energies Article
Development of Window-Mounted Air Cap Roller Module Heangwoo Lee 1 1 2
*
ID
and Janghoo Seo 2, *
ID
Institute of Green Building and New Technology Mirae Environment Plan, Seoul 01905, Korea;
[email protected] School of Architure, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Korea Correspondence:
[email protected]; Tel.: +82-2-910-4593
Received: 6 July 2018; Accepted: 19 July 2018; Published: 21 July 2018
Abstract: While previous research has shown the use of attachable air-caps on windows to efficiently reduce a building’s energy consumption, the air-caps considered had to be attached to the entire window’s surface, thus limiting the occupants’ view and creating the inconvenience of needing to detach and attach the air-caps. In this study, a window-mounted air-cap roller module using Velcro tape that may be easily attached, detached, and rolled up or down was developed and performance tested in a full-scale test bed. It was found that as the area of the air-caps attached on a window increased, the required indoor lighting energy increased. However, the window insulation improved, thus reducing the cooling and heating energy needed. Attaching the air-caps to the entire window surface effectively reduced the building’s energy consumption, but views through the window may be disturbed. Thus, the developed window-mounted air-caps enable an occupant to reduce the building energy consumption and maintain their view according to their need. The findings of this study may contribute to a reduction in building energy consumption without sacrificing a pleasant indoor environment. Further studies may be needed to verify their efficacy under varying indoor and outdoor conditions. Keywords: air cap; roller module; energy saving; performance evaluation; building envelope
1. Introduction The concept of net zero energy buildings has been extensively examined; the concept that the power generation from new renewable energy resources offsets the total energy consumption of the building, thus achieving net-zero energy consumption [1–3]. Although many studies contributed to the development of new and renewable energy resources to counterbalance the total energy spent in the building, net zero energy buildings are mostly impossible without reduced energy consumption of the building itself. The “2015 Renewable Energy Data Book”, published by the United States Department of Energy, reported that energy consumption by buildings accounted for 39.8% of the overall energy consumption in the United States [4]. It also predicted that the energy consumption of the buildings would continue to increase. The energy usage of buildings for space heating, lighting, and cooling is as high as 20.8%, 11.3%, and 10.0% of the total energy usage in the United States, respectively [5]. Therefore, there is an increased requirement to develop technologies and methods to reduce the energy consumed by buildings. Further, high energy consumption is related to the poor insulation of building skins, especially that of windows. Various studies have been conducted to investigate potential approaches for improving the thermal performance of windows, including the use of double skins [6–15], phase change materials (PCM) [16–22], window blinds [23–32], awnings [33–35], and light shelves [36–41]. Although several of these apparatuses may be efficiently used to reduce the energy consumption of the buildings, they often have high installation costs or are difficult to be Energies 2018, 11, 1909; doi:10.3390/en11071909
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applied to the existing buildings. Air caps, originally developed by the Sealed Air Corporation [42] [42] as a packaging material, comprise a regular pattern of air pockets that are sealed between two as a packaging material, comprise a regular pattern of air pockets that are sealed between two sheets sheets of polyethylene film and have been depicted to improve window insulation. In previous of polyethylene film and have been depicted to improve window insulation. In previous studies, air studies, air caps were attached to the entire window surface [43–45], which may have efficiently caps were attached to the entire window surface [43–45], which may have efficiently improved the improved the insulation performance of the window; however, this may disturb the view through insulation performance of the window; however, this may disturb the view through the window and the window and increase the amount of energy required to ensure indoor lighting. Additionally, increase the amount of energy required to ensure indoor lighting. Additionally, water or double-sided water or double-sided adhesive tape was used to adhere the air caps [43,44], which caused problems adhesive tape was used to adhere the air caps [43,44], which caused problems while attaching and while attaching and detaching the air-caps. In this study, a window-mounted air cap roller module detaching the air-caps. In this study, a window-mounted air cap roller module was developed for easy was developed for easy attachment, detachment, and adjustment of the air caps. A full-scale test bed attachment, detachment, and adjustment of the air caps. A full-scale test bed was used to verify the was used to verify the effectiveness of the module in reducing the energy consumption that is effectiveness of the module in reducing the energy consumption that is required for heating, lighting, required for heating, lighting, and cooling a building. and cooling a building. 1.1. Literature Review Research on Air Caps and Their Specifications 1.1. Literature Review Research on Air Caps and Their Specifications According to the information provided by the manufacturer [42], air cap pockets are generally According to the information provided by the manufacturer [42], air cap pockets are generally circular and their dimensions vary depending on the thickness of the air-filled layer, as shown in circular and their dimensions vary depending on the thickness of the air-filled layer, as shown in Table 1. In this study, Type 2 air caps with 10-mm diameter circular air-filled pockets were used. This Table 1. In this study, Type 2 air caps with 10-mm diameter circular air-filled pockets were used. choice was based on a previous study, in which the thermal performance of a window was improved This choice was based on a previous study, in which the thermal performance of a window was using air caps [43]. improved using air caps [43]. Table 1. Air cap specifications provided by the manufacturer. Table 1. Air cap specifications provided by the manufacturer.
Type
D (Diameter of D (Diameter of Type Air Layer) Air Layer)
1 2 3 4 5
1
t (Thickness of t (Thickness of Coating Layer) Coating Layer)
0.2 mm
10 mm
0.2 mm
10 mm
0.4 mm
2 3 4 5
Air Cap Section
Air Cap Section
0.4 mm
20 mm
20 mm
25 mm 25 mm
0.6 mm 0.6 mm
30 mm
30 mm
Table22presents presentsaasummary summary of of previous previous work Table work improving improving building buildinginsulation insulationby byimplementing implementingair caps. In previous studies, researchers suggested attaching air caps directly onto the glass air caps. In previous studies, researchers suggested attaching air caps directly onto the glasssurfaces surfacesor windows to achieve an air-tight fit and insulation performance. However, attaching orframes framesof of windows to achieve an air-tight fitimprove and improve insulation performance. However, air caps directly onto a window may impair viewing through the window, which is its original attaching air caps directly onto a window may impair viewing through the window, whichfunction. is its Moreover, attaching air caps onto a window themay amount of natural light entering the original function. Moreover, attaching air capsmay ontodecrease a window decrease the amount of natural building, thereby reducing the indoor illumination and increasing the energy demand for light entering the building, thereby reducing the indoor illumination and increasing thelighting. energy demand for lighting.
Table 2. Previous studies on air caps for the improvement of window insulation performance.
Table 2. Previous studies on air caps for the improvement of window insulation performance. Author (year)
Author (year) Lee et al. (2015) [43]
Materials for Attachment of Air Capsfor Materials
Attachment of Water or Air Caps double-sided adhesive tape
Hwang et al. (2015) [44]
Lee et al. (2015) [43]
Lee et al. (2017) [45]
Hwang et al. (2015) [44]
Lee et al. (2017) [45]
Parts to Which Air Caps are Attached
Parts to Which Air Caps are Attached Glass surface or window frame
Area of Window to Which Air Caps Area of are Attached
Window to Which Air Caps Entire aresurface Attached
Consideration of Views Through Windowsof Consideration Depending on Air Views Through Cap Coverage
Windows Depending on Air Not considered Cap Coverage
Water or Water double-sided adhesive tapeand Linear magnet
Glass surface of Glass surface or window window frame
Entire surface
Not considered
insulation tape
Window frame
Glass surface of window
Entire surface
Not considered
Water
Linear magnet and insulation tape
Window frame
Entire surface
Not considered
Entire surface
Not considered
Entire surface
Not considered
1.2. Appropriate Indoor Temperature and Illumination Standards for Performance Evaluation
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1.2. Appropriate Indoor Temperature and Illumination Standards for Performance Evaluation Indoor temperature and illumination are factors that determine the pleasantness of an indoor space. Maintaining them at a constant level contributes to a reduction in total building energy consumption by preventing unnecessary energy consumption for cooling, heating, and lighting [46]. Therefore, setting appropriate standards for indoor temperature and illumination is important in controlling cooling and heating devices and lighting. A summary of the appropriate indoor temperature and illumination standards for various countries is presented in Tables 3 and 4. Based on these standards, the performance evaluation in this study was conducted for maintaining the summer and winter indoor temperature standards of 26 ◦ C and 20 ◦ C, respectively. The appropriate indoor illumination standard was determined as 500 lx [35]. The reasons for selecting this indoor illumination standard for the performance evaluation in this study were the following. Upon examining the illumination standards of the United States, Japan, and Korea, the values of 500 and 600 lx were found to be used interchangeably as the illumination for a “normal” task grade. In the cases of Japan and South Korea, 600 lx is designated as the maximum allowed illumination. In light of this, the 600 lx value was excluded as an appropriate indoor illumination standard. Therefore, this study set 500 lx as the appropriate indoor illumination standard and proceeded to carry out the performance evaluation under this condition. Table 3. Appropriate indoor temperature standard. Standard
Summer (◦ C)
Winter (◦ C)
ANSI/ASHRAE Standard 55-2013 (USA) [47] ISO Standard (Europe) [48]
23.0–26.0 23.0–26.0
20.0–23.5 20.0–24.0
Table 4. Appropriate indoor illumination standard.
