Indoor Light Levels Research Articles

What Limits the Voltage of GaAs Photovoltaic Devices under Low Indoor Light?

The external radiative efficiency of a photovoltaic device is a useful metric to compare different photovoltaic technologies and material systems. However, under low‐intensity indoor lighting, a particular open‐circuit voltage dependence arises that cannot be described using the assumption of a constant external radiative efficiency, as often assumed at higher illumination intensities. As a result, the external radiative efficiency at 1 sun conditions no longer becomes a useful comparison metric for devices at indoor lighting levels. By use of absolute electroluminescence measurements of gallium arsenide photovoltaic (PV) cells, the current density dependence of the external radiative efficiency is explored and it is shown that the functional form of this dependence dictates the open‐circuit voltage losses in the low‐intensity limit. This dependence is quantified with a mathematical treatment that takes advantage of a widely accepted recombination current model in III–V photovoltaic devices, and this model is used to study the dependence of PV device open‐circuit voltage at low intensity with varying non‐radiative recombination rates.

Development of smart spectacles to monitor and modify myopia‐related health behaviour in children

To develop a wearable, spectacle-mounted, sensor-based device to monitor and modify myopia risk factors in children, namely near-working distance, light levels and spectral composition. A wearable, spectacle-mounted device has been developed, which consists of inbuilt sensors, namely: (i) light sensor to detect ambient light intensity; (ii) proximity sensor to measure near-work distance; (iii) microspectrograph to measure spectral power for six visible channels, namely red, green, blue, yellow, orange and violet and (iv) a global positioning system tracker to track the location and the device. The sensors were programmed by Arduino Nano, and the circuit was fixed onto a printed circuit board fitted onto a spectacle frame for pilot testing. Laboratory testing of the prototype was performed using a mannequin. An alert will be set when exceeding the predetermined threshold to help control myopia risk factors. The indoor and outdoor light levels measured using the prototype were less than and greater than 1000 lux, respectively. The actual target distance and the corresponding distance measured by the prototype were highly correlated (R2 =0.99). The mean distance measured by the prototype was within 1.5cm of the actual target distance for distances between 30 and 95 cm. The spectral energy of the indoor location was highest for the orange channel at about 100-160 counts/μW/cm2 , whereas it was highest for the blue channel in outdoor daylight (10,000-19,000 counts/μW/cm2 ). A working prototype that can simultaneously measure the viewing distance, light intensity and spectral composition has been developed.

Potted plants can remove the pollutant nitrogen dioxide indoors

Nitrogen dioxide (NO2) is a significant pollutant in both outdoor and indoor environments with exposure linked to serious respiratory illnesses, decreased lung function and airway inflammation. Here, we investigate whether potted plants can contribute as a simple and cost-effective indoor air pollution mitigation technique. Our study investigates the ability of the combination of the three plant species Spathiphyllum wallisii ‘Verdi’, Dracaena fragrans ‘Golden Coast’ and Zamioculcas zamiifolia with two different growing media to remove in situ concentrations (100 ppb) of NO2 in real-time at two typical indoor light levels (0 and 500 lx) and in ‘wet’ and ‘dry’ growing media conditions. All studied ‘growing medium–plant systems’ were able to reduce NO2 concentrations representative of a polluted urban environment, but to varying degrees. The greatest NO2 removal measured inside a 150 L chamber over 1-h period in ‘wet’ growing media at ~ 500 lx was achieved by D. fragrans. When accounting for dilution, this would correspond to a removal of up to 3 ppb NO2 per m2 of leaf area over the 1-h test period and 0.62 ppb per potted plant over the same period when modelled for a small office (15 m3) in a highly polluted environment. Depending on building ventilation rates and NO2 concentration gradients at the indoor-outdoor interface that will vary massively between polluted urban and rural locations, potted plants offer clear potential to improve indoor air quality—in particular in confined indoor spaces that are poorly ventilated and/or located in highly polluted areas.

