The Effect of Using Horizontal Shading Elements on the Energy Efficiency of Multistory Residential Buildings

Shading elements have been considered to be an important element in controlling the amount of heat and sunlight entering the spaces, the most common kinds of horizontal shading devices include architectural components including balconies, louvres, and roof overhangs. Residential buildings consume high energy by household appliances from air conditioning, which makes it the most energy consuming building. Therefore, the aim of this research is determine the effect of using horizontal shading elements on the energy efficiency of multi-storey residential buildings. DesignBuilder is a tool used in this research to evaluate the energy efficiency by comparing the typical room without shading elements and with typical room with shading elements with different depths under two district climatic conditions cold semi-arid climate and hot arid climate. The research found that energy saving between 0.5% to 30.8% when using horizontal shading elements depending on the orientation and location of the case study beside the depth of shading elements.


Introduction
Reducing energy usage has been a top priority for at least the past ten years due to the effects of global warming brought on by carbon dioxide emissions [1].The energy efficiency of a structure has a considerable impact on the two occupants' comfort and the environment, the comfort and energy efficiency of a building are greatly impacted by window systems and control components like shading devices [2].
A shading device is one of the many, both new and ancient, technologies that are available for reduce energy [1].As they diminish solar radiation, external shading elements on a building's façade are a crucial component of passive design [3].In order to improve thermal comfort and save a lot of energy, shading devices block solar radiation from entering the building in the summer while allowing the necessary solar gains in the winter [4].
Windows without shade can let a lot of solar radiation into a structure, which can lead to thermal issues and visual issues like glare that can affect how comfortable a user is [5].In hot and humid regions, it is necessary to shield interior spaces from radiation of solar that might enter the building's walls, raising the cooling load's energy requirements [1].Making effective use of solar energy can have a big impact on how energy-efficient a structure is [5].Energy use for artificial lighting, heating, and cooling 1283 (2024) 012010 IOP Publishing doi:10.1088/1755-1315/1283/1/012010 2 is impacted by shadings [6].Understanding a shading device's shadowing behavior is essential to determining how it will affect the building's thermal efficiency and its residents' comfort [5].
Many studies deal with the study of shading elements.Despite studies showing the advantages of exterior shade devices, many of them are only made for aesthetic reasons without taking full advantage of their high capacity to minimize solar radiation and glare [7].
The study of Leu et al. [1] exploring the Sketch-UP extension tool called Shadow Projector V.7 by TIG, this study intends to examine the numerous shading types found in Phnom Penh's contemporary architecture and assess various elements of various shading techniques in relation to shadow quality, the findings demonstrate that horizontal louvers suspended from deep overhangs define shading devices on contemporary buildings in Phnom Penh.The façades also feature egg-crate designs, slanted fins, and vertical fins.The aim of the study of Heidarzadeh et al. [6] was to recommend an improved design strategy for horizontal shade devices when they are placed, one that accounts for the potential energy consumption that may occur if the device is installed, the results appeared that when lighting control was used to compute annual energy consumption, it was discovered that the reduction in air conditioning, fans, and lighting energy consumption resulted in a decrease in overall energy consumption.The goal of the study of Koç et al. [8] was to make a thorough assessment by taking multiple factors into account at once in order to identify fixed external SD scenarios that are energyefficient and can be applied in office buildings, all scenarios' main energy consumption values were computed using the DesignBuilder program, The result was the identification of energy-efficient scenarios.The purpose of the study of Shahdan et al. [7] was to examine, using computer simulations, how different configurations of exterior shading devices affect energy consumption of a case study, Building Information Modeling (BIM) using the Autodesk Revit program is used as a simulation tool in this study, the results reveal that alternative structures of shade devices significantly affect how much energy they consume, with egg-crate shading devices being the optimal option.
Fixed shading elements are still employed in building design as a crucial and practical component, even if just minimal adjustments were made to the way these devices were created [8].Therefore, this study aims to determine the impact of using horizontal shading elements on efficiency of energy in multistory residential buildings, the study will be in both locations, Duhok / Iraq which its climate is cold semiarid as well as Cairo/ Egypt which its climate is hot arid.The research assumes that horizontal shading elements has an effect on efficiency of energy in multi-story residential buildings.This study will examine a typical bedroom that exists in residential building with multistory, under cold semi-arid and hot arid climates.