Task Grade
Minimum Allowed Illumination (lx)
Standard Allowed Illumination (lx)
Maximum Allowed Illumination (lx)
IES (USA) [49]
Normal Simple
500 200
750 300
1000 500
JIS Z 9110 (Japan) [50]
Normal Simple
300 150
500 200
600 300
KS A 3011 (Republic of Korea) [51]
Normal Simple
300 150
400 200
600 300
Reference Standards
2. Proposal and Performance Evaluation Methods 2.1. Proposal of Window-Mounted Air Cap Roller Module The proposed window-mounted air cap roller module shown in Figures 1–3 allows a user to roll the air cap sheets up or down to vary the window area to which the air caps are attached in accordance with the desired view and illumination through the window. However, decreasing this area may reduce the insulation performance of the windows, resulting in an increase in the building’s energy consumption. To overcome this limitation, the window-mounted air cap roller module was attached to the window frame. This was based on the findings of a previous report, which indicated that the insulation performance of a window was improved more when the air caps were attached to the window frame than when they were attached to the glass surface of the window [43]. Velcro™ tape and dual-sided insulation tape were used to attach the air caps to the window frame to improve the insulation and allow easy attachment and detachment of the air cap sheet. An aluminum insulating rod, prepared by insulating treatment, was attached to the lower part of the window-mounted air cap roller module to allow an indoor occupant to easily adjust the air cap sheet. The insulating rod
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insulating rod was designed for insulation by using an extruded polystyrene (XPS) insulation board insulating rod was designed for window-mounted insulation by by using usingair ancap extruded polystyrene (XPS) insulation insulation board insulating was designed for an extruded polystyrene (XPS) board attached torod thefor lower part of the roller module. Additionally, insulation was designed insulation by insulation using an extruded polystyrene (XPS) insulation boardanattached to attached to the lower part of the window-mounted air cap roller module. Additionally, an insulation attached topart the of lower of cap roller Additionally, module. Additionally, an insulation bar was inserted between thethe airwindow-mounted cap sheet theair glass surface of the window to resolve the was gap the lower the part window-mounted air and cap roller module. an insulation bar bar was wasby inserted between the the air air capcap sheet and the glass glass frame. surfaceThe of the the windowinsulation to resolve resolve bar the was gap bar inserted between air cap and the of the gap caused the attachment ofsheet the the surface window aluminum inserted between the air cap andsheet thetoglass ofsurface the window towindow resolve to the gap caused by caused by the attachment of the air cap to the window frame. The aluminum insulation bar was caused bybythe attachment of to thethe air cap to the window frame.into Theitinsulation aluminum insulation bar was prepared inserting polystyrene insulation for insulation and air-tightness. the attachment of the an airextruded cap window frame. The board aluminum bar was prepared by preparedwere by inserting inserting anboth extruded polystyrene insulation board into it for for insulationattachment and air-tightness. air-tightness. prepared by an extruded insulation board into it insulation and Springs placed at ends polystyrene of the insulation bar solid and convenient to the inserting an extruded polystyrene insulation board intofor it for insulation and air-tightness. Springs Springs were placed at both ends of the insulation bar for solid and convenient attachment towas the Springs were placed at both ends of the insulation bar for solid and convenient attachment inside of the window frame. A test bed of the proposed window-mounted air cap roller module were placed at both ends of the insulation bar for solid and convenient attachment to the inside to of the the inside of the window frame. A test bed of the proposed window-mounted air cap roller module was inside of frame. the the window test bed of(shown the proposed window-mounted cap roller installed for performance evaluation in Figure 4). air cap rollerair window A testframe. bed of A the proposed window-mounted module was module installedwas for installed for for the the performance performance evaluation evaluation (shown (shown in in Figure Figure 4). 4). installed the performance evaluation (shown in Figure 4).
Figure 1. Control of the coverage area by the window-mounted air cap roller module. Figure 1. 1. Control Control of of the the coverage coverage area area by by the the window-mounted window-mounted air air cap cap roller roller module. module. Figure
Figure 2. Control of the coverage area by the window-mounted air cap roller module (air cap sheet Figure 2. Control of the coverage area by the window-mounted air cap roller module (air cap sheet rolling). Figure 2. Control of the coverage areaarea by the air cap module (air cap rolling). Figure 2. Control of the coverage by window-mounted the window-mounted airroller cap roller module (airsheet cap sheet rolling). rolling).
Figure 3. 3. Configuration Configuration and function of the insulating insulating bar bar included included in the window-mounted window-mounted air cap Figure and function of the in the air cap Figuremodule. 3. Configuration and function of the insulating bar included in the window-mounted air cap roller Figuremodule. 3. Configuration and function of the insulating bar included in the window-mounted air cap roller roller module. roller module.
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Figure 4. Process of installing the window-mounted air cap roller module.
Figure 4. Process of installing the window-mounted air cap roller module. 2.2. Environment for Performance Evaluation
2.2. Environment for Performance Evaluation
The developed full-scale test bed for performance evaluation of the window-mounted air cap
The full-scale test 5bed performance evaluation of the rollerdeveloped module is detailed in Table andfor illustrated in Figure 5. The test bed waswindow-mounted 4.9 m wide, 2.5 m air cap roller module detailed in Table 5 andthe illustrated in Figure 5. was The2.2 test 4.9high, m wide, high, and 6.6 m is long. The window to which air caps were attached m bed wide,was 1.8 m and included transparent double glazing. To form an external environment for the performance 2.5 m high, and 6.6 m long. The window to which the air caps were attached was 2.2 m wide, an included artificial climate chamberdouble was installed outside window to controlenvironment the temperature. 1.8 mevaluation, high, and transparent glazing. To the form an external for the The external temperatures for the performance evaluation were determined to be −11.3 °C and 36.5 performance evaluation, an artificial climate chamber was installed outside the window to °C control for winter and summer, respectively [52]. The artificial climate chamber included an artificial solar the temperature. The external temperatures for the performance evaluation were determined to radiation apparatus to control the light intensity, height, and angle of the artificial light source to be −11.3 ◦ C and 36.5 ◦ C for winter and summer, respectively [52]. The artificial climate chamber form various external environmental conditions. Because the artificial solar light radiation apparatus included an artificial solar light radiation apparatus to control the light intensity, height, and angle of the employed an artificial source, the environmental conditions created for the performance artificial light source to form various external environmental conditions. Because the artificial evaluation were different from the actual conditions. However, the artificial light source satisfied the solar light Grade radiation apparatus employed an artificial light source, the environmental conditions created A measurement homogeneity standards, according to the ASTM E927-85 international standard. This ensured that uniform external environmental conditions were maintained for the performance evaluation were different from the actual conditions. However, between the artificial performance Due to the characteristics of the artificial according solar light radiation light the source satisfiedevaluation the Gradecases. A measurement homogeneity standards, to the ASTM apparatus used in this study, the performance evaluation was performed only with the conditions windows in were E927-85 international standard. This ensured that uniform external environmental question facing south. maintained between the performance evaluation cases. Due to the characteristics of the artificial solar Temperature and illumination sensors were installed as shown in Figure 6 to collect indoor light radiation apparatus used in this study, the performance evaluation was performed only with the environmental information. A temperature sensor was installed at the center of the indoor space, windows in question facing south. whereas four illumination sensors were installed at positions 2.2 and 4.4 m away from the window Temperature and installed as shown Figure 6 to collect indoor at a height of 0.75 m,illumination in accordance sensors with theirwere optimal measuring distancein [53]. environmental information. A temperature sensor was installed at the center of the indoor space, Table 5. Overview of test bed. whereas four illumination sensors were installed at positions 2.2 and 4.4 m away from the window at a height of 0.75 m, in accordance with their optimal measuring distance [53]. As shown in Table 6, to undertake the Room performance evaluation in this study, air conditioning and size, Material lighting appliances and automated Size:were installed 4.9in m the (W) ×test 6.6 mbed, (D) × 2.5 m (ceiling height) control of the air conditioner and Reflectability: Ceiling (86%), floor (25%)employed in this study allowed home lighting device was also established. The wall air (46%), conditioner panel (thickness: 0.1 m) and heating was 11,000 and 13,200 W, network-based Material: control, and the Insulation rated power for cooling respectively. On/off control of the air conditioner to maintain the appropriate indoor temperature was Window size, Material Size: 1.9 m (W) ×with 1.7 m the (H) indoor temperature sensor. In the off mode, the air performed automatically in coordination Type: at minimumDouble glazed 24 mm (6CL + 12A +or 6CL) conditioner operated power without cooling heating the indoor space but was never 2K (summer), 2.69 W/m2K (winter) Thermal transmittance: 2.83 W/m entirely turned off. For example, cooling of the indoor space was performed in summer when the Transmissivity: 80% 26 ◦ C; however, when the indoor temperature was below 26 ◦ C, indoor temperature was higher than Artificialpower solar Light Radiation Apparatus the air conditioner operated at minimum with only the fan running and did not perform cooling Precision of solar light radiation: Grade A (according to ASTM E927-85) duty. Heating of the indoor space was performed in winter when the indoor temperature was lower Range of illumination: 0–80,000 lx than 20 ◦ C; however, when the indoor temperature was below 20 ◦ C, heating was not performed, and Directions: South aspect the air conditioner continued to operate at minimum power. An LED lighting device allowed control in Sensor eight levels of illumination. The position ofTemperature the lighting device was determined based on a four-point Sensing element: silicon photo sensor, with filter method recommended by the Illuminating Engineering Society [49]. Illumination sensors 1, 2, 3, and 4 Detection range: lx were connected to lights 1, 2, 3, and0–200,000 4, respectively, to control the indoor illumination values. When the Precision: measured illumination value was±3% below 500 lx, the lights were automatically brightened, beginning with the illumination sensor that showed the lowest illumination value, until an illumination of 500 lx was reached. For example, when an indoor illumination value of 400 lx was measured by illumination sensor 1, the light connected to that sensor was brightened from level 1 up to level 8, until the value
