Window Film Research Articles

A natural environmental chamber study on the emissions and fate of organophosphate esters in the indoor environment

In this study, we investigated the emission and fate of 9 organophosphate esters (OPEs) from a natural environment chamber, in which three environment matrices (i.e., air, dust, and window film samples) as well as three decoration materials (i.e., laminate flooring, latex paint, and nonwoven paper) were collected within gradient variation of room temperature and relative humidity. ΣAlkyl-OPEs and ΣCl-OPEs were the predominant classes in the three environment matrices, accounting – on average – for 98.7%, 99.8% and 99.3% of ΣOPEs in indoor dust, air and window film, respectively. TBOEP was the most abundant OPE in air, dust, and laminate flooring, respectively, while tris (2-chloro-isopropyl) phosphate (TCIPP) and tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) in nonwoven paper and latex paint, respectively. The results showed that higher room temperature expedited the emission of OPEs to indoor air. However, the room temperature and relative humidity had no effect on the levels of OPEs in dust. The OPEs equilibrium time in indoor environment may be dependent on room temperature and relative humidity. The area specific emission rates (SERs) of the three materials were calculated, and an optimal expression based on the concept of mass balance model was constructed, preliminarily revealing a general relationship between OPEs source and sink effects in indoor environment.

Highly Transparent, Colorless Optical Film with Outstanding Mechanical Strength and Folding Reliability Using Mismatched Charge‐Transfer Complex Intensification

AbstractThe development of flexible displays and electronics is hindered by the disadvantages of polymeric window films, such as low mechanical strength, poor optical properties, and lack of folding and rolling reliability. To overcome these critical limitations, a novel colorless polyimide window film is prepared in this study using the concept of charge‐transfer complex (CTC) intensification. The resulting window film has a tensile modulus of 8.4 GPa, total transmittance of ≈90%, and yellow index below 3, which is the best recorded balance between mechanical strength and optical properties for a highly flexible optical film. Unlike commercially available optical‐grade engineering plastic films and glass substrates, the prepared window film has both pencil hardness grade over 2H and folding reliability over 200 000 folding/unfolding cycles. These remarkable properties are attributed to the unique supramolecular structure with multiple hydrogen bonding and salt complexation interactions, which exhibits CTC intensification. The CTC intensification mechanism is also proposed in this study.

Thermo-optical performance of molecular solar thermal energy storage films

Due to their potential for solar energy harvesting and storage, molecular solar thermal energy storage (MOST) materials are receiving wide attention from both the research community and the public. MOST materials absorb photons and convert their energy to chemical energy, which is contained within the bonds of the MOST molecules. Depending on the molecular structure, these materials can store up to 1 MJ/kg, at ambient temperature and with storage times ranging from minutes to several years. This work is the first to thoroughly investigate the potential of MOST materials for the development of energy saving windows. To this end, the MOST molecules are integrated into thin, optically transparent films, which store solar energy during the daytime and release heat at a later point in time. A combined experimental and modeling approach is used to verify the system's basic functionality and identify key parameters. Multi-physics modeling and simulation were conducted to evaluate the interaction of MOST films with light, both monochromatic and the entire solar spectrum, as well as the corresponding dynamic energy storage. The model was experimentally verified by studying the optical response of thin MOST films containing norbornadiene derivatives as a functional system. We found that the MOST films act as excellent UV shield and can store up to 0.37 kWh/m2 for optimized MOST molecules. Further, this model allowed us to screen various material parameters and develop guidelines on how to optimize the performance of MOST window films.

Distribution of Polycyclic Aromatic Hydrocarbons in Indoor/Outdoor Window Films and the Indoor Film/Air Partition of Northeastern Chinese College Dormitories

Distribution of Polycyclic Aromatic Hydrocarbons in Indoor/Outdoor Window Films and the Indoor Film/Air Partition of Northeastern Chinese College Dormitories

Aspects of optical and thermal performances in flexible perovskite solar cells made of nanomaterials with potential for development of vehicle-integrated photovoltaics

In the near future, electric vehicles will be a primary type of transports used. They are noise- and emission-free, with the ability to enable zero-emission use if they are charged using renewable energy. To offer this clean energy at the point of consumption, vehicle-integrated photovoltaic (VIPV), or photovoltaic (PV) that is incorporated into the body of the car, is a revolutionary approach. This capability might be explained as being able to extend the operating range and to be free of charge when out in the field. Thus, solar cells for this application must be very efficient, lightweight, and compatible with curved surfaces. Until now, development has been limited to the roof area of a car and has largely relied on crystalline-based solar cells. However, an automobile has a greater surface area that might theoretically be used to mount the solar cells. For example, transparent areas such as vehicle windows are considered because it may be possible to employ partially transparent flexible solar cells such as perovskite solar cells. The purpose of this research is to determine the viability of using flexible perovskite solar cells in automotive window film applications by comparing their transmittance and reflectance to films that meet automotive window film specifications in Thailand. While thermal efficiency is determined by heat gain and thermal transmission. Additionally, we also demonstrate how the nanoparticles utilized in the recent development of perovskite solar cells can be employed to enhance their optical and thermal properties.