The methodology
The research begins with a comparative investigation of the models of residential unit in modern residential complexes in order to identify the typical models that will be employed in this study, after that creating a geometric model, setting the study's variables, and defining the basic case for both locations, first was Duhok and second was Cairo, make a simulation of energy consumption by using the DesignBuilder software.
To find the most effective horizontal shading elements depth, the common base scenario was simulated in two phases: in the first, with a bare wall for various orientations, and in the second, with various shading device depths, such as 1.2, 1.8, and 2.4 m, in order to reach at the study's conclusions, the research compares and analyzes the findings (by table and graphs by Microsoft Excel) to identify the most efficient horizontal shading elements depth for two sites.'Figure 1'.

Shading elements systems
There are two broad categories into which shading elements might be placed, 'Figure 2'.3.1.fixed shading elements: included horizontal lovers, vertical lovers, overhangs [9], such as balconies, vertical fins, or other structures (egg-crate type) that combine horizontal and vertical designs.[10] which shield the hole and the wall from the sun and rain [9].

3.2.
Mobile shading elements: included vertical blinds, venetian blinds, roller shades, which decrease solar gains, but restrict airflow and block the view [9].Adjustable shade mechanisms can be set to react automatically to sunlight and other environmental factors or to be manually changed [10].

Louvers shading elements:
They might be fixed or be adjustable.restrict airflow to a certain amount and shield the building from solar rays [9].
The solar direction of a specific building facade will affect how effective shading devices are designed.For instance, in the summer, when sun angles are high, simple fixed overhangs are a particularly effective way to shade south-facing windows.However, during the summer's peak heat gain periods, the same horizontal device is inefficient at keeping low afternoon sun from penetrating westfacing windows [9].

Study location and climate
Experimental simulation in this study will take place in two places that have different climatic conditions, 'Figure 3', present the climatic region of the countries of two locations, where Iraq classified to three climatic regions and Egypt classified to eight regions.Case 1 depicts the location in the northern Iraqi, governorate of Duhok, climatic category cold semi-arid, and described as having a cold, rainy winter and, a hot arid summer, with a latitude 36.9°, the longitude of 42.9°, elevation above sea level 483m for the location of modern residential communities.While case 2 depicts the location in the Egypt, governorate of Cairo presented by New Cairo city, climatic category hot arid, with the latitude 30.1°, longitude 31.18° and 232m of elevation above sea level for the location of modern residential communities, 'Figure 4'.Regular daily direct radiation 5.4, 6 kWh/m 2 for Duhok and Cairo respectively, and daily global horizontal irradiation 5, 5.6 kWh/m 2 for Duhok and Cairo respectively, 'Figure 5', 'Table 1' explains climate properties for two locations which they are the same location used in another researches by the researcher to investigate how using vegetation affects energy efficiency and CO2 emission.
Climatic regions in Iraq [11] Climatic regions in Egypt

Typical residential building
Usually, the multi-story residential building contains a minimum of five floors.The buildings have four orientation even main or secondary orientation, the distribution of building either separated from each other or connected by on side of the building, 'Figure 6', each floor contain 4 or 5 flats almost gathering together as square or rectangle shape around a central core which contained at least one elevator and staircase and sometimes small sharing stores for flats, flats may share by internal courts for lighting and ventilation, each flat have two exposed elevation at least one of them has windows and usually the main elevation of the flat, the services like baths and sometimes kitchens and rarely bedrooms would be located on the opened internal courts.Sometimes flats in the same floor have different sizes and areas with a different number of bedrooms.The flat usually contained from two or three -bedrooms with the main living room, the area of flats would be from 120m 2 to 190m 2 , with the medium of the number of a family member as five-person.In this study we will take five projects from modern residential communities in each location as 'Figure 7', some of them are the same projects used in another research by researchers but in this research we will study the typical bedroom.