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reached 500 lx or higher. If the minimum indoor illumination value did not reach 500 lx even after the brightness control of light No. 1 to level 8, the brightness level of light No. 3, which was the light nearest to the illumination sensor, showed the lowest illumination value, and was sequentially elevated from level 1 to level 8 until the minimum indoor illumination value measured by the illumination sensors exceeded 500 lx. This brightness control was repeated until the minimum indoor illumination value exceeded 500 lx. Table 5. Overview of test bed. Room size, Material 4.9 m (W) × 6.6 m (D) × 2.5 m (ceiling height) Ceiling (86%), wall (46%), floor (25%) Insulation panel (thickness: 0.1 m)
Size: Reflectability: Material:
Window size, Material 1.9 m (W) × 1.7 m (H) Double glazed 24 mm (6CL + 12A + 6CL) 2.83 W/m2 K (summer), 2.69 W/m2 K (winter) 80%
Size: Type: Thermal transmittance: Transmissivity:
Artificial solar Light Radiation Apparatus Precision of solar light radiation: Range of illumination: Directions:
Grade A (according to ASTM E927-85) 0–80,000 lx South aspect Temperature Sensor
Sensing element: Detection range: Precision:
silicon photo sensor, with filter 0–200,000 lx ±3% Illuminance Sensor
Sensing element: Detection range: Precision:
NTC 10 KΩ; AN type −40 ◦ C to +90 ◦ C ±0.3 ◦ C Energy Monitoring System
Measurement capacity: Measurement items: Error rate:
Single phase (220 V, 1–50 A) Power/voltage/current, real-time, and accumulated amount within 2.0%
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Table 6. Specifications of the lighting devices and air conditioner. Illuminance Sensor
Device Sensing element:
NTC 10 KΩ; AN type
Specifications
Type: 8-level dimming (LED type) Detection range: −40 °C to +90 °C Electricity consumption according to the level of dimming lighting control: lv 1 (12 W), lv 2 Lighting Precision: ±0.3 °C (18 W), lv 3 (22 W), lv 4 (28 W), lv 5 (34 W), lv 6 (39 W), lv 7 (43 W), lv 8 (51 W) Energy Monitoring System heating temperature: 35 ◦ C Measurement capacity: Measurement items: Air conditioner Error rate:
Single phase (220 V,Model: 1–50 A) AP-SM302 (EHP)
Heating/cooling capacity: W/11,000 W Power/voltage/current, real-time, and 13,200 accumulated amount
Heating/cooling energy consumption: 3.90 kW/3.90 kW COP: heating: 3.38/cooling: 2.82
within 2.0%
Figure 5. 5. Overview andmeasurement measurement apparatus. Figure Overviewof oftest test bed bed and apparatus.
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Figure 5. Overview of test bed and measurement apparatus.
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Figure Figure6.6. Floor Floor plan planand andsectional sectionalview viewof oftest testbed. bed.
2.3. Method of Performance As shown in Table 6,Evaluation to undertake the performance evaluation in this study, air conditioning and In lighting appliances were installed in the test bed, and control of the air conditioner this section, the performance evaluation method for automated the proposed window-mounted air cap and lighting device was also established. The air conditioner employed in this study allowed roller is detailed. As shown in Table 7, the evaluation was conducted for six cases: (Case 1) airhome caps network-based control, and surface; the rated power cooling andfrom heating wasof11,000 13,200 W, attached to the entire window (Case 2) airfor caps attached a height 1.2 m, and corresponding respectively. of the airtop conditioner to maintain appropriate indoor to eye level at On/off a sittingcontrol position, to the of the window; (Case the 3) air caps attached fromtemperature a height of was performed automatically in coordination with the indoor temperature sensor. In the 1.5 m, corresponding to eye level at a standing position, to the top of the window; (Case 4)off airmode, caps attached from a height of 1.8 m from the floor to the top of the window; (Case 5) air caps attached from a height of 2.1 m from the floor to the top of the window; and (Case 6) no air caps attached. The settings for Cases 4 and 5 were established by adjusting the settings of Cases 1, 2 and 3, which considered the eye level of building residents. In other words, the heights of the air caps in Cases 2, 3, 4, and 5 were adjusted in 0.3-m increments to make it possible to undertake performance evaluations according to the area of air cap coverage. Because the lighting devices and air conditioner were automatically switched on and off to maintain the appropriate lighting and temperature levels, the power consumed by these devices was used as a performance indicator for each case. The thermal properties of the air cap sheets were dependent on the position of the internal air layers, thus limiting the calculation of thermal conductivity, heat transmission coefficient, and thermal resistance. Furthermore, the power consumed by the lighting devices was calculated by setting the minimum illumination measured by the indoor illumination sensors to 500 lx. In addition, to evaluate the reduction of the energy consumption for cooling and heating in each case, the temperature sensor located at the center of the indoor space was connected to the air conditioner, which was automatically controlled to maintain the predetermined appropriate indoor temperature. In this study, the power consumed by the automatically controlled air conditioner was used as a quantitative performance evaluation indicator. However, the cooling and heating energy consumption was measured while performing dimming control of the lights to satisfy the appropriate indoor illumination standard.
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located at the of the connected to the air which located at the the of the the spacespace was was connected to the the which was was located at center the center center of indoor the indoor indoor space was connected to air the conditioner, air conditioner, conditioner, which was located at of space was connected to which was located at center the center of indoor the indoor space was connected to air the conditioner, air conditioner, which was automatically controlled to maintain the predetermined appropriate indoor temperature. In this automatically controlled to maintain the predetermined appropriate indoor temperature. In this automatically controlled to maintain the predetermined appropriate indoor temperature. In this automatically controlled to maintain the predetermined appropriate indoor temperature. In this automatically controlled to maintain the predetermined appropriate indoor temperature. In this Energies 2018, 11, 1909 8 of 14 study, the power consumed by the automatically controlled air conditioner was used as a quantitative study, the power consumed by the automatically controlled air conditioner was used as a quantitative study, the power consumed by the automatically controlled air conditioner was used as a quantitative study, the power consumed by the controlled air conditioner was used as a quantitative study, the power consumed byautomatically the automatically controlled air conditioner was used as a quantitative performance evaluation indicator. However, the cooling and heating energy consumption was performance evaluation indicator. However, the cooling cooling and heating heating energy consumption was was performance evaluation indicator. However, the cooling and heating energy consumption performance evaluation indicator. However, the and energy consumption was performance evaluation indicator. However, the cooling and heating energy consumption was measured while performing dimming control of the lights to satisfy the appropriate indoor measured while performing dimming control of the lights to satisfy the appropriate indoor measured while performing dimming control of the lights to satisfy the appropriate indoor measured whilewhile performing dimming control of the lights to satisfy the appropriate indoor measured performing dimming control of the lights to satisfy the appropriate indoor The performance evaluation was limited to summer and winter, when air conditioners and illumination standard. illumination standard. illumination standard. illumination standard. illumination standard. heatingThe are performance most used, between 10 was a.m. limited and limited 3 p.m. The selected external illumination and temperature The performance performance evaluation was limited to summer summer and winter, when air conditioners conditioners and evaluation to summer summer and winter, winter, when air conditioners conditioners and and The evaluation was to and winter, when air The performance evaluation was limited to and when air and The performance evaluation was limited to summer and winter, when air conditioners and heating are most most used, between 10 a.m. a.m. and 3 8p.m. p.m. The selected external illumination and conditions for summer and winter are shown in Table [52] and were simulated by varying the input heating are most used, between 10 a.m. and 3 p.m. The selected external illumination and heating are used, between 10 and 3 The selected external illumination and heating are most used,used, between 10 a.m. and and 3 p.m. The The selected external illumination and and heating are most between 10 a.m. 3 p.m. selected external illumination temperature conditions for summer summer and winter winter are shown shown in Table Table 8 and [52] were and were were simulated by temperature conditions for summer and winter are shown in Table 8 [52] simulated by temperature conditions for and are in 8 [52] and simulated by solar radiation and artificial lighting. temperature conditions for summer and winter are shown in Table 8 [52]8 and simulated by by temperature conditions for summer and winter are shown in Table [52] were and were simulated varying the input input solar radiation and artificial artificial lighting. varying the input solar radiation and artificial lighting. varying the solar radiation and lighting. varying the input solarsolar radiation and artificial lighting. varying the input radiation and artificial lighting. Table 7. Cases for the performance evaluation.
