Daylight Spectrum Index: A New Metric to Assess the Affinity of Light Sources with Daylighting

The current scenario of colorimetry shows a wide variety of different metrics which do not converge in the assessment of the color rendering of light sources. The limitations of the Color Rendering Index have promoted the emergence of new metrics, such as the Color Quality Scale. As in the case of the previous metric, these new concepts are based on the analysis of the deviation of different color samples in a color space, contrasting the results with those obtained with a light source reference, which can vary depending on the color temperature. Within this context, the Daylight Spectrum Index is proposed. This new concept aims to determine the affinity with daylighting of electric light sources, comparing the resulting spectral power distributions of the lamps studied and that observed under natural light. The affinity of an electric light source with daylighting allows for lower energy consumption due to the better performance of human vision. The new metric proposed is evaluated following the results obtained from 80 surveys, demonstrating the usefulness of this new concept in the quantification of color rendering of LED lamps and the affinity of electric light sources with daylighting.Government of Spain BIA2017-86997-

Dynamic Daylight Metrics for Electricity Savings in Offices: Window Size and Climate Smart Lighting Management

Daylight performance metrics provide a promising approach for the design and optimization of lighting strategies in buildings and their management. Smart controls for electric lighting can reduce power consumption and promote visual comfort using different control strategies, based on affordable technologies and low building impact. The aim of this research is to assess the energy efficiency of these smart controls by means of dynamic daylight performance metrics, to determine suitable solutions based on the geometry of the architecture and the weather conditions. The analysis considers different room dimensions, with variable window size and two mean surface reflectance values. DaySim 3.1 lighting software provides the simulations for the study, determining the necessary quantification of dynamic metrics to evaluate the usefulness of the proposed smart controls and their impact on energy efficiency. The validation of dynamic metrics is carried out by monitoring a mesh of illuminance-meters in test cells throughout one year. The results showed that, for most rooms more than 3.00 m deep, smart controls achieve worthwhile energy savings and a low payback period, regardless of weather conditions and for worst-case situations. It is also concluded that dimming systems provide a higher net present value and allow the use of smaller window size than other control solutions

Towards an Analysis of Daylighting Simulation Software

The aim of this article was to assess some of the main lighting software programs habitually used in architecture, subjecting them to a series of trials and analyzing the light distribution obtained in situations with different orientations, dates and geometry. The analysis examines Lightscape 3.2, Desktop Radiance 2.0, Lumen Micro 7.5, Ecotect 5.5 and Dialux 4.4

CO2 Concentration and Occupants’ Symptoms in Naturally Ventilated Schools in Mediterranean Climate

A large part of the school building stock in Andalusia lacks ventilation facilities, so that the air renewal of the classrooms is achieved through the building envelope (air infiltration) or the opening of windows. This research analyses the airtightness of the classrooms in Andalusia and the evolution of CO2 concentration during school hours through in situ monitoring. Pressurization and depressurization tests were performed in 42 classrooms and CO2 concentration was measured in two di erent periods, winter and midseason, to study the impact of the di erent levels of aperture of windows. About 917 students (11–17 years of age) were surveyed on symptoms and e ects on their health. The mean n50 values are about 7 h-1, whereas the average CO2 concentration values are about 1878 ppm, with 42% of the case studies displaying concentrations above 2000 ppm with windows closed

Analysis of Circadian Stimulus and Visual Comfort Provided by Window Design in Architecture

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. Daylighting is an ideal light source for circadian entrainment. Architectural and design features, such as window size and room reflectances impact the amount of circadian stimulus that the patient will receive. DaySim 3.2 simulations were used to determine the percentage of days that occupants would receive a minimum circadian stimulation of 0.50 for at least an hour during the morning. According to a phototransduction model of the human circadian system, a circadian stimulation of 0.50 is equivalent to suppressing the hormone melatonin by about 50%. This circadian stimulus criterion is examined for different window to wall ratios, for two average room reflectances, and for four latitudes. The present paper provides an example of a tool that could be used to assist designers in fenestration and interior design

Minimum daylight autonomy: A new concept to link daylight dynamic metrics with daylight factors

Daylight metrics act as a useful tool to quantify the potential of natural light in an architectural space as well as the energy savings promoted by a suitable design of windows, atriums, and skylights. Accordingly, a new indoor lighting metric is proposed, minimum daylight autonomy, defined as the percentage of occupied time when an illuminance threshold can be met by daylight alone under continuous overcast sky conditions. This novel concept can determine an approximation of the maximum use of electric lighting and the quantification of minimum energy savings without the need for advanced calculation tools. Although daylight factor is the most widespread concept, it cannot forecast energy savings as accurately as dynamic metrics. In addition, daylight autonomy is the most usual dynamic definition, because it estimates the energy consumption of on–off electric lighting systems depending on weather conditions. However, there is no link between static and dynamic metrics, because both concepts are based on different variables. This research proposes the calculation procedure for minimum daylight autonomy, as well as the equations that serve to predict dynamic metrics based on static metrics, after confirming the accuracy of the simulation program that calculates the metrics using a test cell under real conditions