Mobility Performance in Retinitis Pigmentosa Under Different Lighting Simulation Conditions

This study examined the mobility performance in retinitis pigmentosa (RP) under different simulation lighting conditions. A total of twenty-one subjects with RP and twenty-one age-matched controls were enrolled. Preferred Walking Speed (PWS) were determined using a simple mobility course at 61 cd/m2 while Percentage of Preferred Walking Speed (PPWS) and error score were determined at five different illumination level which were 62, 47, 20, 6 and 1 cd/m2 using a complex mobility course. RP and normal people had similar mobility performances in simple mobility situations at a constant high light level. In lower light levels as well as in complex mobility situations, RP subjects demonstrated markedly reduced mobility performance. The relationship between PPWS and luminance was linear, with the PPWS decreasing significantly when the mobility course luminance dropped below the illumination of 20 cd/m2 . The Error score was also noted to be linearly related to log luminance. A luminance level of 20 cd/m2 may provide a useful decision point in setting indoor light levels for clinical mobility courses.

Mobility Performance in Retinitis Pigmentosa Under Different Lighting Simulation Conditions

This study examined the mobility performance in retinitis pigmentosa (RP) under different simulation lighting conditions. A total of twenty-one subjects with RP and twenty-one age-matched controls were enrolled. Preferred Walking Speed (PWS) were determined using a simple mobility course at 61 cd/m2 while Percentage of Preferred Walking Speed (PPWS) and error score were determined at five different illumination level which were 62, 47, 20, 6 and 1 cd/m2 using a complex mobility course. RP and normal people had similar mobility performances in simple mobility situations at a constant high light level. In lower light levels as well as in complex mobility situations, RP subjects demonstrated markedly reduced mobility performance. The relationship between PPWS and luminance was linear, with the PPWS decreasing significantly when the mobility course luminance dropped below the illumination of 20 cd/m2 . The Error score was also noted to be linearly related to log luminance. A luminance level of 20 cd/m2 may provide a useful decision point in setting indoor light levels for clinical mobility courses.

Mobility Performance in Retinitis Pigmentosa Under Different Lighting Simulation Conditions

This study examined the mobility performance in retinitis pigmentosa (RP) under different simulation lighting conditions. A total of twenty-one subjects with RP and twenty-one age-matched controls were enrolled. Preferred Walking Speed (PWS) were determined using a simple mobility course at 61 cd/m2 while Percentage of Preferred Walking Speed (PPWS) and error score were determined at five different illumination level which were 62, 47, 20, 6 and 1 cd/m2 using a complex mobility course. RP and normal people had similar mobility performances in simple mobility situations at a constant high light level. In lower light levels as well as in complex mobility situations, RP subjects demonstrated markedly reduced mobility performance. The relationship between PPWS and luminance was linear, with the PPWS decreasing significantly when the mobility course luminance dropped below the illumination of 20 cd/m2 . The Error score was also noted to be linearly related to log luminance. A luminance level of 20 cd/m2 may provide a useful decision point in setting indoor light levels for clinical mobility courses.

Mobility Performance In Retinitis Pigmentosa Under Different Lighting Simulation Conditions

This study examined the mobility performance in retinitis pigmentosa (RP) under different simulation lighting conditions. A total of twenty-one subjects with RP and twenty-one age-matched controls were enrolled. Preferred Walking Speed (PWS) were determined using a simple mobility course at 61 cd/m2 while Percentage of Preferred Walking Speed (PPWS) and error score were determined at five different illumination level which were 62, 47, 20, 6 and 1 cd/m2 using a complex mobility course. RP and normal people had similar mobility performances in simple mobility situations at a constant high light level. In lower light levels as well as in complex mobility situations, RP subjects demonstrated markedly reduced mobility performance. The relationship between PPWS and luminance was linear, with the PPWS decreasing significantly when the mobility course luminance dropped below the illumination of 20 cd/m2 . The Error score was also noted to be linearly related to log luminance. A luminance level of 20 cd/m2 may provide a useful decision point in setting indoor light levels for clinical mobility courses.