Case Case Case Case Case Case Case
7. the evaluation. TableTable 7. Cases Cases for the thefor performance evaluation. Table 7. Cases Cases for the performance performance evaluation. Table 7. for performance evaluation. TableTable 7. Cases for the performance evaluation. 7. Cases for the performance evaluation. Ratio of Air Cap Ratio of Air Cap Ratio of of Airof Cap Ratio Air Cap Ratio Cap Ratio of Air Air Cap Ratio of Air Cap Coverage Area toto Entire Coverage Area to Entire Case Coverage Area to Entire Case Case Coverage Area Entire Case Coverage Area to Entire Case Coverage Area to Entire Case Case Coverage Area to Entire Window Area (%) Window Area Window Area (%) Window Area (%) (%) Window Area Window Area (%) (%) Window Area (%)
Ratio ofAir Air Cap Ratio Cap Ratio of of Airof Cap Ratio of Air Cap Ratio Cap Ratio of Air Airof Cap Ratio Airto Cap Coverage Area to Entire Coverage Area Entire Coverage Area to Entire Coverage Area to Entire Coverage Area Entire Coverage Area to to Entire Coverage Area to (%) Entire Window Area (%) Window Area Window Area (%) (%) Window Area (%) Window Area Window Area (%) Window Area (%)
100100100 100 100 100 100
27.5 27.5 27.5 27.5 27.5 27.5 27.5
(Case 1) Aircovering caps covering covering (Case 1) Air 1) caps (Case Air caps
(Case 4) Air caps attached from (Case 4) Air caps attached (Case 4) 4) Air 4) caps attached from (Case Air caps attached from (Case caps attached from (Case (Case 4)a Air Air 4) caps attached fromtop Air capsmattached from of 1.8 of height of a1.8 1.8 m to the topthe of top from height of 1.8 m to the a height height of to 1.8the m to to the of aaa height of m top of height of 1.8 m the topthe of top of a height of 1.8 m to theto window the window the window top of the window the the window window the window
(Case 1) Air caps covering (Case 1) Air caps covering (Case 1) Air caps covering the (Case 1) Air caps covering the window the entire entire window surfacesurface the entire entire window surface the window surface the entire window surface entire window surface the entire window surface
73 73 73 73 73 73 73 (Case 2) Air caps attached
46 46 46 46 46 4646 (Case Air caps (Case 3) 3) Air 3) caps attached (Case 3) Airattached caps attached attached (Case Air caps
9.1 9.1 9.1 9.1
000
00 00
(Case Air caps attached from (Case 5) 5) Air 5) caps attached from (Case 5) Air caps attached from (Case Air caps attached from 5) Air caps attached (Case (Case 5)(Case caps from 5) Air caps from a Air height ofattached 2.1 mattached to the top of a height of 2.1 m to the top of a height of 2.1 m to the top of aa height of m to the top of from height of 2.1 m to the height of a2.1 2.1 m to the top of a height of 2.1 m to the top of the window the window thethe window the window top of window the window the window
(Case2) 2) Air caps caps (Case 2) Airattached caps attached (Case attached (Case 2) Air caps (Casefrom 2)Air Air caps attached (Case 2) Airattached caps height of to 1.2attached m to to the the fromaaafrom height of 1.2 1.2 m the aa height of 1.2 m from height of 1.2m mto tothe theto the from height from afrom height of 1.2 m to the a height of 1.2 m top of the window topof of the the of window top the window top window top of the window top of top the of window the window
(Case3) 3)Air Air caps (Case 3) Airattached caps attached (Case caps aa height of 1.5 m from aafrom height of 1.5 1.5attached m to the from height of to 1.5the m to to the the from height of m fromaafrom height of 1.5 to a height of 1.5 m from height of 1.5 m tothe theto the top of them window top of the window top of the window top of the window top of the window top of the window top of the window
9.1 9.1 9.1
(Case 6) air caps (Case 6) 6) No air air caps (Case 6) No No airattached caps attached attached (Case caps (Case (Case 6) No No 6) airNo caps attached airattached caps attached
(Case 6) No air caps attached
Table 8. External External illumination, solar radiation, radiation, and outdoor outdoor temperature conditions intime eachzone. time zone. zone. TableTable 8. External External illumination, solar radiation, radiation, and outdoor outdoor temperature conditions in each each 8. illumination, solar and temperature conditions in each time Table 8. illumination, solar and temperature conditions in TableTable 8. External illumination, solar radiation, and outdoor temperature conditions in each time zone. 8. External illumination, solar radiation, and outdoor temperature conditions intime eachzone. time zone.
Table 8. External illumination, solar radiation, and outdoor temperature conditions in each time zone.
TimeTime Zone Zone Time Zone Time Zone TimeTime Zone Zone 10:00–12:00 12:00–13:00 10:00–12:00 12:00–13:00 10:00–12:00 12:00–13:00 Time Zone 10:00–12:00 12:00–13:00 10:00–12:00 12:00–13:00 10:00–12:00 12:00–13:00 Season External illumination 70,000(±100) lx 80,000(±100) lx External illumination lx 80,000(±100) lx External illumination 70,000(±100) 70,000(±100) lx 80,000(±100) lx 10:00–12:00 12:00–13:00 External illumination lx 80,000(±100) lx External illumination 70,000(±100) lx 80,000(±100) lx External illumination 70,000(±100) 70,000(±100) lx 80,000(±100) lx 2 2 2 2 22 Solar radiation 429(±2) W/m 503(±2) W/m Solar radiation 429(±2) W/m 503(±2) W/m Solar radiation 429(±2) W/m 503(±2) W/m 2 2 2 2 100) radiation 429(±2) W/m W/m External illumination 70,000( ±2100) lx503(±2) 80,000( Solar Solar radiation 429(±2) W/m 503(±2) W/m± Summer radiation 429(±2) W/m 503(±2) W/m2 lx Summer Summer Solar Summer Summer Altitude 76.5° Summer Altitude 76.5° Altitude 76.5° Solar radiation 429(±2) W/m2 503(± 2) W/m2 Altitude 76.5° Altitude 76.5° Altitude 76.5° Summer External ◦ temperature 34(±1) Altitude 76.5°C External temperature 34(±1)34(±1) °C External temperature °C External temperature 34(±1) °C External temperature 34(±1)34(±1) °C °C External temperature ◦ External temperature 34( ± 1) External illumination 20,000(±100) 20,000(±100) lx 30,000(±100) lx External illumination lx 30,000(±100) lx Clx External illumination 20,000(±100) lx 30,000(±100) External illumination lx 30,000(±100) lx External illumination 20,000(±100) lx 30,000(±100) lx External illumination 20,000(±100) 20,000(±100) lx 30,000(±100) lx 2 2 2 2 2 Solar radiation 283(±2) W/m 340(±2) W/m External illumination 20,000( ± 100) lx 30,000( ± 100) Solar Solar radiation 283(±2) W/m22W/m2 340(±2) W/m22W/m22 lx radiation 283(±2) 340(±2) radiation 283(±2) W/m 340(±2) W/m Solar Solar radiation 283(±2) W/m W/m W/m W/m 2 Winter Solar radiation 283(±2) 340(±2) 2340(±2) Winter Winter Solar radiation Winter 283( ± 2) W/m 340( ± 2) W/m Winter Altitude 29.5° Winter Altitude 29.5° 29.5° Altitude Winter Altitude 29.5° Altitude 29.5° 29.5° Altitude Altitude 29.5◦ External temperature −10(±1) External temperature −10(±1) °C °C External temperature −10(±1) °C External temperature −10(±1) °C External temperature −10(±1) °C±1) External temperature − 10( External temperature −10(±1) °C◦ C Season Season Season Season Season Season
12:00–14:00 12:00–14:00 12:00–14:00 12:00–14:00 12:00–14:00 12:00–14:00 70,000(±100) lx 70,000(±100) lx 70,000(±100) lx 12:00–14:00 70,000(±100) lx 70,000(±100) lx 70,000(±100) lx 2 22 429(±2) W/m 429(±2) W/m 429(±2) W/m 2 2 lx 2 429(±2) W/m 70,000( ± 100) 429(±2) W/m 429(±2) W/m
429(±2) W/m2
20,000(±100) lx 20,000(±100) lx 20,000(±100) lx 20,000(±100) lx 20,000(±100) lx 20,000(±100) lx 2 2 283(±2) W/m 20,000( ± 100) lx 283(±2) W/m22W/m22 283(±2) 283(±2) W/m 283(±2) W/m W/m 283(±2) 2
283(±2) W/m
3. Results and Discussion of Performance Evaluation In contrast to Case 6, which did not have air cap attachments, Cases 1 through 5, all of which had air cap attachments, presented lower average indoor illumination. This was due to the reduced amount of natural light introduced into the indoor space by the air caps attached to the windows. In addition, increases in the air-cap coverage area reduced the amount of natural light being introduced indoors, resulting in lower average indoor illumination. It was also possible to confirm this through the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated that increases in the air cap coverage area resulted in increases in energy consumption for indoor lighting
Energies 2018, 11, x FOR PEER REVIEW Energies 2018, 11, x FOR 2018, PEER 11, REVIEW xx FOR PEER REVIEW Energies 2018, 11, xx FOR PEER REVIEW Energies 2018, 11,Energies FOR PEER REVIEW Energies 2018, 11, FOR PEER REVIEW Energies 2018, 11,REVIEW FOR PEER REVIEW Energies 2018, 11, x PEER REVIEW Energies 2018, 11, x FOR PEER REVIEW Energies 2018, 11, xx FOR PEER Energies 2018, 11, x FOR FOR PEER REVIEW Energies 2018, 11, x FOR PEER REVIEW
9 15 of 15 15 99 of of9 15 of 9 of 9 15 of 15
9 15 of 15 99 of of 15 of 15 15 99 15 of 9 of
3. Results and Discussion Performance Evaluation 3. Results and 3. Results Discussion and of Performance of Performance Evaluation 3. Results and of Performance Evaluation 3. 3. Results and Discussion ofDiscussion Performance Evaluation 3. Results and Discussion of Performance EvaluationEvaluation 3.Discussion Results and Discussion of of Performance Evaluation 3. Results and Discussion of Performance Evaluation 3. Results and Discussion of Performance Evaluation Results and of Performance Evaluation 3.Discussion Results and Discussion of Performance Evaluation 3. Results and Discussion of Performance Evaluation In contrast to Case 6, which did not have cap attachments, Cases 1 5, which In contrast In to contrast Case 6, which to Case did 6, not which have did air not cap have attachments, air cap attachments, Cases 1 through Cases 5, 11 through all of which 5, of which In contrast to Case 6, which did not have air cap attachments, Cases 11 through 5, all which InIn contrast toIn Case 6, 6, which did not have airair cap attachments, Cases through 5, 5, all ofthrough which In contrast to Case 6, which did not have air cap attachments, Cases through 5, all of which In contrast to to Case 6, which did not have airair cap attachments, Cases through 5, all allall of of which In contrast to Case 6, which did not have air cap attachments, Cases 1of through 5, all of which contrast to Case 6, which did not have air cap attachments, Cases 1 through 5, all of which contrast to Case which did not have cap attachments, Cases 11 through all of which In contrast Case 6, which did not have air cap attachments, Cases 1 through 5, all of which In contrast to Case 6, which did not have air cap attachments, Cases 1 through 5, all of which had air cap attachments, presented lower average indoor illumination. This was due to the reduced had air cap had attachments, air cap attachments, presented lower presented average lower indoor average illumination. indoor illumination. This was due This to was the reduced due to the reduced had air cap attachments, presented lower average indoor illumination. This was due to the reduced had air cap attachments, presented lower average indoor illumination. This was due to the reduced had air cap attachments, presented lower average indoor illumination. This was due to the reduced had air cap attachments, presented