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Tariq, M.A.U.R.; Mohammed, A.; Ng, A.; , .; Rad, H. Cooling Loads of Buildings and Shading Devices. Encyclopedia. Available online: https://encyclopedia.pub/entry/21173 (accessed on 05 September 2024).
Tariq MAUR, Mohammed A, Ng A,  , Rad H. Cooling Loads of Buildings and Shading Devices. Encyclopedia. Available at: https://encyclopedia.pub/entry/21173. Accessed September 05, 2024.
Tariq, Muhammad Atiq Ur Rehman, Aiman Mohammed, Anne Ng,  , Hooman Rad. "Cooling Loads of Buildings and Shading Devices" Encyclopedia, https://encyclopedia.pub/entry/21173 (accessed September 05, 2024).
Tariq, M.A.U.R., Mohammed, A., Ng, A., , ., & Rad, H. (2022, March 30). Cooling Loads of Buildings and Shading Devices. In Encyclopedia. https://encyclopedia.pub/entry/21173
Tariq, Muhammad Atiq Ur Rehman, et al. "Cooling Loads of Buildings and Shading Devices." Encyclopedia. Web. 30 March, 2022.
Cooling Loads of Buildings and Shading Devices
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This entry is adapted from the peer-reviewed paper 10.3390/su14073775

It is estimated that almost 40% of the world’s energy is consumed by buildings’ heating, ventilation, and air conditioning systems. This consumption increases by 3% every year and will reach 70% by 2050 due to rapid urbanisation and population growth. In Darwin, building energy consumption is even higher and accounts for up to 55% due to the hot and humid weather conditions. Singapore has the same weather conditions but less energy consumption, with only 38% compared to Darwin. Solar radiation can be defined as electromagnetic radiation emitted by the Sun and the Darwin area receives a large amount of solar radiation. Windows that are capable of blocking excessive radiation can improve the cooling load of a building. In contrast, windows and other façades with high transmission values can increase the cooling load

building energy modeling (Revit) building energy efficiency cooling load solar shading devices

1. Introduction

In today’s world, around 40% to 50% of electricity is consumed by buildings [1][2], with 30% consumed by HVAC systems [3]. The World Health Organization (WHO) indicated that “cities will house 50% of the world’s population by 2050, rising to 70% by 2050. This urbanization and population growth will result in an increase in building energy consumption” [4][5]. Many elements can influence a building’s performance or energy demand, and if managed properly, energy demand can be significantly lowered. Building components and envelopes are to blame for the high cooling energy demand. Occupant behavior, operating hours, and the number of appliances inside the structure can all raise the amount of energy consumed [6].
Windows that are capable of blocking excessive radiation can improve the cooling load of a building. In contrast, windows and other façades with high transmission values can increase the cooling load [7]. However, these are not the only factors when it comes to heat gained from solar radiation. The Sun angle, time, and location also play a crucial role in emitting radiation [8]. The cooling load of a building air-conditioned space can be divided into two main categories: internal heat gain and external heat gain. Internal heat gain originates from the occupants, electric lighting, computers, and other equipment [9]. In a climate zone such as Victoria, with a hot summer and cold winter [10], the summer sun is high and lower in winter. However, these windows also present the opportunity to utilise the natural light indoors, precisely eliminating the artificial source of light and saving building energy loads. Many authors suggest that natural light inside buildings during the day improves residents’ health and visual comfort [11].
Allowing the required amount of light into buildings and eliminating excessive lighting is tricky and requires a plan to install shading or tinting windows to a certain amount. The extra glare of sunlight can be controlled by applying internal, external shading, or electrochromic technology. Studies were done to measure the glare index and daylight factor in a simulation program design-builder and suggested the optimal level of light in a building [12][13].
In reality, lighting quality is not directly measurable but is an emergent state created by the interplay of the lit environment and the person in that environment. Veitch et al. [14], who investigated the determinants of lighting quality, mentioned that “one cannot measure quality in the same sense as one measures length, mass, or lumen output, and lighting quality can only be assessed using behavioral measures.” Consequently, it cannot be measured directly, as indicated by [14]; however, as mentioned, it was estimated using behavioral measures. It is emphasised that this method is a simple, practical method since no real person was involved in the study.
Depending on the panel setup, neighboring panels can cast shadows over lower panels in the same system. This issue typically only arises for in-ground installations. Panels can actually be shaded by the roof they are on. Depending on the sun’s angle and the time of day, different parts of a roof (such as a chimney or dormer) can block sunlight to certain panels. Therefore, we cannot discuss shade without mentioning clouds. Despite the fact that clouds do technically block out the sun and cast shade, the clouds still let some sunlight through, which means solar panels still can produce energy, albeit at a lower efficiency. The shaded solar panels produce less power than those in direct sunlight. Exposure to less powerful sunlight is the obvious contributor to lowered efficiency, but the design of a solar installation, specifically, the panels and their inverter(s), also matters. This research constitutes a relatively new area that has emerged from this solar energy system that can be used at any time when the sun is shining; however, more electrical power can be expected when the sun is very bright and shines directly on the PV module. Shading is one of the aspects that can have an impact on PV systems. Many academics have studied the usage of bypass diodes in shading scenarios, but the fact is that shading must be thoroughly analysed and avoided since it can lead to a breakdown of the shaded module.