Ambient bright light treatment improved proxy-rated sleep but not sleep measured by actigraphy in nursing home patients with dementia: a placebo-controlled randomised trial

BackgroundUp to 70% of nursing home patients with dementia suffer from sleep problems. Light is the main zeitgeber to the circadian system and thus has a fundamental impact on sleep-wake behaviour. Low indoor light levels in nursing homes have been reported, and in combination with age-related reductions in light sensitivity, insufficient light exposure is likely to contribute to sleep problems in this population. Increasing daytime light exposure using bright light treatment (BLT) may represent a feasible non-pharmacological treatment for sleep problems in nursing home patients with dementia.MethodsThe present study reports on sleep outcomes, which are the primary outcomes of the DEM.LIGHT trial (Therapy Light Rooms for Nursing Home Patients with Dementia– Designing Diurnal Conditions for Improved Sleep, Mood and Behavioural Problems), a 24-week cluster-randomised placebo-controlled trial including 8 nursing home units and 69 resident patients. The intervention comprised ambient light of 1000 lx and 6000 K from 10:00 to 15:00, with gradually increasing and decreasing light levels prior to and following this interval, using ceiling mounted light-fixtures and light emitting diode technology. The placebo condition had continuous standard light levels (150–300 lx, ~ 3000 K). Sleep was assessed at baseline and follow-up at week 8, 16, and 24, using the proxy-rated Sleep Disorder Inventory (SDI) and actigraphy (Actiwatch II, Philips Respironics). Mixed linear models were used to evaluate intervention effects, adjusting for relevant covariates such as age, gender, number of drugs, severity of dementia, eye disease, and estimated light exposure.ResultsSleep as measured by the SDI was significantly improved in the intervention group compared to the control group from baseline to week 16 (B = − 0.06, 95% CI -0.11 - -0.01, p < .05) and from baseline to week 24 (B = − 0.05, 95% CI -0.10 - -0.01, p < .05). There was no effect according to the SDI at week 8 and no significant effects in terms of actigraphically measured sleep.ConclusionsProxy-rated sleep improved among nursing home patients with dementia following 16 and 24 weeks of BLT. These improvements were not corroborated by actigraphy recordings.Trial registrationClinicalTrials.gov Identifier: NCT03357328. Registered 29 November 2017 – Retrospectively registered.

Relationship between indoor environmental quality and sick building syndrome: a case study of selected student’s hostels in Southwestern Nigeria

An improved indoor environmental quality (IEQ) is a major determinant of human comfort in an occupied space. The current cross-sectional study investigates the link between indoor environmental quality (IEQ) and sick building syndrome symptoms (SBS) emergence with a case study of selected students’ hostels in a Nigerian private university. A quantitative research design method was adopted where 376 (n = 376) copies of the questionnaire were purposely administered to the student’s occupants. A mini environmental quality meter was also objectively used to measure the indoor air temperature, relative humidity, air velocity, and lighting levels in the selected hostel rooms in February and March 2019. The data obtained were subjected to descriptive and analysis of variance (ANOVA) inferential statistics using the Statistical Package for Social Sciences (SPSS) 25.0 version. The research findings revealed that students show SBS symptoms like tiredness, sensitivity to odor, sneezing, and blocked nose during their hostels’ occupancy. Meanwhile, the objective measurement results showed an average indoor temperature of 29.93 °C, 31.64 °C, and 30.71 °C. Simultaneously, average relative humidity values of 79.00%, 72.06%, and 81.01% were obtained in the monitored rooms for the morning, afternoon, and evening. The ANOVA result established a positive relationship between poor IEQ condition and the SBS symptoms of odor, stuffy nose, and nausea. Therefore, it is recommended that the hostel facilities’ SBS be mitigated through acceptable IEQ parameters of air temperature and relative humidity, increasing students’ wellbeing, academic performance, and reputation.