lower average indoor illumination. This was due to the reduced had air cap attachments, presented lower average indoor illumination. This was due to the reduced had airair capcap attachments, presented lower average indoor illumination. This was due to to thethe reduced had cap attachments, presented lower average indoor illumination. This was due to the reduced had attachments, presented lower average indoor illumination. was due reduced had airair cap attachments, presented lower average indoor illumination. This was due toThis the reduced Energies 2018,of 1909 9 of 14 amount of natural light introduced into indoor space by the attached windows. amount of natural amount light of natural introduced light introduced into the indoor into space the indoor by the space air caps by the attached air caps to attached the windows. to the In windows. In amount natural light into the indoor space by the air caps to the windows. In amount of11, natural light introduced into the indoor space byby the air caps attached tocaps the windows. Inthe amount of natural light introduced into the indoor space by the air caps attached to the windows. In amount of introduced natural light introduced into thethe indoor space byattached the airair caps attached to to the windows. In In amount of natural light introduced into the indoor space by the air caps attached to the windows. In amount of natural light introduced into the indoor space by the air caps attached to the windows. In amount of natural light introduced into the indoor space the air caps attached to the windows. In amount of natural light introduced into the indoor space by the air caps attached to the windows. In amount of natural light introduced into the indoor space by the air caps attached to the windows. In addition, increases in the air-cap coverage area reduced the amount of natural light being introduced addition, increases addition, in increases the air-cap in coverage the air-cap area coverage reduced area the reduced amount the of natural amount light of natural being introduced light being introduced addition, increases in the air-cap coverage area reduced the amount of natural light being introduced addition, increases inin the air-cap coverage area reduced the amount ofthe natural light being introduced addition, increases in the air-cap coverage area reduced the amount of natural light being introduced addition, increases in thethe air-cap coverage area reduced the amount ofbeing natural light being introduced addition, increases in the air-cap coverage area reduced the amount of natural light being introduced addition, increases in the air-cap coverage area reduced amount of natural light being introduced addition, increases the air-cap coverage area reduced the amount of natural light being introduced addition, increases in air-cap coverage area reduced the amount of natural light being introduced addition, increases in the air-cap coverage area reduced the amount of natural light introduced indoors, resulting in lower average indoor illumination. It was was also possible to confirm this through indoors, resulting indoors, in resulting lower average in lower indoor average illumination. indoor illumination. It was also It possible also to possible confirm this to confirm through this through indoors, resulting in lower average indoor illumination. It was also possible to confirm this indoors, resulting inin lower average indoor illumination. It It was also possible toto confirm this through indoors, resulting in lower average indoor illumination. It was also possible to confirm this through indoors, resulting in in lower average indoor illumination. It was was also possible tothrough confirm this through indoors, resulting lower average indoor illumination. It also possible to confirm this through indoors, resulting in lower average indoor illumination. It was also possible to confirm this through indoors, resulting lower average indoor illumination. was also possible confirm this through indoors, resulting in lower average indoor illumination. It was also possible to confirm this through indoors, resulting in lower average indoor illumination. It was also possible to confirm this through the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated the indoor images the indoor of each images case, of as each presented case, as in presented Table 9. As in Table shown 9. in As Table shown 10, in the Table results 10, indicated the results indicated the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated purposes. For example, Cases 1 through 5 presented an increase in energy consumption between the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated the indoor images of each case, as presented in Table 9. As shown in Table 10, the results indicated indoor images of each case, presented Table shown results indicated theof indoor images of each case, as presented in Table 9. Table As shown in Tableindicated 10, the results indicated thethe indoor images each case, asas presented inin Table 9. 9. AsAs shown inin Table 10,10, thethe results increases in the cap coverage area resulted in increases energy consumption indoor that increases that in increases the air cap in the coverage air cap area coverage resulted area in resulted increases in in increases energy consumption in energy consumption for indoor for indoor that increases in the air cap area resulted in increases in energy consumption for indoor that increases inthat the airair cap coverage area resulted in increases in energy consumption for indoor that increases in the air cap coverage area resulted in increases in energy consumption for indoor52.1% that increases incoverage the airair cap coverage area resulted inin increases in in energy consumption forfor indoor that increases in the air cap coverage area resulted in increases in energy consumption for indoor that increases in the air cap coverage area resulted in increases in energy consumption for indoor that increases in the cap coverage area resulted in increases energy consumption for indoor that increases in the air cap coverage area resulted in increases in energy consumption for indoor that increases in the air cap coverage area resulted in increases in energy consumption for indoor 4.3% and 17.8% during the summer season and an increase between 12.3% and during the lighting purposes. For example, Cases 1 through through 5increase presented an increase in energy consumption lighting purposes. lighting For purposes. example, For Cases example, 11 through Cases 5511 presented through 55 an presented increase in increase energy consumption in energy consumption lighting purposes. For example, Cases 11 through 55 presented an in energy consumption lighting purposes. For example, Cases an increase inan energy consumption lighting purposes. For example, Cases through presented an increase in energy consumption lighting purposes. For example, Cases through presented an increase in in energy consumption lighting purposes. For example, Cases 1 5 presented an increase energy consumption lighting purposes. For example, Cases 1 presented through 5 an presented an increase in energy consumption lighting purposes. For example, Cases 1through through 5presented increase in energy consumption lighting purposes. For example, Cases 1 through 5increase presented an increase in energy consumption lighting purposes. For example, Cases 1 6. through 5 presented an in energy consumption winter season compared with Case To summarize the above, an increase in the air cap coverage between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% between and 17.8% 4.3% during and 17.8% the summer during the season summer and an increase and an between increase 12.3% between and 52.1% 12.3% during and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and anseason increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during between 4.3% and 17.8% during the summer season and an increase between 12.3% and 52.1% during the winter season compared with Case 6.in To summarize the above, an increase in the air cap coverage the winter season the winter compared season with compared Case 6. with To summarize Case 6. To summarize the above, an the increase above, an in the increase air cap in coverage the air cap coverage winter season compared with Case 6. To summarize the above, an increase in the air cap coverage areathe reduced the natural light volumes, which turn increased the energy consumption required to the winter season compared with Case 6. To summarize the above, an increase in the air cap coverage the winter season compared with Case 6. To summarize the above, an increase in the air cap coverage the winter season compared with Case 6. To summarize the above, an increase in the air cap coverage the winter season compared with Case 6. To summarize the above, an increase in the air cap coverage thethe winter season compared with Case 6. To summarize the above, increase incoverage thethe airair capcap coverage winter season compared with Case To summarize the above, increase in the air cap winter season compared with Case 6.the To summarize the above, an increase in coverage thethe winter season compared with Case 6. 6. To summarize above, anan increase inan the air cap coverage area reduced the natural light volumes, which in turn increased the energy consumption required to area reduced area the reduced natural the light natural volumes, light which volumes, in turn which increased in turn the increased energy consumption the energy consumption required to required to area reduced the natural light volumes, which in turn increased the energy consumption required to area reduced the natural light volumes, which in turn increased the energy consumption required to area reduced the natural light volumes, which in turn increased the energy consumption required to area reduced the natural light volumes, which in turn increased the energy consumption required to area reduced the natural light volumes, which in turn increased the energy consumption required to maintain the appropriate indoor illumination levels. In regards to Cases 1 through 5, which had air area reduced the natural light volumes, which in in turn increased thethe energy consumption to to area reduced natural light volumes, which turn increased the energy consumption required area reduced the natural light volumes, which turn increased energy consumption required area reduced thethe natural light volumes, which inin turn increased the energy consumption required to to required maintain appropriate indoor illumination levels. In regards Cases 1 5, had maintain the maintain appropriate the appropriate indoor illumination indoor illumination levels. In regards levels. to In Cases regards 1 through to Cases 5, 11 which through had 5, air had air maintain the appropriate indoor illumination levels. In regards to Cases 11 through 5, which had air maintain the appropriate indoor illumination levels. InIn regards toto Cases through 5, 5, which had airwhich maintain the appropriate indoor illumination levels. In