Adjustable Internal Shading for Home Office Daylighting in Tropical Climates

Home-based workspaces have considerably increased all over the world. Besides, the recent outbreak of the COVID-19 disease forced many people to work from their homes. However, existing residential apartment buildings (ERABs) had been designed for accommodation but not for office works. Low-quality visual environments in ERABs, which have no shading controls on their windows, are evident in tropical climates with extremely high solar radiation. Thus, interior retrofit is significant to provide visual comfort for users in ERABs with low flexibility for modification of their facades. Different interior design variables were simulated by the Radiance-based program to analyse daylighting in a closed-plan room. Before the simulation experiments, field measurement of daylight was performed under a tropical sky to validate the results, and the findings revealed significant Pearson correlations. This paper showed that ERABs are confronting extremely high indoor daylight quantity, up to 10,228 lx, and low quality with intolerable glare. An adjustable model of internal shading, including an integrated Venetian blind with a horizontal light shelf and the window films, was proposed to improve quantitative and qualitative performances of daylighting in tropical regions. This dynamic model could be adjusted to various positions based on daylighting conditions in the buildings. By comparing the simulation results of this model with the base model, indoor illuminance levels could successfully reduce from 32% to 86%; Illuminance Uniformity Ratio (IUR) and Target Daylight Illuminance (TDI) significantly improved up to 180% and 300%, respectively; Daylight Glare Probability (DGP) and CIE Glare Index (CGI) changed from intolerable to imperceptible status. Accordingly, the proposed model can considerably improve daylight quantity and quality in the test room during different times. This study concludes that the dynamic model of internal shadings could provide efficient daylighting, by decreasing the extremely high indoor illuminance and glare in the ERABs in tropical climates.

Silicon nanostructure-doped polymer/nematic liquid crystal composites for low voltage-driven smart windows

In this work, two silicon nanostructures were doped into polymer/nematic liquid crystal composites to regulate the electric-optical performance. Commercial SiO2 nanoparticles and synthesized thiol polyhedral oligomeric silsesquioxane (POSS-SH) were chosen as the dopants to afford the silicon nanostructures. SiO2 nanoparticles were physically dispersed in the composites and the nanostructure from POSS-SH was implanted into the polymer matrix of the composites via photoinduced thiol-ene crosslinking. Scanning electron microscopy results indicated that the implantation of POSS microstructure into the polymer matrix was conducive to obtaining the uniform porous polymer microstructures in the composites while the introduction of SiO2 nanoparticles led to the loose and heterogeneous polymer morphologies. The electric-optical performance test results also demonstrated that the electric-optical performance regulation effect of POSS microstructure was more obvious than that of SiO2 nanoparticles. The driving voltage was reduced by almost 80% if the concentration of POSS-SH in the composite was nearly 8 wt% and the sample could be completely driven by the electric field whose voltage was lower than the safe voltage for continuous contact (24 V). This work could provide a creative approach for the regulation of electric-optical performance for polymer/nematic liquid crystal composites and the fabrication of low voltage-driven PDLC films for smart windows.

Puncture Impact Test on Glass Plate Fitted with Shatterproof Window Film

Puncture Impact Test on Glass Plate Fitted with Shatterproof Window Film

Low-Emissivity Window Films as an Energy Retrofit Option for a Historical Stone Building in Cold Climate

Low-emissivity (low-E) window films are designed to improve the thermal comfort and energy performance of buildings. These films can be applied to different glazing systems without having to change the whole window. This makes it possible to apply films to windows in old and historical buildings for which preservation regulations often require that windows should remain unchanged. This research aims to investigate the impacts of low-E window films on the energy performance and thermal comfort of a three-story historical stone building in the cold climate of Sweden using the simulation software “IDA ICE”. On-site measurements were taken to acquire thermal and optical properties of the windows. This research shows that the application of the low-emissivity window film on the outward-facing surface of the inner pane of the double-glazed windows helped to reduce heat loss through the windows in winter and unwanted heat gains in summer by almost 36% and 35%, respectively. This resulted in a 6% reduction in the building’s annual energy consumption for heating purposes and a reduction in the percentage of total occupant hours with thermal dissatisfaction from 14% (without the film) to 11% (with the film). However, the relatively high price of the films and low price of district heating results in a rather long payback period of around 30 years. Thus, the films seem scarcely attractive from a purely economic viewpoint, but may be warranted for energy/environmental and thermal comfort reasons.