Dimension analysis for typical spaces
The model which was used for this study for the residential building would be a Bedroom space, which determined as a typical unit in flats, and would reach to its dimensions based on the examination of certain residential building and apartment plans from modern residential communities from two selected locations, which were Avro City project, Rami Land project, Mazi Land project, French Village project, and Grand Level project in first selected location which was Duhok, as well as Al Rehab project, Madinaty project, Jannah project, Festival Living Apartments project and Ninety Avenue project in second selected location which was Cairo, 'Figure 7', 'Figure 8', 'Table 2', which explain that these spaces may take square or rectangle shape.From the previous analysis the research reaches to dimension of a typical bedroom, the bedroom could be 4m depth and 4m width, with area 16m2, depth to width ratio was 1:1.The room could have one exposure façade to the sun with a window or two exposed façades one of them have a window and the other façade part of it exposed to sun as solid, the room might shade by the balcony with different depths.
Although in most of the previous examples the (WWR) was more than 10, for this study we assumed that the bedroom includes a window with a WWR (ratio of window to wall space) 10% to give the exposed exterior wall the most space possible, the window has a single piece of 0.006m Cl glass.a UPVC frame, with sill height 0.9m, height of window 1.3m, the depth of outside reveal 0.14m, 'Figure 9', 'Table 3'.Typical rooms were built with a conventional wall that had R-value of 0. 6m².K/W, and the remaining three walls were built at 0.12 m with an R-value of 0.436 m².K/W, Floor with the R-value of the floor l0.41 m².K/W, as shown in 'Table 4', 'Figure 10'.
As is customary in modern residential complexes in these two places, it will be assumed thus a bedroom is located on the second floor of the building, the ceiling height of the room is 2.7 m, the height of the building above ground level is 0.9 m.

Study Equipment and Procedures
In this research, a computer simulation employing was the application DesignBuilder V 6.1 in the experimental study.This software's energy plus simulation engine is used to produce performance data.By estimating yearly energy consumption, loads for heating and cooling, the program used in this study explores energy savings of adopting horizontal shading features.
Determine the location of the base case study site using the file with weather data, then define the 3D geometry of the building and type (residential), along with the use of the base case space (a bedroom), and the construction of the building, such as its floor, walls, and ceiling, along with its doors and windows: determine the WWR for the opening, the type of glass, and the window frame for the wall that had the opening, then determine the layers of construction for the last three walls, floor, and roof.Then determine the climate of the space (the HVAC system), including the infiltration rate, which was 0.300 ac/h, internal gain, and the split-unit heating and cooling system, which used electricity from the grid and had a seasonal CoP of 2.340.The temperature for heating was 21°C, the set point for the heating thermostat (the required temperature for heating) had been 18°C, while the required temperature for cooling had been 24°C, the set point for the cooling thermostat (the required temperature for cooling) was 28°C.Identify the area's function and the population there.
For instance, the bedroom had a density of 2 people per square meter (0.125) while the living room had a density of 5 people per square meter (0.2083).It was taken into account to determine the holiday, which was a 19-day break in each area.Establish the occupancy schedule and operation as the occupancy ratio for the summer and winter weekdays 'Table 5'.
Lighting was assumed to be a Led lighting source, therefore, the lighting effect was neglected.From January 1 to December 31, a simulation was created for the entire year.To calculate the load of cooling and heating in kWh, the fuel total in terms of annual energy consumption, simulations are used.The output of energy usage is displayed as graphs and tables by use Microsoft Excel 2016 in order to make graphs and conduct comparative evaluation of several scenarios using the simulation's overall data.