Photon mapping of geometrically complex glass structures: Methods and experimental evaluation

Advances in digital fabrication and additive manufacturing have enabled the creation of geometrically complex glass structures and building components, opening up new design opportunities across scales. Quantifying and evaluating their optical performance, however, remains a technical challenge. In order to accurately predict light behavior, common approaches of daylight modeling utilizing light-backward raytracers are insufficient. This paper evaluates the use of the photon mapping approach within the Radiance render engine to simulate artificial and natural lighting conditions. 3D printed optically transparent glass components are used to benchmark the simulations. We present a workflow to gather geometric data of the glass objects and a series of validation experiments. Pairs of physical studies and digital simulations are compared to assess optical performance in the context of both indoor and outdoor lighting conditions. These experiments demonstrate that the photon mapping approach can reliably measure and predict caustic light patterns and indoor light levels with some limitations, specifically of glare and scattered light from the glass objects themselves.

Light-based monitoring devices to assess range use by laying hens

Access to an outdoor range has many potential benefits for laying hens but range use can be poor due to factors only partly understood. Techniques to monitor individual range use within commercial flocks are crucial to increase our understanding of these factors. Direct observation of individual range use is difficult and time-consuming, and automatic monitoring currently relies on equipment that is difficult to use in an on-farm setting without itself influencing range use. We evaluated the performance of a novel small, light and readily portable light-based monitoring system by validating its output against direct observations. Six commercial houses (2000 hens/house) and their adjacent ranges were used, three of which were equipped with more structures on the range than the others (to determine whether cover would influence monitoring accuracy). In each house, 14 hens were equipped with light monitoring devices for 5 discrete monitoring cycles of 7 to 8 consecutive days (at 20, 26, 32, 36 and 41 weeks of age). Light levels were determined each minute: if the reading on the hen-mounted device exceeded indoor light levels, the hen was classified as outside. Focal hens were observed directly for 5 min/hen per week. Accuracy (% of samples where monitoring and direct observations were in agreement) was high both for ranges with more and with fewer structures, although slightly better for the latter (92% v. 96% ± 1 SEM, F1,19 = 5.2, P = 0.034). Furthermore, accuracy increased over time (89%, 94%, 95%, 98% ± 1 SEM for observations at 26, 32, 36 and 41 weeks, respectively, F3,19 = 3.2, P = 0.047), probably due to progressively reduced indoor light levels resulting from partial closing of ventilation openings to sustain indoor temperature. Light-based monitoring was sufficiently accurate to indicate a tendency for a greater percentage of monitored time spent outside when more range structures were provided (more: 67%, fewer: 56%, SEM: 4, χ12 = 2.9, P = 0.089). Furthermore, clear and relatively consistent individual differences were detected. Individuals that were caught outside at the start of the experiment ranged more throughout its duration (caught outside: 72%, caught inside 51%, SEM: 4, χ12 = 10.0, P = 0.002), and individual range use was correlated between monitoring cycles (for adjacent monitoring cycles: rs2 = 0.5−0.7, P < 0.0001). This emphasizes the importance of studying range use on an individual level. In conclusion, our light-based monitoring system can assess individual range use accurately (although accuracy was affected by house characteristics to some extent) and was used to show that both cover availability and individual characteristics affected range use.

The Effects of Different Outdoor Environments, Sunglasses and Hats on Light Levels: Implications for Myopia Prevention.

PurposeLack of outdoor time is a known risk factor for myopia. Knowledge of the light levels reaching the eye and exposure settings, including sun-protective measures, is essential for outdoor programs and myopia. We evaluated the impact of sun-protective strategies (hat and sunglasses) on maintaining high illuminance levels to prevent myopia.MethodsA child-sized mannequin head was developed to measure light illuminance levels with and without sun-protective equipment, across a wide range of environments in Singapore, outdoors (open park, under a tree, street) and indoors (under a fluorescent illumination with window, under white LED-based lighting without window). A comparison was made between indoor and outdoor light levels that are experienced while children are involved in day-to-day activities.ResultsOutdoor light levels were much higher (11,080–18,176 lux) than indoors (112–156 lux). The higher lux levels protective of myopia (>1000 lux) were measured at the tree shade (5556–7876 lux) and with hat (4112–8156 lux). Sunglasses showed lux levels between 1792 and 6800 lux. Although with sunglasses readings were lower than tree shade and hat, light levels were still 11 to 43 times higher than indoors.ConclusionsRecommendations on spending time outdoors for myopia prevention with adequate sun protection should be provided while partaking in outdoor activities, including protection under shaded areas, wearing a hat or sunglasses, sunscreen, and adequate hydration.Translational RelevanceLight levels outdoors were higher than indoors and above the threshold illuminance for myopia prevention even with adequate sun-protective measures.