Enhanced visible and tunable infrared transmittance of W-doped VO2/SiO2/PVP composite films for smart windows

As a thermochromic material, vanadium dioxide (VO 2 ) has great application potential in smart windows. It has always been the focus of research to improve the visible light transmittance (T lum ) and solar modulation ability ( Δ T s o l ) while reducing the phase transition temperature (T c ) of VO 2 . To achieve this goal, tungsten-doped VO 2 nanoparticles (W-VO 2 NPs) with a T c of 34 °C were used to form composite films with polyvinylpyrrolidone (PVP) by a simple method. High Δ T s o l of 14.2% was obtained at the optimized volumetric concentration of W-VO 2 and film thickness. The W-VO 2 /SiO 2 /PVP composite films were proposed to further improve T lum and Δ T s o l . Compared with the W-VO 2 /PVP composite film with the same thickness and volumetric concentration of W-VO 2 , T lum of the film is increased by 19.3% (from 54.5% to 65%) with the introduction of SiO 2 microspheres, while the Δ T s o l is maintained satisfactorily at 12.6%. This is mainly due to the monolayer dispersed SiO 2 microspheres providing optical pathways in the film, which greatly improves T lum with a slight sacrifice of Δ T s o l . Indoor temperature of a scale-model room with W-VO 2 /SiO 2 /PVP film-coated glass was 9.1 °C lower than that with blank glass due to the isolation effect of metallic W-VO 2 on near-infrared radiation. This work provides a new strategy for promoting the development of VO 2 thermochromic smart windows. • Effect of W-VO 2 volumetric concentration and thickness of film on thermochromic performance were studied and optimized. • Comprehensive thermochromic performance was enhanced by the local surface plasma effect of W-VO 2 . • The improvement of solar modulation ability by increasing volumetric concentration of W-VO 2 nanoparticles is limited. • SiO 2 microspheres were introduced as optical pathways to enhance transmittance of visible light.

Transparent radiative cooling films containing poly(methylmethacrylate), silica, and silver

Window is the least energy-efficient part of buildings or cars; however radiative cooling, as an efficient energy-zero technology, is rarely used in window films of buildings or cars. Therefore, we in this work fabricated a transparent dual-layer film for daytime radiative cooling, which contained a layer of polymethyl methacrylate (PMMA) uniformly mixed with modified silica nanoparticles (SiO2 NPs) and a layer of silver. The dispersion of the modified SiO2 NPs in PMMA was notably improved through in-site grafting PMMA, which resulted in a high transparency of the radiative cooling film even at a high filling fraction of SiO2 (20 wt%). Owing to the strong broadband IR absorbance/emittance (εAW = 94.3%) and high sunlight reflectance (ρ ≈ 50%), the dual-layer film possessed a high cooling capacity and could achieve an average temperature drop of 1.4 °C than pure PMMA film in the daytime outdoor cooling measurement. In the simulated automotive cooling test, the dual-layer film cooled the interior space up to 6 °C below ambient temperature during peak solar hours. The excellent optical property and cooling capability exhibit a promising application of building and car windows for cooling their interior spaces.

IMPACT OF INTERNAL SHADING CONTROLS ON EFFICIENT DAYLIGHTING IN HOME-OFFICE WORKSPACES IN TROPICAL CLIMATES

Home office workspaces have significantly grown in residential sectors throughout the world. Nowadays, many people worldwide are forced to work from their housing units due to the outbreak of the COVID-19 pandemic. However, the existing residential buildings were only designed for living activities, not for desk-related tasks. This is more critical in tropical regions with the overabundance of indoor daylight and lack of external shadings on existing buildings. Despite the limitations for modifying the external facades, interior retrofit plays a major role in improving visual environments. Daylighting performances of various configurations, including internal shading devices, interior surfaces, and window films, were experimented with the Radiance-IES program. A field measurement of daylight was conducted in a home office room under the Malaysian tropical sky to validate the simulated results. This research proved that the existing residential buildings in the tropical climates had poor daylighting performance where the mean indoor illuminance could be over 10,000 lx. The combination of a light shelf, a partial blind, and the tinted window film could effectively 85% alleviate the excessive indoor daylight level. This configuration recorded a significant improvement in Useful Daylight Zone (around 300%), and Daylight Glare Probability was considerably reduced from 0.46 to 0.34.