Study Variable and Constant
The variables included in the base case were space with different shading device depth such as (1.2, 1.8, 2.4) m, analyzed using eight distinct façade orientations (primary and secondary orientation), orientation of site (declination in the direction of 0° which presented a North direction to 315° which presented a North West direction with step 45° from one orientation to another.The constancies which are included in the base case test were first: WWR for the external façade which was 10%, second: components for the room's remaining three walls, floor and ceiling.

Energy efficiency experimental modeling
First-phase simulation of the standard case for each orientation in two separate locations in terms of annual energy consumption uses bare walls, for bedroom 'Table 6', 'Figure 11'.The minimum annual energy consumption was in S orientation which was 27.6 kWh/m 2 for case 1 and in N orientation which was 23.9 in case 2. The maximum annual energy consumption was in W orientation which was 43.1 kWh/m2 for case1 and 35.5 kWh/m2 in SW orientation for case 2.  Second phase situation simulation for different shading elements depth, for each orientation with variable depth (1.20, 1.80, and 2.40) m applied on eight orientations, 'Figure 12', 'Figure 13', to get the most efficient shade element depth of comparison for every orientation in term of annual energy consumption of annual energy in both locations with the greatest reduction when compared to the base case of bedroom.

Annual energy consumption for typical bedroom in Duhok
The saving in energy consumption for North orientation was from 0.5% by using a horizontal shading element with width 2.4m to 1.1% by using horizontal shading element with depth 1.2m.The saving in energy consumption was from 7.9% for North East orientation, by using a horizontal shading element with width 1.2m to 11.1% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 12.8% for East orientation, by using a horizontal shading element with width 1.2m to 20.2% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 19.8% for South East orientation, by using a horizontal shading element with width 1.2m to 22.3% by using horizontal shading element with depth 1.8m.The saving in energy consumption was from 17.0% for South orientation, by using a horizontal shading element with width 2.4m to 26.1% by using horizontal shading element with depth 1.2m.The saving in energy consumption was from 25.3% for South West orientation, by using a horizontal shading element with width 1.2m to 29.2% by using horizontal shading element with depth 1.8m and 2.4m.The saving in energy consumption was from 14.9% for West orientation, by using a horizontal shading element with width 1.2m to 25.5% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 9.6% for North West orientation, by using a horizontal shading element with width 1.2m to 14.4% by using horizontal shading element with depth 2.4m, 'Figure 14', Table 7'.

Annual energy consumption for typical bedroom in Cairo
The saving in energy consumption for North orientation was from 1.1% by using a horizontal shading element with width 1.2m to 1.5% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 7.0% for North East orientation by using a horizontal shading element with width 1.2m to 9.1% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 13.1% for East orientation by using a horizontal shading element with width 1.2m to 18.6% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 19.8% for South East orientation by using a horizontal shading element with width 1.2m to 22.8% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 24.6% for South orientation by using a horizontal shading element with width 1.2m to 27.0% by using horizontal shading element with depth 1.8m.The saving in energy consumption was from 24.2% for South West orientation by using a horizontal shading element with width 1.2m to 30.8% by using horizontal shading element with depth 1.8m and 2.4m.The saving in energy consumption was from 16.1% for West orientation by using a horizontal shading element with width 1.2m to 25.4% by using horizontal shading element with depth 2.4m.The saving in energy consumption was from 9.7% for North West orientation by using a horizontal shading element with width 1.2m to 13.7% by using horizontal shading element with depth 2.4m, 'Figure 15', Table 8'.

