Thermal and Lighting Consumption Savings in Classrooms Retrofitted with Shading Devices in a Hot Climate

Abstract

Most educational buildings in southern Spain do not meet current energy requirements as weak thermal envelopes and the lack of cooling systems lead to severe discomfort in classrooms, especially when temperatures are above 30 • C. Given that global warming is expected to worsen this situation in coming decades, one of the first steps to be taken is to protect window openings from high levels of solar radiation by adding shading devices to reduce indoor temperatures and improve visual comfort. The aim of this research is to evaluate the reduction in thermal and lighting consumption in a classroom where a solar protection system in the form of an egg-crate shading device was installed. Two classrooms-one with an egg-crate device and another with no shading system-were monitored and compared for a whole year. The use of an egg-crate device in these classrooms reduced indoor operative temperatures during warmer periods while also improving indoor natural illuminance levels. Moreover, annual electric air conditioning consumption decreased by approximately 20%, with a 50% reduction in electric lighting consumption. These savings in electricity were largely conditioned by the use patterns observed in these ambient systems.Energies 2018, 11, 2790 2 of 17 were therefore considered potential components for the reduction of energy consumption, but this is also conditioned by user patterns, as concluded in the laboratory experiments by Zeiler et al. [7].While solar radiation through glazed surfaces severely affects indoor temperatures and visual comfort, heat gains through window openings improve natural illuminance levels and increase indoor temperatures in winter, causing visual discomfort and overheating in summer. Although solar energy facilitates the passive heating of buildings, excessive solar gains can lead to overheating and glare, so that solar control systems must therefore cover aspects such as thermal and visual comfort and energy saving. Although it should be possible to look out and maintain visual contact with the exterior while respecting the architectural aesthetics of the building, the main function of shading devices is to reduce solar gains in the summer season.Various authors have attempted to establish a classification [8] and comparative evaluation of different solar-control systems [9] using integrated solutions for energy, acoustic, and lighting performances [10]. Much of this analysis focuses on the impact on energy requirements [11] and energy demand [12] in office buildings. Dynamic control strategies are needed to promote optimum performance of these shading devices given the opposing requirements in winter and summer.Eltaweel and Su [13] proposed modifying the position and angle of Venetian blinds, using Grasshopper's plugins to optimize daylight in office buildings, whereas other authors preferred simplified solutions which are easier to apply in building refurbishment. Freewan [14] compared the effect of different external vertical and diagonal fins and egg-crate devices behind a brise-soleil...

Assessment of Indoor Environmental Quality for Retrofitting Classrooms with An Egg-Crate Shading Device in A Hot Climate

“…The results presented in this paper complement the conclusions of previous research as part of the same case study conducted by the authors [41], where the influence of a low-cost egg-crate shading device made of methacrylate on the annual electricity consumption (kWh) of the classrooms was analyzed for three seasonal periods (winter, summer, and mid-season). Among the conclusions of the paper referenced, it should be highlighted that the use of these devices allows for significant savings in annual electricity consumption of the air-conditioning system (20%) and artificial lighting (50%), when compared to a classroom with no egg-crate shading devices.…”

“…A descriptive statistical analysis was conducted using the integrated development environment (IDE) of Matlab [42]. Unlike the earlier research [41], this paper focuses on the analysis of the influence of the egg-crate shading device on different ambient variables related to indoor comfort: incident solar radiation (W/m 2 ), indoor operative temperature ( • C) and indoor natural illuminance (lux). To assess the real impact of the device, different occupied and unoccupied periods were selected.…”

“…The main aim of this paper is to assess the impact of an egg-crate shading device, that is, one made of combined vertical and horizontal shading elements, on the IEQ for the retrofitting of an educational building, considering real user patterns. This type of device, among several other existing types [39,40], is particularly effective in regions with a hot climate as it produces highly efficient shading while allowing people to see outside [41].…”

Indoor Air Quality Assessment: Comparison of Ventilation Scenarios for Retrofitting Classrooms in a Hot Climate

“…Once the geometrical, physical, and constructive characterization of the classroom was obtained [46], an energy simulation model was constructed to analyze the influence of the ventilation scenarios above on the indoor thermal performance and electricity consumption of the ventilation systems. Neither air heat treatment nor heat recovery systems were considered for the ventilation design.…”

A review of lighting research in educational spaces

“…During this decade, daylighting and electric lighting were in focus, with daylight-related research being included in fourteen out of twenty-four studies, meaning that more than half of the papers are investigating daylight related aspects in school classrooms (3,(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). The number of studies that focussed on electric lighting in school classrooms is twelve (1,36,42,(45)(46)(47)(48)(49)(50)(51)(52)(53).…”