Mist CVD of vanadium dioxide thin films with excellent thermochromic properties using a water-based precursor solution

Mist chemical vapor deposition (mist CVD), which is capable of producing oxide films over large areas at a high productivity and low cost, has been proposed as a fabrication method for VO2 thin films for smart windows. However, the thermochromic properties of the VO2 films previously prepared by mist CVD are not sufficient for application in smart windows. In this study, to obtain a high-quality VO2 film, we investigated the effects of the solvent of the precursor solution on the resulting film in mist CVD. Films consisting of a single phase of VO2 were obtained when a water-based precursor solution was used. In contrast, V2O3 films are formed when a methanol-based precursor solution is used. The VO2 film deposited from water solution exhibited high visible transmittance along with a large change in the infrared transmittance with temperature change. The high quality of the VO2 film indicates that mist CVD is an effective method for the fabrication of VO2-based smart windows.

Acid Solution Processed VO2-Based Composite Films with Enhanced Thermochromic Properties for Smart Windows.

As a typical thermochromic material, VO2 coatings can be applied to smart windows by modulating the transmission of near infrared (NIR) light via phase transition. However, the inherent undesirable luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of pure VO2 impede its practical application. In order to solve this problem, the porous VO2 based composite film was prepared by magnetron sputtering and subsequent acid solution process with Zn2V2O7 particles used as a sacrificial template to create pores, which showed excellent Tlum (72.1%) and enhanced ΔTsol (10.7%) compared with pure VO2 film. It was demonstrated that the porous structure of the film caused by acid solution process could improve the Tlum obviously and the isolated VO2 nanoparticles presented strong localized surface plasmon resonance (LSPR) effects to enhance the ΔTsol. Therefore, this method will provide a facile way to prepare VO2 based films with excellent thermochromic performance and thus promote the application of the VO2 based films in smart windows.

Passive cooling designs to improve heat resilience of homes in underserved and vulnerable communities

Disadvantaged communities face a growing threat to staying safe during heat waves, especially during coincident power outages. This study develops a methodology to evaluate the effectiveness of passive cooling measures (those that operate without power) to improve residential building heat resilience. Building performance is simulated for representative homes and on district scales in two disadvantaged communities in Fresno, California. Eleven passive measures are evaluated using four heat resilience metrics with and without grid power. Results show performance of the mitigation measures varies by building characteristics, surrounding environment, and power scenario. The two most effective measures were installing solar-control window films and adding roof insulation. For pre-1978 single-family homes, these two measures can reduce unmet degree-hours (UDH) indoors by 12% and 11% respectively without grid power, or 28% and 37% with grid power. Their respective UDH reductions at district scale typically range 8% — 20% and 4% — 12% without grid power, or 14% — 44% and 8% — 51% with grid power. Top floors have higher overheating risk than lower floors during extreme heat events with coincident power outages. Natural ventilation can help, reducing UDH by 21% — 26%. The methodology and findings from this study can help cities, communities, and utilities develop effective and targeted strategies to promote greater residential heat resilience.

Presence of organophosphate flame retardants (OPEs) in different functional areas in residential homes in Beijing, China

The production and application of organophosphate esters (OPEs) have dramatically increased in recent years due to their use as a replacement for brominated flame retardants. In this study, 13 OPEs (Σ13OPEs) were analyzed in indoor air samples from kitchens and living rooms in 14 residential homes in Beijing, China. The concentrations of Σ13OPEs in kitchen air samples (mean: 13 ng/m3) were significantly (p < 0.05) higher than in living room air samples (5.0 ng/m3). In addition, paired window surface organic film samples were collected and analyzed to investigate film-air partitioning, exhibiting a mean concentration of Σ13OPEs of 4100 ng/m2. The congener profiles showed that tris(2-chloroisopropyl) phosphate (TCPP) was the predominant compound in both window film samples (48%) and the corresponding indoor air sample (56%). The estimated daily intakes (EDI) of OPEs via indoor air inhalation were 2.8 and 1.4 ng/kg/day for infants and adults, respectively, both of which are below the reference dose values (RfDs). Overall, these findings indicate that OPEs in the indoor air environment of residential homes in Beijing are not likely to pose a health risk to the general population.

Energy‐Saving Windows: Photonic Multilayer Structure Induced High Near‐Infrared (NIR) Blockage as Energy‐Saving Window (Small 29/2021)

A highly transparent window film with high near-infrared (NIR) reflection is systemically designed for energy-saving windows. A photonic multilayer structure combining TiO2 back reflector with TiO2/Ag/TiO2 structure can effectively block solar energy in NIR without sacrificing visible transmittance. The results presented in article number 2100654 by Kwang Ho Kim, Jong-Lam Lee, and co-workers can be used as a guideline of design for various energy-saving applications.