Results discussion
After comparing between annual energy consumption by using different horizontal shading elements depth, from the analyzed compared results with each location and with two locations together which obtained from the experimental study to reach to the most effective horizontal shading element depth for each location, and by comparing the energy consumption for each shading element depth with base case (bare wall) in eight different façade orientations, it was found that there is an energy saving when using them and that agree with the study of Shahdan et al. [7] which found that the energy usage is significantly reduced by shading devices.The energy saving was different according the shading depth in each orientation, 'Table 9'.The simulation appeared that the effective shading device depth for most orientation for bedroom in first location Duhok was 2.4m except South East and South West orientation which was 1.8m and North, South orientation which was 1.2m, the effective shading device for bedroom was 2.4m in all orientation in second location Cairo except South orientation which was 1.8m.
By examining how horizontal shading elements are used in cold semi-arid and hot arid climates, it was discovered that this study offers more diverse options at the start of building design for varied climates and varied orientation, in order to improve energy efficiency.The results agree with the study of Leu et al. [1] which its findings were useful to designers in optimizing shading device shadowing behavior, especially with regard to building orientation.

Conclusions
By examining how horizontal shading elements are used in cold semi-arid and hot arid climates, it was discovered that this study offers more diverse options at the start of building design for varied climates in order to improve energy efficiency.
This study found that adopting various horizontal shading elements in various orientations and climates resulted in changes in annual energy use.The most energy-efficient placement of horizontal shading elements is on the South East with depth 1.8m, South with depth 1.2m, West with depth 2.4m, South East with depth 1.8m for rationalization of annual energy consumption in cold semi-arid climate, and in South West with depth 2.4m, South with depth 1.8m, West with depth 2.4m and South east with depth 2.4m for rationalization of annual energy consumption in hot arid climate.
The efficiency of energy consumption in multistory residential structures is improved by the use of horizontal shading components for an annual period.The use of horizontal current components with a northerly direction in cold semi-arid, and hot arid climates does not seem to have much benefit, as the energy consumption in this direction is very small and almost negligible.
By comparing using horizontal shading elements in first location Duhok and second location Cairo it concluded using horizontal shading element in North East, East, West and North West orientation in Duhok were more effective than using them in the same orientation in second location Cairo while using horizontal shading elements in North, South East, South, South West orientations in Cairo were more effective than using them in the same orientation in first location Duhok for the same typical bedroom.
Adding horizontal shading element was more effective in saving energy for first and second location, because of its ability to reduces the entry of heat from the sun into the building, in addition to preventing direct solar rays from entering the building.

Future researches
The study is limited to simulate horizontal shading elements only, the future study could apply vertical and composite shading elements to find out their impact on saving energy.

[ 12 ] 3 .
Figure Climatic regions in two different countries Iraq and Egypt.

Figure 6 .
Figure 6.Explain the buildings distribution in modern residential communities [Researchers].

Figure 8 .
Figure 8. Explain living and bedrooms for typical apartments in Duhok and New Cairo city [Researchers].

Figure 9 .
Figure 9. Explain the typical bedroom dimensions which concluded from dimension analysis plan and interior façade.

5 10 .
th layer Gypsum plaster 0.02 m 0.51 W/m.k 960 J/kg.K 1120 Kg/m 3 R-Value = 0.417 m².K/W U-Value = 2.397 W/ m².K The components of exterior walls Internal wall components Internal floor and ceiling components Figure The components of the exterior and internal walls, floor, and ceiling [15],[16].

Figure 11 .
Figure 11.Annual energy consumption for bedroom in two separate locations with various orientations [Researchers].

Figure 14 .
Figure 14.Annual energy consumption with different shading device depth for bedroom in first location Duhok.[Researchers]

Figure 15 .
Figure 15.Annual energy consumption with different shading device depth for bedroom in second location Cairo.[Researchers]

Table 2 .
Analysis of the dimensions of bedrooms in modern residential communities

Table 5 .
Schedule of the bedroom's use.

Table 6 .
A comparison of energy consumption for bedroom with area 16m² for different orientations.

Table 7 .
Annual energy saving with different shading device depth for bedroom in Duhok.

Table 8 .
Annual energy saving with different shading device depth for bedroom in Cairo.

Table 9 .
The most efficient saving horizontal shading element depth for each orientation for the typical bedroom.