Indoor comfort and symptomatology in non-university educational buildings: occupants’ perception

The indoor environment in non-university classrooms is one of the most analyzed problems in the thermal comfort and indoor air quality (IAQ) areas. Traditional schools in southern Europe are usually equipped with heating-only systems and naturally ventilated, but climate change processes areboth progressively increasing average temperatures and lengthening the warm periods. In addition,air renewal is relayed in these buildings to uncontrolled infiltration and windows’ operation, buturban environmental pollution is exacerbating allergies and respiratory conditions among the youthpopulation. In this way, this exposure has a significant effect on both the academic performanceand the general health of the users. Thus, the analysis of the occupants’ noticed symptoms and their perception of the indoor environment is identified as a potential complementary tool to a more comprehensive indoor comfort assessment. The research presents an analysis based on environmentalsensation votes, perception, and indoor-related symptoms described by students during lessons contrasted with physical and measured parameters and operational scenarios. This methodology is applied to 47 case studies in naturally ventilated classrooms in southern Europe. The main conclusionsare related to the direct influence of windows’ operation on symptoms like tiredness, as well asthe low impact of CO2 concentration variance on symptomatology because they usually exceeded recommended levels. In addition, this work found a relationship between symptoms under study with temperature values and the environmental perception votes, and the special impact of the lack of suitable ventilation and air purifier systems together with the inadequacy of current thermal system

Dynamic analysis of office lighting smart controls management based on user requirements

Daylight dynamic metrics provide an alternative approach for the assessment of the energy savings promoted by lighting control systems. This research aims to quantify the energy savings allowed by lighting smart controls using continuous and overcast daylight autonomy, novel metrics tested monitoring a mesh of illuminance-meters in test cells over a one-year period. Three types of smart controls are proposed, based on switches and dimmers, some of which were managed by illuminance-meters and irradiance detectors. Energy savings are assessed according to weather data, room dimensions, inner reflectances, window size and user requirements—illuminance needs and working hours. The results show a reduction in the average energy consumption of electric lighting of up to 23%, suggesting the suitability of the smart controls proposed. Smart controls without illuminance-meter feedback are only recommended for shallow rooms with low requirements, while dark deep rooms demand a complex dimming system managed by external illuminance-meters

Smart controls for lighting design: towards a study of the boundary conditions

This research aims to determine the effect of the lighting smart controls in the energy consumption in buildings, according to the geometry of the room, the window size, the reflectance of the inner surfaces and the location of study. For this purpose, two lighting smart controls are proposed: one based in an On/Off lighting control with separated lines and other with a dimming control. The analysis of both control systems is carried out by using daylight dynamic metrics, such as the daylight autonomy and the continuous daylight autonomy. The results quantify the effect of the architectural variables of the room in the performance of the lighting smart controls