regards to Cases through 5, which had airwhich maintain thethe appropriate indoor illumination levels. In regards to to Cases through 5, which had airair maintain the appropriate indoor illumination levels. In regards to Cases 1 through through 5, which had air maintain the appropriate indoor illumination levels. In regards to Cases 1 which through 5, which had air maintain the appropriate indoor illumination levels. regards Cases 11 through had air maintain the appropriate indoor illumination levels. In regards to Cases 1 through 5, which had air the appropriate indoor illumination levels. In regards to Cases 15.6% through 5, which had air cap maintain attachments, an increase in energy consumption between and 25.7% during the summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer and cap attachments, cap attachments, an increase in increase energy consumption in energy consumption between 5.6% between and 25.7% 5.6% and during 25.7% the during summer the summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer cap attachments, anan increase inan energy consumption between 5.6% and 25.7% during the summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer cap attachments, an increase in in energy consumption between 5.6% and 25.7% during thethe summer cap attachments, an increase energy consumption between 5.6% and 25.7% during summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer cap attachments, increase in energy consumption between 5.6% and 25.7% during the summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer cap attachments, an increase in energy consumption between 5.6% and 25.7% during the summer winter seasons compared with Case 6 was needed to reach the appropriate 500 lx indoor illumination and winter seasons compared with Case 6 was needed to reach appropriate 500-lx indoor and winter and seasons winter compared seasons with compared Case 6was was Case needed 66 was to needed reach the to appropriate reach the appropriate 500-lx indoor 500-lx indoor and winter compared with Case 66 with needed to reach the appropriate 500-lx indoor and winter seasons compared with Case was needed reach the appropriate 500-lx indoor and winterseasons seasons compared with Case was needed to reach the appropriate 500-lx indoor and winter seasons compared with Case was needed to reach thethe appropriate 500-lx indoor and winter seasons compared with Case 6 was needed to reach the appropriate 500-lx indoor and winter seasons compared Case 6 was needed to reach the appropriate 500-lx indoor and winter seasons compared with Case 66was was needed reach the appropriate 500-lx indoor and winter seasons compared with Case 6toto was needed to reach the appropriate 500-lx indoor and winter seasons compared with Case 6 with needed to reach the appropriate 500-lx indoor illumination level. In light of this, these cases were considered inappropriate to reduce the energy illumination illumination level. In light level. of this, In light these of cases this, these were cases considered were considered inappropriate inappropriate to reduce the to reduce energy the energy illumination level. In light of this, these cases were considered inappropriate to reduce the energy illumination level. InIn light oflevel. this, these cases were considered inappropriate to reduce the energy level. In light of this, these cases were considered inappropriate toinappropriate reduce the energy consumption for illumination level. In light of this, these cases were considered inappropriate to reduce the energy illumination level. In In light of this, these cases were considered inappropriate to reduce the energy illumination level. In light of this, these cases were considered inappropriate to reduce the energy illumination level. In light of this, these cases were considered to reduce the energy illumination level. light of this, these cases were considered inappropriate to reduce the energy illumination light of this, these cases were considered inappropriate to reduce the energy illumination level. In light of this, these cases were considered inappropriate to reduce the energy consumption for lighting purposes. consumption consumption for lighting for purposes. lighting purposes. consumption for lighting purposes. consumption forconsumption lighting purposes. consumption for lighting purposes. consumption for lighting purposes. for lighting purposes. consumption for lighting purposes. consumption for lighting purposes. consumption for lighting purposes. consumption for lighting purposes. lighting purposes. Table 9. Images Images ofand individual cases and sum ofconsumption electrical power consumption for each case. Table 9. Images Table of 9. individual Images of cases individual and sum cases of electrical and sum power of consumption power consumption for each case. each case. Table 9. Images of individual cases sum of electrical power for each case. Table 9. 9. Images ofTable individual cases and sum of of electrical power consumption for each case. Table 9. Images Images of individual cases and sum of electrical power consumption for each case.for Table 9. Images ofcases individual cases and sum of electrical electrical power consumption forfor each case. 9. of individual cases and sum of electrical power consumption each case. Table 9. Images of individual cases and sum of electrical power consumption for each case. Table of individual and sum electrical power consumption for each case. Table 9. Images ofand individual cases and sum ofconsumption electrical power consumption for each case. Table 9. Images of individual cases sum of electrical power for each case.
Table 9. Images of individual cases and sum of electrical power consumption for each case.
Indoor Images Each Case Indoor Images for Each Case Sum of Indoor Images Indoor for Each Images Case for Each Case Indoor Images Indoor for Each Images Case for Each Sum Case of Sum of Indoor Images for Each Case Indoor Images for Each Case Sum of Indoor Images for Each Case Indoor Images for Each Case Sum ofCase Indoor Images for Each Case Indoor Images for Each Case Sum of Indoor Images forfor Each Case Indoor Images forfor Each Case Sum of of Indoor Images for Each Case Indoor Images Each Sum Indoor Images for Each Case Indoor Images for Each Case Sum of Indoor Images for Each Case Indoor Images for Each Case Sum of Indoor Images for Each Case Indoor Images for Each Case Sum of Indoor Images for Each Case Indoor for Each Case Sum of Sum of Images Sum of Sum of Sum of Sum of Sum of Sum of Sum of Sum of Sum of Sum of Sum of Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Electrical Indoor Images for Each Case Indoor Images for Each Case Electrical Electrical Electrical Sum of Electrical Sum of Electrical Electrical Electrical Electrical Electrical Power Power Power Power Summer Winter Summer Winter Summer Summer Winter Winter Summer Summer Winter Winter Summer Winter Summer Winter Power Power Power Power Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Power Power Power Power Power Power Power Power Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter Summer Winter PowerCase Power Power Power Power Power Power Power Power Power Case Case Consumption Case Case Case Case Consumption Consumption Case Consumption Winter Summer Winter Summer (External (External (External (External (External (External (External (External (External (External (External (External (External (External (External (External Case Case Consumption Case Case Consumption Case Case Consumption Case Case Consumption (External (External (External (External (External (External Consumption (External (External Consumption (External (External (External (External (External (External (External (External Consumption Case Case Case (External Case Consumption Case (External Case (External Consumption Case Case Consumption Consumption Consumption (External (External (External (External (External (External (External (External (External (External (External (External Consumption by (External Consumption by Case Case Consumption Consumption Consumption Consumption (External (External (External (External Consumption Consumption Consumption Consumption Lighting by Lighting Lighting by Lighting Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: by Lighting by Lighting by byby Lighting by LightingDevices Illuminance: Illuminance: Illuminance: Illuminance: Illuminance:Illuminance: Illuminance:Illuminance: Illuminance:Illuminance: Illuminance:Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: by Lighting by Lighting by Lighting by Lighting Lighting Devices Lighting by Lighting by Lighting by Lighting by Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: Illuminance: by Lighting by Lighting by Lighting by Lighting Illuminance: Illuminance: Illuminance: Illuminance: by Lighting by Lighting by Lighting by30,000 Lighting Devices Devices Devices Devices 80,000 lx)lx) lx) 80,000 lx)lx) 30,000 lx) 80,000 lx) 80,000 30,000 lx) 30,000 lx) 80,000 lx) 80,000 30,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) Devices Devices Devices Devices 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx) 30,000 lx) (kWh) (kWh) Devices Devices Devices Devices Devices (kWh) Devices (kWh) Devices (kWh) (kWh) lx)lx) 30,000 lx) 80,000 lx)lx) lx)lx) 80,000 30,000 lx) Devices 80,000 30,000 lx) 30,000 80,000 lx)lx) 30,000 lx) 80,000 lx) 30,000 lx) 80,000 lx)lx) 80,000 30,000 80,000 lx)lx) 80,000 30,000 Devices (kWh) 30,000 lx) 30,000 80,000 lx) Devices (kWh) Devices (kWh) Devices (kWh) Devices (kWh) Devices (kWh) Devices (kWh) Devices (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) (kWh) 1 11 11 1 1
11 11 1 1
0.834 44 0.834 0.834 0.834 44 0.834 4 0.834 0.834 0.834 0.834 40.834 0.834 0.834 4 0.834
44 44 4 4
0.703 0.703 0.703 0.703 0.703 0.703
0.703 0.703 0.703 0.7030.703 0.703 0.703
2 2 2 22 22
22 22 2 2
0.798 5 0.798 0.798 55 0.798 0.798 0.798 0.798 0.798 5 0.798 50.798 0.798 0.798 55 0.798
55 55 5 5
0.657 0.657 0.657 0.657 0.657 0.657
0.6570.657 0.657 0.657 0.657 0.657 0.657
3 3 3 33 33
33 33 3 3
0.731 0.731 66 0.731 0.731 6 0.731 0.731 0.731 0.731 60.731 0.731 6 0.731 0.731 66 0.731
66 66 6 6
0.620 0.620 0.620 0.620 0.620 0.620
0.620 0.620 0.620 0.620 0.620 0.6200.620
Table 10. Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting Table 10. device Lighting control device and control power and consumption power consumption for maintaining for maintaining appropriate appropriate indoor indoor Table 10. Lighting device control and power consumption for maintaining indoor Table 10.10. Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting device control and power consumption forappropriate maintaining appropriate indoor Table 10. Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting device control and power consumption for maintaining appropriate indoor Table Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting device control and power consumption for maintaining appropriate indoor Table 10. Lighting device control and power consumption for maintaining appropriate indoor illumination. illumination.illumination. illumination.