2. Reducing the Cooling Loads of Buildings Using Shading Devices

Shading devices are part of the solar control façade systems defined in the same standards, and their installation has become mandatory for some public buildings as a result of the 2015 revisions to the regulations. A common shading device is one that generates a pleasant indoor environment by appropriately regulating or blocking incoming solar radiation, thereby reducing the cooling or heating load of the room and selectively allowing natural lighting and vistas. Although sunshine through window glass helps to reduce heating demands in the winter, it can create a large rise in cooling loads in the summer due to indoor heat gain from solar radiation. As a result, by using shade devices and supplementing the weak parts of windows in the summer, it is feasible to cut energy consumption while still creating a comfortable indoor environment [15].
Several studies on shading devices have previously been undertaken, and the existing literature can be summarised as follows: Al-Tamimi and Fadzil [16] investigated the feasibility of using shade devices to reduce the temperature of tropical high-rise residential structures. They used simulations to examine ideal external shading devices that can minimise incoming heat and hence improve energy usage, with a focus on Malaysia’s hot and humid climate and the internal temperature control effect for high-rise residential structures. Kim et al. [17] conducted an energy simulation utilising a computer model designed for Korean residential structures based on practicality in order to introduce ideal external shading devices via comparative research on the thermal performances of residential building external shading devices. Palmero-Marrero and Oliveira [18] studied the effect of a louvred sunshade system, evaluated the performance of shading devices based on orientations and conditions, and analysed the effects of the louvred sunshade system that change depending on a variety of parameters. Kim et al. [19] investigated the cooling and heating energy consumption of Korean office buildings when horizontal shading devices or Venetian blinds were utilised, as well as optimal shading devices based on areas and orientations. Lee et al. [20] conducted a climate index development study utilising local weather data in order to understand the features of the local climate in the early design stage and confirm the validity of shading devices that can be judged by the user. Kim et al. [21] investigated cooling load reductions by analysing the reduction of cooling loads in office buildings with a high cooling load in order to confirm the effect of an effective shading device design on office buildings.
A. Gagliano et al. [22] investigated the cooling load of a lecture hall in the hot, humid climate of Malaysia. They used insulation materials PASB (polyethylene aluminum single bubble) on the external wall and simulated the insulation material with CFD software using collected data for a one-year duration. A reduction of 3 °C was achieved using the insulation materials, resulting in a lower cooling load requirement. A. Gustavsen et al. [23] also installed polyurethane on the outer side of a house wall and achieved a 28% reduction in the house’s cooling load. Another study was undertaken in Hong Kong by J.-W. Lee et al. [24], which involved applying polystyrene on the external and internal walls of the building; they achieved a 38% reduction in cooling load.
These experiments support the idea that installing low-U-value materials on the wall helps to minimise the cooling load of buildings. The contribution from windows is considered to be one of the most effective factors of heat gain/loss in buildings. Z. Yang et al. [25] claimed that up to 60% of building energy loss is due to windows with a 30% window to wall ratio (WWR) of a two-story building. Moreover, by decreasing the WWR to 20%, the energy loss was 45%. Other factors of window heat loss are the thermal conductance of window material; a better insulating window with a minimum U-value can significantly reduce these losses [26].
Subsequently, it was found that double-glazed windows are 50% more efficient than single-pane windows and have a very long life [27]. Though this technology is getting more common daily, many modern versions are being designed and evaluated for their performances. Among the current versions is aerogel fitted, vacuum, and PCMs fitted glazing. Aerogel is a world-class insulating material that is employed in the space industry due to its extreme insulation properties and delicate nature. It is a costly material, but scientists are trying to reduce its manufacturing costs. Aerogel is placed between two layers of glass; with it being very lightweight, the increase in mass of the window structure is a minor concern. According to C. Buratti and E. Moretti [28], aerogels are available in various transparencies, ranging from fully transparent to translucent to opaque, with variations in their costs. The aerogels were tested; it was found that their heat transfer coefficient is extremely low, having a value of 0.013 W/m2K [29]. Since aerogels are available in two types, known as monolithic and granular, an investigation was done by J. L. Aguilar-Santana et al. [30] and C. Buratti and E. Moretti [28] to compare both types. It was concluded that monolithic is much better in terms of its solar transmittance in the form of light and insulation ability, with an overall U-value of 0.60 W/m2K.