Adaptive biomimetic facades: Enhancing energy efficiency of highly glazed buildings

In this paper, we investigate the design of an adaptive biomimetic facade as a practical solution for enhancing energy efficiency of highly glazed buildings in the hot and humid regions. We present an adaptive facade that reduces solar heat gain and hence the energy consumption of the building, with minimal reduction in visual comfort (i.e., indoor lighting levels and visibility to the outer environment) of the users. The basic module of the facade consists of four shading devices that can be folded along both horizontal and vertical axes. The design enables shading under both high and low sun angles, without blocking visibility to the outdoor environment. To develop the facade, we explore and mimic the physical, physiological and adaptation properties of an Oxalis oregana—a leaf that has the natural ability to track sun path and change its angle/position accordingly. As a case study for the proposed facade, we take an existing 20-story office building in the hot and humid climate of Lahore, Pakistan. Our numerical results indicate that after retrofitting of the designed facade, the building's existing energy load decreases by 32%. Moreover, 50% of the interior space (as opposed to 55% before the retrofitting) still has lighting level within the recommended range of 500–750 lux. The investigation demonstrates that the proposed biomimetic facade can significantly reduce the energy consumption, with minimal reduction in visual comfort, of highly glazed buildings.

Shedding Some Light in the Dark-A Comparison of Personal Measurements with Satellite-Based Estimates of Exposure to Light at Night among Children in the Netherlands.

Background:Exposure to light at night (LAN) can perturb the biological clock and affect sleep and health. Previous epidemiological studies have evaluated LAN levels measured by satellites, but the validity of this measure as a proxy for personal LAN exposure is unclear. In addition, outdoor satellite-measured LAN levels are higher in urban environments, which means that this measure could potentially represent a proxy for other, likely urban, environmental exposures.Objectives:We evaluated correlations of satellite-assessed LAN with measured bedroom light levels and explored correlations with other environmental exposures, in particular, air pollution, green space, and area-level socioeconomic position (SEP).Methods:We compared satellite measurements with evening and nighttime bedroom measurements of illuminance (in units of lux) for 256 children, and we evaluated correlations between satellite-based measures and other urban exposures such as air pollution, area-level SEP, and surrounding green space for 3,021 children.Results:Satellite-measured LAN levels (nanowatts per centimeter squared per steradian) were not correlated with measured evening or nighttime lux levels [Spearman correlation coefficients () to 0.04]. There was a weak correlation with measurements during the darkest time period if parents and their children reported that outdoor light sometimes or usually influenced indoor light levels (, ). In contrast, satellite-measured LAN levels were correlated with air pollution ( with , with ), and surrounding green space ( for green space within of the home). A weak correlation with area-level SEP was also observed ().Conclusions:Outdoor satellite-assessed outdoor LAN exposure levels were correlated with urban environmental exposures, but they were not a good proxy for indoor evening or nighttime personal exposure as measured in our study population of 12-y-old children. Studies planning to evaluate potential risks from LAN should consider such modifying factors as curtains and indoor lighting and the use of electronic devices and should include performing indoor or personal measurements to validate any exposure proxies. The moderate-to-strong correlation of outdoor LAN with other environmental exposures should be accounted for in epidemiological investigations. https://doi.org/10.1289/EHP3431