illumination. illumination. illumination. illumination. illumination. illumination. illumination. The effects onillumination. the heating and cooling energy consumption of attaching the air cap roller module Summer Summer Summer are presented in Table 11. The greatestSummer reduction in the cooling and heating energy consumption Summer Summer Summer Summer Summer Summer Summer Summer Illumination (lx) Illumination Illumination (lx) (lx) Illumination (lx) occurred when the air caps were attached to the entire window surface 1). However, Illumination (lx) Illumination (lx) External Lighting control:(Case Power the cooling Illumination (lx) External External Lighting control: Lighting control: Power Power Illumination (lx) External Lighting control: Power External Lighting control: Power Illumination (lx) Illumination (lx) Illumination (lx) External Lighting control: Power Illumination (lx) External Lighting control: Power External Lighting control: Power External Lighting control: Power External Lighting control: Power External Lighting control: Power Power External Lighting control: Case Case Case Case Case Case Illuminance Case Case Case Case Case Case Illuminance (lx) light number (dimming level) Consumption (kWh) Illuminance Illuminance (lx) (lx) light number light (dimming number level) (dimming Consumption level) Consumption (kWh) (kWh) (lx) light number (dimming level) Consumption (kWh) Illuminance (lx) light number (dimming level) Consumption (kWh) Illuminance (lx) light number (dimming level) Consumption (kWh) Min. Ave. Illuminance (lx)(lx) light number (dimming level) Consumption (kWh) Min. Min. Ave. Ave. Illuminance (lx) Ave. light number (dimming level) Consumption (kWh) Min. and heating energy(lx) consumption was lower in all (dimming cases except Case 6, in (kWh) which no air caps were Min. Ave. Illuminance (lx) light number (dimming level) Consumption (kWh) Illuminance (lx) light number (dimming level) Consumption (kWh) Illuminance light number (dimming level) Consumption (kWh) Min. Ave. Illuminance number level) Consumption Min. Ave. Min. Ave. Min. Ave. Min. Ave. Min. light Ave. Min. Ave. attached. When the air caps were only attached to a part of the window surface (Cases 2, 3, 4, and 5), 80,000 76.0 285.1 1(8) + 3(8) + 2(3) 80,000 80,000 76.0 285.1 76.0 285.1 1(8) + 3(8) + 2(3) 1(8) + 3(8) + 2(3) 80,000 76.0 285.1 1(8) + 3(8) + 2(3) 80,000 76.0 285.1 1(8) 3(8) 2(3) 80,000 76.0 285.1 1(8) 3(8) 2(3) 80,000 76.0 285.1 1(8) 3(8) 2(3) 80,000 76.0 285.1 1(8) 3(8) 2(3) 80,000 76.0 285.1 1(8) ++ 3(8) ++ 2(3) 80,000 76.0 285.1 1(8) ++ 3(8) ++ 2(3) 80,000 76.0 285.1 1(8) ++ 3(8) ++ 2(3) 80,000 76.0 285.1 1(8) ++ 3(8) ++ 2(3) 0.642 11 11 0.642 0.642 11 11 0.642 0.642 0.642 0.642 0.642 1 0.642 0.642 1 0.642 1 1 0.642 the cooling and heating energy consumption decreased by 2.0% to 21.9% for summer and by 8.3% 70,000 66.1 188.2 1(8) 3(8) 2(5) 70,000 70,000 66.1 188.2 66.1 188.2 1(8) + 3(8) + 2(5) 1(8) ++ 3(8) ++ 2(5) 70,000 66.1 188.2 1(8) ++ 3(8) ++ 2(5) 70,000 66.1 188.2 1(8) 3(8) 2(5) 70,000 66.1 188.2 1(8) 3(8) 2(5) 70,000 66.1 188.2 1(8) 3(8) 2(5) 70,000 66.1 188.2 1(8) +++ 3(8) +++ 2(5) 70,000 66.1 188.2 1(8) + 3(8) + 2(5) 70,000 66.1 188.2 1(8) ++ 3(8) ++ 2(5) 70,000 66.1 188.2 1(8) 3(8) 2(5) 70,000 66.1 188.2 1(8) + 3(8) + 2(5) to 27.5% for 80,000 winter when compared with Case 6. the summer simulation, the cooling energy 80,000 78.8 311.3 1(8) ++ 3(8) ++ 2(3) 80,000 80,000 78.8 311.3 78.8 311.3 1(8) + In 3(8) + 2(3) 1(8) ++ 3(8) ++ 2(3) 78.8 311.3 1(8) ++ 3(8) ++ 2(3) 80,000 78.8 311.3 1(8) 3(8) 2(3) 80,000 78.8 311.3 1(8) 3(8) 2(3) 80,000 78.8 311.3 1(8) 3(8) 2(3) 80,000 78.8 311.3 1(8) 3(8) 2(3) 80,000 78.8 311.3 1(8) + 3(8) + 2(3) 80,000 78.8 311.3 1(8) ++ 3(8) ++ 2(3) 80,000 78.8 311.3 1(8) + 3(8) + 2(3) 80,000 78.8 311.3 1(8) + 3(8) + 2(3) 22 22 0.630 0.630 22 22 0.630 0.630 0.630 from 0.630 0.630 2 0.630 0.630 2 0.630 2 2 0.630 consumption notably increased in Case 4, in which the air caps were attached a0.630 height of 1.8 m 70,000 68.4 202.2 1(8) 3(8) 2(4) 70,000 70,000 68.4 202.2 68.4 202.2 1(8) + 3(8) + 2(4) 1(8) ++ 3(8) ++ 2(4) 70,000 68.4 202.2 1(8) ++ 3(8) ++ 2(4) 70,000 68.4 202.2 1(8) 3(8) 2(4) 70,000 68.4 202.2 1(8) 3(8) 2(4) 70,000 68.4 202.2 1(8) 3(8) 2(4) 70,000 68.4 202.2 1(8) +++ 3(8) +++ 2(4) 70,000 68.4 202.2 1(8) + 3(8) + 2(4) 70,000 68.4 202.2 1(8) ++ 3(8) ++ 2(4) 70,000 68.4 202.2 1(8) 3(8) 2(4) 70,000 68.4 202.2 1(8) + 3(8) + 2(4) above the floor to the top of82.2 the window. In 339.9 the winter simulation, heating energy consumption 80,000 82.2 339.9 1(8) ++ 3(8) ++ the 2(2) 80,000 80,000 339.9 82.2 1(8) + 3(8) + 2(2) 1(8) ++ 3(8) ++ 2(2) 80,000 82.2 339.9 1(8) ++ 3(8) ++ 2(2) 80,000 82.2 339.9 1(8) 3(8) 2(2) 80,000 82.2 339.9 1(8) 3(8) 2(2) 80,000 82.2 339.9 1(8) 3(8) 2(2) 80,000 82.2 339.9 1(8) 3(8) 2(2) 80,000 82.2 339.9 1(8) + 3(8) + 2(2) 80,000 82.2 339.9 1(8) ++ 3(8) ++ 2(2) 80,000 82.2 339.9 1(8) + 3(8) + 2(2) 80,000 82.2 339.9 1(8) + 3(8) + 2(2) 0.591 33 33in Case 0.591 0.591 33 33 increased 0.591 0.591 0.591 0.591 0.591 notably 3, in which the air caps were attached from a0.591 height of 1500 mm above 3 0.591 3 0.591 3 3 70,000 70.2 224.4 1(8) 3(8) 2(3) 0.591 70,000 70,000 70.2 224.4 70.2 224.4 1(8) + 3(8) + 2(3) 1(8) ++ 3(8) ++ 2(3) 70,000 70.2 224.4 1(8) ++ 3(8) ++ 2(3) 70,000 70.2 224.4 1(8) 3(8) 2(3) 70,000 70.2 224.4 1(8) 3(8) 2(3) 70,000 70.2 224.4 1(8) 3(8) 2(3) 70,000 70.2 224.4 1(8) +++ 3(8) +++ 2(3) 70,000 70.2 224.4 1(8) + 3(8) + 2(3) 70,000 70.2 224.4 1(8) ++ 3(8) ++ 2(3) 70,000 70.2 224.4 1(8) 3(8) 2(3) 70,000 70.2 224.4 1(8) + 3(8) + 2(3) the floor to the top of the window. Therefore, the proposed window-mounted air cap roller module may effectively reduce the cooling and heating energy consumption even if the air cap coverage area is adjusted to permit viewing through the window and to allow light into the room. Additionally, the module enables an occupant to choose the level of viewing possible through the window and reduces the cooling and heating energy consumption, depending on the circumstances. When considering only the reduction in total energy consumption, the best method for applying the window-mounted air cap roller module proposed in this paper is that of Case 1, in which air caps were attached to the entire window surface; however, that case did not allow viewing through the window. However, the energy consumed did decrease as the air cap coverage area was reduced, as shown in Figure 7. The energy consumption dramatically increased in Case 4 during the summer and in Case 3 during the winter. Therefore, considering the energy savings and viewing performance, the optimal height for the air cap module is 1.5 m. This is the height at which occupants can still see through the windows and energy consumption is significantly decreased.