Covid airborne risk: online tool to develop healthy buildings

Airborne transmission has been widely proven to be the main means of contagion of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) , as multiple studies have established (Greenhalgh et al., 2021; Miller et al., 2021; Lidia Morawska & Cao, 2020; Tang et al., 2021; World Health Organization, 2021), Furthermore, the main documented COVID-19 outbreaks have occurred indoors (Qian et al., 2021; Randall et al., 2021; Wang et al., 2022), with medium and long-range transmission —beyond 1.5 m— as a especially relevant transmission way in poorly bad ventilated spaces (Li, 2021; Z. Peng et al., 2022). Thus, it is necessary to promote healthy indoor spaces through self-protection practices and an adequate indoor air quality (IAQ). In this way, the removal of the virus-containing aerosols from indoor air —either by ventilation, air filtration or UV radiation— must be an essential part of the prevention strategy. One of the main ways to assess the degradation of the IAQ in occupied spaces —with no other significant sources or sinks of indoor carbon dioxide (CO2) — is monitoring the indoor CO2 level. This parameter can be a good proxy —affordable and easy to handle— to evaluate and control the aforementioned ventilation rates, especially in spaces with high occupancy density (American National Standards Institute and American Society of Heating Refrigerating and Air-Conditioning Engineers, 2019; Pavilonis, Ierardi, Levine, Mirer, & Kelvin, 2021; Z. Peng et al., 2022; Persily & de Jonge, 2017; Zhu et al., 2020). Given that virus-containing aerosols are emitted during the respiratory process as CO2 does, the measurement of the excess CO2 level exhaled (∆CO2) can also be used to estimate the airborne transmission risk of respiratory diseases such SARS-CoV-2, tuberculosis, or measles. Thus, the estimation of the COVID-19 infection risk indoors ―strictly via aerosols― can be performed with the online tool COVID Risk airborne (https://www.covidairbornerisk.com/), a non-profit software developed by Campano et al. (Campano-Laborda et al., 2021) and based on the adaptation of the Wells-Riley model (Rudnick & Milton, 2003) performed by Peng and Jiménez (Jimenez Palacios & Peng, 2021; Zhe Peng & Jimenez, 2021). The methodology on which this tool is based has been validated by comparison with existing COVID-19 outbreaks (Z. Peng et al., 2022). This tool (Figure 1), which has been designed to be used both by scientists and technicians (detailed calculation) and by nonprofessional users (simplified calculation), uses the average excess CO2 level exhaled (∆CO2) during a given event as a proxy to calculate how many 'quanta' inhaled each occupant (a 'quanta' can be considered as the minimum infectious dose of the aerosol pathogen whose inhalation leads to infection in 63% of vulnerable people). Inhalation of quanta depends on: SARS-CoV-2 variant under analysis. Room dimensions and environmental conditions (rate of decay of infection intensity and surface deposition rate). Removal/inactivation of aerosols from the environment (filtering, UV exposure, face masks). Number of people present, number of infectious occupants, activity involved (metabolic and vocalization) and immunity to the infection (by vaccines or previous infections). Event duration. Ventilation rate / Mean ∆CO2 value during the event. With this data input, this tool can estimate both the number of secondary cases in the given event, and the Risk of Infection (H) ―in terms of the size of the outbreak―, but it can also calculate two additional risk indicators, which are not referred to the number of vulnerable occupants (those who are liable to contract the disease), so they can be used regardless of the number of people vaccinated or the effectiveness of the different vaccines: Attack rate (AR): The proportion of occupants in the event who could have inhaled a 'quanta'. Relative risk of infection (Hr): Number of 'quanta' emitted by a single infected person which are inhaled by a single person for a given exposure time and premises of the volume specified. There are three categories of risk (low, medium, and high) for Hr, according to previous studies of different indoor scenarios and existing documented outbreaks (Z. Peng et al., 2022; Zhe Peng & Jimenez, 2021). Among the various considerations made by this tool, it should be noted that: The model EXCLUDES droplet and contact/fomite transmission and assumes that 2 m (6 ft) social distancing is honoured. Otherwise, the infection rates calculated would be higher. As the model also assumes the atmosphere in the premises/room at issue to be uniformly distributed, it does not accommodate the thermal stratification or floatability characteristic of very high clearance indoor spaces. The increased transmissibility of the SARS-CoV-2 variants is obtained from the reports of the European and North American Centres for Disease Control and Prevention (Campbell et al., 2021; Centers for Disease Control and Prevention, 2022). The estimation of the airborne viral emission is performed through the expiratory activity, which depends on the metabolic and vocalization activities (Buonanno, Stabile, & Morawska, 2020; L. Morawska et al., 2009). The evaluation of the average ventilation rate and the recommended short-term exposure values for inhalation, in m³/h per occupant, are calculated through the metabolic rate, which depends on activity, age and gender (Z. Peng et al., 2022; Wang, Wang, Wei, Wang, & Duan, 2011), as well as the CO2 emission (Persily & de Jonge, 2017). The decay rate of the virus infectivity in aerosols depends on the Air Temperature (Ta), Relative Humidity of the air (HR), the UV index and the deposition of virus-containing aerosols to surfaces (Schuit et al., 2020; Smither, Eastaugh, Findlay, & Lever, 2020; van Doremalen et al., 2020). The theoretical aerosol retention efficiency of masks, respirators and face shields depends on the type of the mask and its fitting (Davies et al., 2013; Melikov, 2015; Milton, Fabian, Cowling, Grantham, & McDevitt, 2013). In conclusion, this online tool proposes a validated and precise method for simulating SARS-CoV-2 disease propagation, strictly via aerosols. One possible purpose would be to determine the risk of infection under circumstances defining a given planned event and the possibility of lowering such risk. Whilst it is not an epidemiological model, it can be used as a component of such approaches to estimate variations in aerosol propagation across a range of inputs. Thus, it can be very useful to scientists, technicians, building managers, designers, and citizens to reduce the risk of airborne transmission of SARS-CoV-2 in indoor events