Continuous Objective Assessment of Near Work

Evidence regarding the role of near work in myopia is conflicting. We developed the RangeLife, a device for continuous, objective measurement of working distance. Four devices were built, calibrated, and validated. Then, adult subjects wore the device on weekdays and weekend days, while simultaneously wearing an actigraph device for objective measurements of light exposure and activity. Subjects maintained an activity log and answered a visual activity questionnaire. RangeLife data were downloaded and binned into 0.10 m intervals. Objective diopter hours (dh), a weighted measure of near work, were calculated. Diopter hours for all subjects were significantly higher on weekdays (14.73 ± 4.67 dh) compared to weekends (11.90 ± 4.84 dh, p = 0.05). 94 ± 1.85% of near and intermediate viewing distances were recorded when the subjects were exposed to mesopic and indoor photopic light levels (<1000 lux), and 80.03 ± 2.11% during periods of sedentary physical activity (<320 counts per minute). Subjective reports of time viewing near and intermediate distances significantly overestimated objective measures (p = 0.002). The RangeLife was shown to provide reliable measures of viewing distance, and can be further utilized to understand potential influences of viewing behaviors on refractive error.

Improved indoor lighting improved healthy aging at home - an intervention study in 77-year-old Norwegians.

Introduction: Healthy aging and good quality of life is important to allow older people to live at home. Lighting is a significant environmental attribute promoting visual, physical, and mental health. Due to normal visual age changes, older people need more light, but improving indoor lighting levels receives little attention.Objective: To investigate the impact of improved home lighting on abilities to perform activities of daily living (ADLs) and quality of life in healthy older people.Methods: Sixty healthy 77 years old living at home participated during the 4-month dark winter period. In the intervention group (IG, n=30), the living room lighting was optimized by providing lamps and a basic control system with three preset levels (normal, medium, low). Participants chose the light level and kept a diary. No change was implemented for the control group (CG, n=30). A questionnaire measured self-reported visual and general health and ability to perform ADL in regards to lighting before and after the intervention in both groups.Results: In the IG, lighting levels significantly improved self-assessed lighting levels, abilities to perform ADLs, and read and write in the living room (all p<0.03). In the CG the only change was a deterioration in performing ADLs (p<0.05). The difference in change was significant between the IG and CG (all p<0.02). “Normal” lighting was the preferred level and increased comfort and well-being. The IG also resumed visually demanding tasks, and acknowledged that avoiding these tasks were mainly due to poor lighting.Conclusions: Good vision is essential in promoting healthy aging at home and require adequate lighting. This can easily be achieved using a basic light system. Adopting to higher lighting levels evolves quickly. Our results suggest that improved quality of light could improve quality of life, and lighting should be included as a factor promoting healthy aging at home.

An evaluation of classroom-illumination: a critical requirement for effective designing and construction of naturally-illuminated schools in Nigeria

Indoor lighting-levels (illuminances) of 180 classrooms in 60 public [primary and secondary] schools located in all six geopolitical zones of Nigeria, were experimentally investigated 12 times under three different sky-conditions ['clear', 'partly-clear' and 'overcast'] using the Hagner digital lux-meter. The analysed empirical-data were: 'Mean indoor illuminance for tasks on desks' tops near windows exposed to direct sunlight and/or higher illumination(Ld(DSL))' ranging from 1,243 lux-4,486 lux, 'Mean indoor illuminance for tasks on desks' tops near windows exposed to indirect sunlight and/or lower illumination(Ld(ISL))' ranging from 674 lux-2,987 lux, 'Mean indoor illuminance for tasks on desks' tops at Center of Classroom(Ld(CrC))' ranging from 101 lux-449 lux and 'Mean indoor illuminance for tasks on boards(Lb)' ranging from 110 lux-494 lux. Three globally recommended standards' ['CIE-ISO', 'IESNA', and 'EN'], values [of minimal/optimal lighting-levels for classroom-activities like 'reading on the blackboard' (Lsb 500 lux) and 'writing, drawing and reading on desks' (Lsd = 300 lux)]; and the follow-up statistical-analyses reveal 'excessive solar irradiation' and/or 'inadequate illumination' in the classrooms.