Effects of Window Films in Thermo-Solar Properties of Office Buildings in Hot-Arid Climates

The electricity consumption in residential/office buildings corresponded to 45% of the total annual electricity demand in hot-arid climates. This accounted for 27.2 TWh of electricity consumption with 14.2 MWh/capita/year in Kuwait. In this research, four offices in an educational building were equipped with a meteorological data logging system using temperature, humidity, and illuminance sensors. All four offices had double-glazed windows. Moreover, two offices were equipped with two types of commercially available window films. Two million data were stored in iCloud using Wi-Fi and an Internet of Things (IoT) system for the 3 months of June, July, and August 2019. Here, histograms and the kernel density estimation (KDE) of temperature/humidity were analyzed and compared for the two offices with/without 3M Neutral 20 window films. Two floors of the same building consisting of 31 offices were also modeled and simulated to study energy saving and CO2 footprint reduction using various window films. The results of simulations for the month of July 2019 using SOL 101 and SOL 102 window films, respectively, showed that about 250 kg and 255 kg of production of CO2 could be reduced and energy saving counted for 416 and 422 kWh. Measurements from offices with 3M Neutral 20% and 3M Neutral 70% window films for the month of July 2019 indicated that the carbon footprint could be reduced by about 82 kg and 0.43 kg and energy saving counted for 147.11 and 0.71 kWh, respectively. It was observed that an annual energy saving and CO2 footprint reduction of 2.76% could be achieved using window films in a hot-arid climate.

Pengaruh Prosentase Kepekatan Kaca Film Terhadap Distribusi Termal dan Pencahayaan Kabin Kendaraan

Window film is a thin layer on car glass that functions as a medium for repelling sunlight. This study aims to determine the effect of percentage of window film density on the thermal and lighting distribution of the vehicle cabin. This research was conducted using a room model measuring 50x50x30 cm. The variation of window film uses two brands of Ultima and 3M, with the respective percentages of 40% and 60%. When the experiment was carried out in an open space, the irradiation process was carried out for 2 hours using the sun's rays at 11.00 - 13.00 WIB in each variation. Temperature measurement uses a digital thermometer on the surface of the coated glass (T1) and indoors (T2), while the measurement of light intensity uses a lux meter that is placed outdoors (I1) and indoors (I2). Data analysis using the equations of temperature rate and effectiveness of heat and light reduction. The results showed that the difference in the percentage of glass film density affected the rate of heat transfer and the intensity of the light entering the room. The heat transfer rate tends to increase in Q1 with a value of 58375.61 joules, and decrease in Q2 with a value of 1160.46 joules in the variation of 3M glass film brands with a 60% concentration level. Meanwhile, the average temperature increase rate is 0.002 ℃ / minute for all variations of window film brands with a light intensity of 0.007 - 0.008 lux.&#x0D; &#x0D; Keywords : window film, temperature rate, light intensity, heat transfer.

Phthalates in glass window films in university dormitories in Beijing, China, and exposure implications

Phthalate concentrations were measured in glass window films in 145 dormitories at 13 universities in Beijing, China, from May to December 2019. We analyzed phthalate characteristics, examined possible phthalate sources, compared concentration differences between female and male dormitories and between sunny and shaded dormitories, and estimated the phthalate intake via dust ingestion, inhalation, and dermal absorption through direct air-through-skin pathways using Monte Carlo simulations. DCHP and DEHP were the most predominant phthalates in the window films, followed by DnBP, with median concentrations one to two orders of magnitude higher than those of the other phthalates. The contributions of DnBP, DCHP and DEHP to the total phthalate concentration were in the range of 2.2–45.9%. Phthalates in window films might have four indoor sources. The concentrations of six phthalates and ΣPAEs were higher in female dormitories than in male dormitories. Most phthalates showed no significant difference between sunny and shaded dormitories because the effects of temperature and photodegradation may have negated one another. The median phthalate intake ranged from 0.54 ng/(kg·day) to 4.61 μg/(kg·day). DMP and DEP exposures were the highest, followed by those of DiBP and DnBP. The intakes of 11 phthalates were higher for female students. Dermal absorption was the main exposure pathway of DMP, DEP, DiBP, DnBP, DMEP, DPP, DHP, and BBzP (contribution: 48.7–72.9%). For the other phthalates, dust ingestion was the main pathway (contribution: 64.5–97.5%).