Khoroshiltseva et al. [31] developed a multiobjective evolutionary design technique for optimising shading devices included in refurbishment kits for an existing residential structure in Madrid. Singh et al. [32] evaluated the effect of increased shadow transmittance values on the energy and visual performance of an office building. The research was carried out at Shillong, which is characteristic of chilly climates in India. A variety of glass and internal roller shade combinations were simulated for south-, west-, north-, and east-facing offices with varied window sizes, glazing qualities, and shading methods. Eom et al. [33] discriminated between periods when shade devices are required and periods when they are not required by calculating the balance point temperature using simulations, and they constructed shading devices based on the periods split in this way. As a result, they offered a specification for ideal shading devices within the size range of shading devices specified by solar altitude, as well as a quantitative basis for projection length based on annual heating and cooling demands. Kim et al. [34] used IES 5.5.1 to analyse annual cooling and heating loads, as well as the amount of sunlight on the living room floor surface, and assessed the effects of movable horizontal shading devices to assess the impact of a new type of movable horizontal shading device on the indoor thermal environment and solar access performance.
Kim et al. [35] used the e-Quest program to evaluate the shading coefficient applied to energy-saving building envelope technology of office buildings and the loads of different types of horizontal shading devices according to orientations, and analysed the envelope elements according to orientations. Kim and Yoon [36] conducted a quantitative assessment of the various façades by taking into account the physical properties of the envelope components that can be selected in the envelope design, calculating annual loads through simulation, particularly with respect to the combination of windows and fixed external shading devices, and analysing the design suitability. Using a building energy analysis tool, Song et al. [37] investigated the complete solar irradiation of the vertical glass surface dependent on the length of the horizontal shading device according to the orientations affecting the perimeter boundary in office buildings in Seoul. Kim [38] conducted a study to derive improvement methods of solar radiation control standards of windows and shading devices based on an analysis of researchers' countries and other countries’ related standards by analysing the current status of major countries’ energy-saving design standards of buildings and performing a comparative analysis of them with the national standards and investigating complementary elements for the national standards and necessary amendments.
Shading systems are created as part of the building to prevent unwanted daylight that would cause high internal temperatures and unwanted lighting, as well as to reduce the additional operating expenses of the building system. Such as shading system strengthens the shading system of the building and establishes the design capabilities in order to adapt to the user [39].
Shading devices are classed as interior or outdoor shading devices based on where they are installed. Venetian blinds and roll screens are examples of interior shading devices, while louvres, light shelves, and awnings are examples of external shading devices [40]. Furthermore, shading devices can be characterised as fixed, manual, or movable based on how they operate [41]. Shade devices come in a variety of materials, sizes, and shapes, and can be installed in a variety of locations within a building, such as windows or as part of the architecture [42].
Because they move in line with the direction of the sun, movable awnings perform better in terms of daylight control in different seasons [43]. Fixed shading devices, on the other hand, are more suitable for implementation, particularly in Iran, where there are economic concerns and the employer accepts a more economical plan, and it also costs less to implement, in addition to being easier to design and implement.
The height of the sun and the azimuth when the shadow is required decide the fixed shading design [44]. On the one hand, horizontal shadows have the largest effect on the south side, and the length of the ridge is determined by taking into account the sun’s altitude angle. Azimuth, on the other hand, is a significant consideration for vertical shading that is utilised on the east or west side of a building where the solar height is low. It is effective to insert vertical fins at small distances to boost the protection speed while shortening the protrusion length. Regardless of the orientation, eggcrate-shaped shadows merge vertically and horizontally, taking into consideration both solar and azimuthal heights. However, one downside is that the function of natural light is lost as a result of overprotection [45].

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Muhammad Atiq Ur Rehman Tariq
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Anne Ng
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Hooman Rad
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Update Date: 19 Apr 2022
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