Shedding Some Light in the Dark - Validity of Using Satellite Measurements to Estimate Light at Night Exposure

Background: Exposure to light at night (LAN) can perturb the biological clock and affect sleep and health. Several epidemiological studies have evaluated LAN levels measured by satellites, but the validity of this measure as a proxy for personal LAN exposure is unclear. Also, outdoor light at night measured by satellites displays higher levels in urban environments, which means that this measure could potentially represent a proxy for other, likely urban, environmental exposures.Objectives: We evaluated correlations of satellite-assessed LAN with measured bedroom light levels, and explored correlations with other environmental exposures, in particular air pollution, green space and area-level socio-economic position.Methods: We compared satellite measurements with nighttime bedroom measurements in illuminance (Lux) in 251 children and additionally evaluated correlations to other urban exposures such as air pollution, area-level socio-economic position and surrounding green in 3021 children.Results: Satellite-measured LAN levels (nanoW/cm2/sr) were not correlated with bedroom-measured Lux (Spearman corr. coeff. -0.02). There was a weak correlation if parents reported influence of outdoor light on indoor light levels (rS&amp;#61;0.31). Satellite-measured LAN levels were correlated to air pollution (rS&amp;#61;0.76 with NO2, rS&amp;#61;0.71 with PM10) surrounding green (rS&amp;#61;-0.68 for green space within 1km of the home), and weakly to area-level socio-economic position (rS&amp;#61;0.24).Conclusions: Our study results indicate that outdoor satellite-assessed LAN levels are not a good proxy for nighttime personal exposure in bedrooms, but rather a proxy for other urban exposures. Studies planning to evaluate potential risks from LAN should therefore consider modifying factors such as curtains and indoor lighting and perform indoor or personal measurements to validate their exposure proxies. Other environmental exposures should be accounted for in epidemiological investigations.

Can houseplants improve indoor air quality by removing CO2 and increasing relative humidity?

High indoor CO2 concentrations and low relative humidity (RH) create an array of well-documented human health issues. Therefore, assessing houseplants’ potential as a low-cost approach to CO2 removal and increasing RH is important. We investigated how environmental factors such as ‘dry’ ( 0.30 m3 m−3) growing substrates, and indoor light levels (‘low’ 10 μmol m−2 s−1, ‘high’ 50 μmol m−2 s−1, and ‘very high’ 300 μmol m−2 s−1) influence the plants’ net CO2 assimilation (‘A’) and water vapour loss. Seven common houseplant taxa—representing a variety of leaf types and sizes—were studied for their ability to assimilate CO2 across a range of indoor light levels. Additionally, to assess the plants’ potential contribution to RH increase, the plants’ evapo-transpiration (ET) was measured. At typical ‘low’ indoor light levels, ‘A’ rates were generally low (< 3.9 mg h−1). Differences between ‘dry’ and ‘wet’ plants at typical indoor light levels were negligible in terms of room-level impact. Light compensation points (i.e. the light level where the CO2 assimilation equals zero) were in the typical indoor light range (1–50 μmol m−2 s−1) only for two studied Spathiphyllum wallisii cultivars and Hedera helix; these plants would thus provide the best CO2 removal indoors. Additionally, increasing indoor light levels to 300 μmol m−2 s−1 would, in most species, significantly increase their potential to assimilate CO2. Species which assimilated the most CO2 also contributed most to increasing RH.

Energy analysis of zero energy schools: the case study of child’s asylum in Greece

ABSTRACTSchool buildings constitute a rather special case of buildings when it comes to energy performance since the operational costs for heating, cooling and ventilation are usually far less important than the achieved thermal comfort, indoor air quality and lighting levels due to the very sensitive subject of students’ health, well-being and ability to attend lessons Moreover, there is a significant margin for improvement in school buildings’ energy performance and indoor environmental quality. The aim of the present paper is to present the design and energy technologies of a zero energy school in Greece. The energy performance of the zero energy building is analysed. A reduction of the energy demand by almost 68% is accomplished while a significant improvement of the indoor thermal comfort is achieved through the zero energy building design.