memory capacity for high luminance and large source, with statistically significant lower cognitive performance in prosaccade conditions. No statistically significant relationship was found between cognitive efficiency and the experimental factors.AbstractGlare is a common visual stressor of office work and in todays offices the prevalence of information and communication technologies adds additional mental demands. The aim of this study was to explore the role of light as a cognitive stressor in visual display terminal (VDT) work. We used a large area light source in a 2 × 2 × 2 full factorial experimental design. We assessed cognitive efficiency using the RTLX method and cognitive effectiveness using the RST method in different lighting scenarios. The main effects analysis showed lower working memory capacity for high luminance and large source, with statistically significant lower cognitive performance in prosaccade conditions. No statistically significant relationship was found between cognitive efficiency and the experimental factors.

Iluminación natural en aulas: análisis predictivo dinámico del rendimiento lumínico-energético en clima soleados

En ciudades como Mendoza (Argentina), donde predomina el cielo claro con sol, la radiacion solar es lo suficientemente energetica en terminos de eficacia luminosa. Esto permite minimizar, y en algunos casos prescindir, de la energia electrica consumida por los espacios interiores durante las horas diurnas. El objetivo del presente trabajo es analizar y comparar la autonomia de la iluminacion natural y el consumo electrico en aulas representativas, tradicionales y bioclimaticas, construidas en la ciudad de Mendoza y el impacto de diferentes husos horarios. La metodologia empleada fue: relevamiento fisico y fotometrico de aulas reales, configuracion de archivos climaticos, y simulaciones y analisis de metricas dinamicas de iluminacion natural y consumos electricos para iluminacion. Los resultados evidenciaron: mayor autonomia de la iluminacion natural (15%) en aulas bioclimaticas; asimismo un aporte adicional del 3% a partir del uso horario UTC-4 (actualmente no vigente en Argentina, siendo el oficial el UTC-3); y un ahorro del 30% con la utilizacion de nuevas tecnologias de control de encendido-apagado en la iluminacion artificial. Los resultados obtenidos esperan contribuir a una mayor concientizacion sobre los beneficios de los edificios escolares energeticamente eficientes; como asi tambien la importancia de la iluminacion natural como factor influyente en la energia, salud y confort.