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Table 10. Lighting device control and power consumption for maintaining appropriate indoor illumination. Summer
Energies 2018, 11, x FOR PEER REVIEW
Case 1
External
Illumination (lx)
11 of 15
Power
Lighting control:
Consumption (kWh) light number (dimming level) (lx) Table Illuminance 11. Air conditioner power required to maintain appropriate indoor temperature Min. consumption Ave. for each case. 80,000 76.0 285.1 1(8) + 3(8) + 2(3) 70,000
66.1
188.2
80,000
78.8
311.3 202.2 Case 1
Summer
0.642
1(8) + 3(8) + 2(5) 1(8) + 3(8) + 2(3)
Case 1(8) +23(8) +Case 2(4) 3
Case 4
0.630 Case 5
Case 6
80,000 82.2 (kWh) 339.9 1.955 Power consumed by air conditioner 3
1(8) + 3(8) +2.129 2(2) 2.072
2.483
2.599 0.591
2.653
Reduction 80,000 of energy consumption in 483.2 84.7 4 70,000the case without 73.1 air cap243.7 26.3% comparison with attachment (Case 6)87.5 80,000 509.2
1(8) + 3(8) +19.8% 2(3) 21.9%
6.4%
0.589 2.0%
-
2
Electrical Power Consumption 70,000 68.4 70,000
5 6
70.2
224.4
70,000
74.9
251.9
80,000
90.4
559.2 280.2 Case 1
Electrical Power Consumption 70,000 76.1
Power consumed by air conditioner (kWh) Illumination (lx)
External Case Reduction of energy in Illuminance (lx) consumption Min.
Winter
Winter
2.595
270.3
1(8) + 3(8) + 2(1) 1(8) + 3(8) 1(8) + 3(8) + 2(3)
0.552
1(8) + 3(7)
Case 1(8) +23(8) +Case 2(3) 3 2.665
3.095
Case 4
0.528 Case 5
Case 6
3.195
3.370
3.676
Ave.
Lighting control: light number (dimming level)
3727.5
1(3) 1(8) + 3(1)
comparison with the case without air cap 29.4% 30,000 386.2 5130.4 attachment (Case 6) 1 20,000
1(8) + 3(8) + 2(3)
27.5%
15.8%
Power Consumption (kWh)
13.1%
8.3%
-
0.192
30,000 391.5 5257.1 1(3) 0.168 2 When considering only the reduction in total energy consumption, the best method for applying 20,000 274.1 3800.2 1(8)
the window-mounted air cap 401.7 roller module is that of Case 1, in which air caps 30,000 5391.8proposed in this paper 1(2) 3 0.140 289.4 4065.9 however, that case 1(7) did not allow viewing through the were attached 20,000 to the entire window surface; 30,000 the energy 407.2 5474.5 window. However, consumed did decrease as the1(1) air cap coverage area was reduced, as 0.114 4 20,000 284.5 4140.3 1(6) shown in Figure 7. The energy consumption dramatically increased in Case 4 during the summer and 30,000 409.6 5680.5 in Case 3 during the winter. Therefore, considering the energy1(1) savings and viewing performance, the 5 0.105 20,000 293.1 4546.2 1(5) optimal height for the air cap module is 1.5 m. This is the height at which occupants can still see 30,000 415.8 5800.1 1(1) 6 0.092 through the windows is significantly 20,000 and energy 292.2 consumption 4695.6 1(4)decreased.
Figure Figure7.7.Evaluation Evaluationofofperformance performanceininterms termsofofreducing reducingenergy energyconsumption consumptionby bylighting lightingdevice deviceand and air conditioner for each case. air conditioner for each case.
4. Conclusions A window-mounted air cap sheet roller module was proposed and evaluated to address the impairment of viewing caused by the application of air caps on windows while still reducing building energy consumption. The proposed module was first designed as an air cap attachment module that allowed the air cap sheet to be rolled up and secured with Velcro™ tape. An insulation bar was used
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Table 11. Air conditioner power consumption required to maintain appropriate indoor temperature for each case. Summer Electrical Power Consumption
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Power consumed by air conditioner (kWh) Reduction of energy consumption in comparison with the case without air cap attachment (Case 6)
1.955
2.072
2.129
2.483
2.599
2.653
26.3%
21.9%
19.8%
6.4%
2.0%
-
Winter Electrical Power Consumption
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Power consumed by air conditioner (kWh) Reduction of energy consumption in comparison with the case without air cap attachment (Case 6)
2.595
2.665
3.095
3.195
3.370
3.676
29.4%
27.5%
15.8%
13.1%
8.3%
-
4. Conclusions A window-mounted air cap sheet roller module was proposed and evaluated to address the impairment of viewing caused by the application of air caps on windows while still reducing building energy consumption. The proposed module was first designed as an air cap attachment module that allowed the air cap sheet to be rolled up and secured with Velcro™ tape. An insulation bar was used to resolve the gap between the air caps and window glass surface caused by the attachment of the air caps to the window frame. A performance evaluation of the proposed model was then completed using a full-scale test bed. Lighting energy consumption increased by 4.3% to 17.8% in summer and by 12.3% to 52.1% in winter compared with the case in which no air caps were attached; therefore, the use of air cap sheets is not appropriate for reducing the lighting energy consumption. Heating and cooling energy, however, were significantly decreased through the use of the module. The greatest reduction in heating and cooling energy usage was found when the air caps were attached to the entire window surface (Case 1). However, when the air caps were only attached to part of the window surface (Cases 2, 3, 4, and 5), the cooling and heating energy consumption decreased by 2.0% to 21.9% for the summer and by 8.3% to 27.5% for the winter compared with Case 6, indicating that the proposed window-mounted air cap roller module was effective. Cooling energy consumption notably increased during the summer in Case 4, in which the air caps were attached from a height of 1800 mm above the floor to the top of the window. Heating energy consumption notably increased during winter in Case 3, in which the air caps were attached from a height of 1.5 m above the floor to the top of the window. Therefore, the air caps may be attached to the entire surface of a window to reduce the energy consumption but may also be effectively attached from the top of the window to a height of 1500 mm above the floor to allow viewing through the window, while still reducing the amount of energy consumed. Therefore, the window-mounted air cap roller module may enable a building occupant to choose the level of viewing secured through windows and reduce the cooling and heating energy consumption, depending on the circumstances. The proposed window-mounted air cap roller module allowed air caps to be conveniently attached to a window while resolving the problem of the impairment of views caused by the attachment of air caps onto the entire window surface. However, the performance evaluation in this study was carried out in an artificial environment by controlling specific variables. Further studies may be needed to overcome this limitation by considering various variables, such as air cap dimensions, heat transmission coefficient, time lag, material properties, and the effectiveness of air cap applications under different climate characteristics. In addition, although this study was conducted to improve viewing through a window when air caps were attached, the view from an indoor space depending on various external environmental conditions was not analyzed. Therefore, further studies may also be needed to analyze the views through windows from an indoor space.
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Author Contributions: H.L. developed main idea of the current study, performed and interpret the analysis, and wrote the manuscript. J.S. reviewed the paper. All authors have read and approved the final manuscript. Acknowledgments: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) [grant numbers NRF-2018R1C1B4A01018660, NRF-2018R1A2B2007165]. Conflicts of Interest: The authors declare no conflict of interest.
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